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As described in an accompanying paper, trinitrophenyl (TNP) modification of pork insulin (PI) at the A1 glycine position allows this molecule to stimulate a proliferative response in H-2b (B10) mice. We now show that this antigen stimulates low IgG responses in the same strain of mice. Our results show that T-cell help and proliferation may therefore be regulated independently. [ABSTRACT FROM AUTHOR]

MRL-lpr mice and their congenic counterparts MRL- + spontaneously develop an autoimmune disease that resembles systemic lupus erythematosus in humans. The two strains, although congenic, differ by a considerable number of disease parameters, reflecting the expression of the lpr autosomal recessive gene. One paradox that has developed out of the work utilizing the congenic mice is that the gene responsible for lymphoproliferation also appears to be responsible for the inability of T cells to respond to proliferative signals in vitro. In this paper we investigated a possible lpr gene-encoded macrophage defect in these mice. It was found, however, that both the MRL- + and MRL-lpr mice failed to divide in response to Con A, the lack of division correlating with an inability to secrete the growth promoter interleukin-2. In MRL- + mice and young MRL-lpr mice this non-responsiveness was corrected by the addition of normal CRA PEC. The defect could not be explained by a failure of M RL- + or M RL-lpr peritoneal exudate cells to quantitatively or qualitatively provide a source of interleukin-1 to Con A-activated T cells or by the possibility that the peritoneal exudate cells were blocked in their function by the presence of sera-derived autoantibodies and/or immune complexes on their membranes. We postulate that the inability of T cells to proliferate in MRL congenic mice can be explained by two defects: (i) the failure of antigen-presenting cells in MRL- + and MRL-lpr to provide the necessary signals to immunocompetent T cells, this defect not being associated with the lpr gene, and (ii) the lpr gene controlled outgrowth of a unique T-cell population that cannot respond in our assay system. [ABSTRACT FROM AUTHOR]

Summary The bacterial superantigen exotoxins of Staphylococcus aureus and Streptococcus pyogenes are potent stimulators of polyclonal T-cell proliferation. They are the causes of toxic shock syndrome but also induce CD25+ FOXP3+ regulatory cells in the CD4 compartment. Several studies have recently described different forms of antigen-induced regulatory CD8+ T cells in the context of inflammatory diseases and chronic viral infections. In this paper we show that bacterial superantigens are potent inducers of human regulatory CD8+ T cells. We used four prototypic superantigens of S. aureus (toxic shock syndrome toxin-1 and staphylococcal enterotoxin A) and Str. pyogenes (streptococcal pyrogenic exotoxins A and K/L). At concentrations below 1 ng/ml each toxin triggers concentration-dependent T-cell receptor Vβ-specific expression of CD25 and FOXP3 on CD8+ T cells. This effect is independent of CD4+ T-cell help but requires antigen-presenting cells for maximum effect. The cells also express the activation/regulatory markers cytotoxic T-lymphocyte antigen-4 and glucocorticoid-induced tumour necrosis factor receptor-related protein and skin homing adhesins CD103 and cutaneous lymphocyte-associated antigen. Superantigen-induced CD25+ FOXP3+ CD8+ T cells were as potent as freshly prepared naturally occurring CD4+ regulatory T cells in suppressing proliferation of CD4+ CD25− T cells in response to anti-CD3 stimulation. Although superantigen-induced CD8+ CD25+ FOXP3+ express interleukin-10 and interferon-γ their suppressive function is cell contact dependent. Our findings indicate that regulatory CD8+ T cells may be a feature of acute bacterial infections contributing to immune evasion by the microbe and disease pathogenesis. The presence and magnitude of regulatory CD8+ T-cell responses may represent a novel biomarker in such infections. Superantigen-induced regulatory CD8+ T cells also have therapeutic potential. [ABSTRACT FROM AUTHOR]

Peripheral blood CD4 CD45RO T cells activated in vitro are able to induce expression of tumour necrosis factor-α (TNF-α) in monocytes via a contact-dependent mechanism. Activation is achieved either with interleukin-2 (IL-2)/IL-6/TNF-α over an 8-day period or cross-linking CD3 using anti-CD3 antibody for 48 hr. In this paper, we show that the p38 mitogen-activated protein kinase (MAPK) signalling pathway played different roles in the generation of effector function in these two types of activated T cells. In anti-CD3 activated T cells, p38 MAPK is a negative regulator for anti-CD3 induced cell proliferation and has no significant effect on the acquisition of either the effector function (induction of monocyte-derived TNF-α) or production of T-cell cytokines. In contrast, the p38 MAPK signalling pathway is required for the acquisition of cytokine-induced effector function and promotes cell proliferation and cytokine production. [ABSTRACT FROM AUTHOR]

MRL-+, MRL-lpr and B6-lpr have been shown to be useful models in studying systemic lupus erythematosus. MRL-lpr and B6-lpr differ from their congenic counterparts by the presence and expression of the homozygous recessive lymphoproliferation (Ipr) gene. One manifestation of this gene is a massive Tall proliferation that results in a generalized lymphadenopathy in older animals. A paradox that has developed out of the work utilizing the congenic mice is that the gene responsible for lymphoproliferation also appears to be responsible for the inability of T cells to respond to proliferative signals in vitro. In this paper we investigate the basis for this hypo responsiveness in antigen-induced activation of proliferation and antibody synthesis. We have demonstrated that spleen cells from both MRL-+ and MRL-lpr mice gave minimal stimulation in a one-way mixed lymphocyte reaction against allogeneic T cells. These findings were extended to include antigen-specific proliferation involving antigen that must be processed and presented to responder lymphocytes in a H-2 restricted manner. Thus, MRL- + and MRL-lpr spleen cells pulsed with ferredoxin also failed to stimulate ferredoxin-primed T cells from B10.Br animals in vitro. We then investigated whether any T-cell defect(s) was also contributing to this proliferative hyporesponsiveness. T lymphocytes from the spleen of MRL- +, 2-month-old MRL-lpr, and 6-month-old MRL-lpr were tested in a one-way mixed lymphocyte reaction. It was found that only the MRL- + T cells gave responses approaching normal, suggesting lpr gene involvement in T-cell non-responsiveness. This was confirmed by the demonstration of an age-onset T-cell proliferative hyporesponsiveness in B6. lpr mice. This lpr gene-linked non-responsiveness was also shown to extend to T-cell helper function in a positive allogeneic effect assay. We can conclude from these studies that antigenic non-responsiveness in MRL congenic mice can be explained by two defects: (i) the failure of antigen-presenting cells in MRL- + and MRL-lpr mice to provide the necessary signal(s) to immunocompetent T cells, this defect not being associated with the lpr gene, and (ii) the Ip gene controlled outgrowth of a unique T-cell population that cannot respond in our assay systems. [ABSTRACT FROM AUTHOR]

In the autologous Theileria mixed leucocyte reaction (MLR), irradiated Theileriaparva-infected cells induce proliferative responses in autologous peripheral blood mononuclear leucocytes (PBM)II irrespective of the immune status of the donor animal. In this paper we have analysed the cellular basis of this response in naive and immune cattle to determine the Thelleria specificity of the response. The magnitude of proliferation is dependent on two parameters, namely the presence or absence of monocytes in the responder population, and the phenotype of the parasitized stimulator cells, both of which appeared to be independent of the immune status of the donor animal. Monocyte-depleted responders invariably gave stronger proliferative responses but generated cytotoxicity from immune cattle that tended to be less genetically restricted. Marked differences were observed in the stimulatory capacity of cloned parasitized T-cell and non-T cell lines. At least part of this variation was associated with differences in the capacity of the parasitized cells to secrete soluble suppressive factors and possibly also stimulatory factors. Two observations indicated that, in immune cattle, part of the proliferative response in the autologous Theileria MLR is parasite-specific. First, stimulator cells fixed with glutaraldehyde stimulated proliferative responses in monocyte-depleted PBM from immune animals but not naive animals. Second, in autologous Theileria MLRs with intact PBM, genetically restricted cytotoxic cells were generated from immune but not naive animals. While inonocytes seem not to be required for induction of the parasite-specific component of the response, their absence from the assay when viable stimulator cells are utilized appears to enhance the non- specific component of the proliferative and cytotoxic responses. [ABSTRACT FROM AUTHOR]

In this paper we describe the first in vitro response to the liver alloantigen F. The anti-F response serves as a valuable model for autoimmune phenomena since priming appropriate strains of mice (responders) with allogeneic but not syngeneic type F leads to autoantibody production. The in vitro system is based on the proliferation of T cells, from mice primed in vivo with F, when coincubated with splenic adherent cells (SAC) prepulsed with F in vivo. The system displays two important correlates of the in vivo antibody response to F:1.T cells from mice primed with syngeneic F do not proliferate when incubated with SAC prepulsed with syngeneic F and 2. Mice that do not make antibody responses to allo F in vivo (DBA/2) do not show in vitro proliferative responses. These findings indicate that the proliferative assay is a good in vitro model for the F response. [ABSTRACT FROM AUTHOR]

Plaque-forming cell responses and antibody titres to sheep red cells (SRC) were elevated in normally-fed irradiated adult mice reconstituted with spleen cells from young mice which had received a 4% albumin diet, compared with those given cells from normally-fed littermates. This was independent of the dose of cells transferred (5 × 106-4 × 107), the day of assay (3–10) and the duration of protein-deficiency (1 or 3 weeks). It suggests that the depressed responses produced by protein-deficient (donor) mice reported in earlier papers resulted from an impairment of reticuloendothelial function or a shortage of protein reserves, not directly associated with the spleen. As protein-deficiency (of the donor) accelerated the initiation of the adoptive response and increased the cell yields of the recipients it is considered likely that an enhancement of cell proliferation during the first 3-5 days after transfer was responsible for the elevated responses. [ABSTRACT FROM AUTHOR]

This paper describes experiments under-taken to determine more uniform conditions for the generation of cytotoxic lymphokine -- 'lymphotoxin' (LT) in differently stimulated rat lymphocyte cultures, and to compare the sensitivity of different test systems for detecting rat LT activity in vitro. Wistar rat lymphoid cells were activated by culture with phytohaemagglutinin (PHA) and mixed lymphocyte cultures (MLC) with semi-allogeneic (Wistar × August) F1 lymphoid cells. Lymphocyte supernatants harvested between 1 and 8 days were tested for theft effect on the metabolism and viability of cultured mouse fibroblasts (L-929 cells) by four methods: (i) inhibition of [14C]leucine incorporation; (ii) total and viable cell counts in test tube cultures ('macro test'); (iii) viable cell counts in microtitre plates ('micro test'); and (iv) chromium (51Cr) release from chromated L-cell monolayers. Cytotoxic effects on target cells of lymphocyte supernatants were evident after 3 days of PHA stimulation and 6 days of mixed lymphocyte culture, and the most sensitive indication of cytotoxic activity provided by inhibition of amino-acid incorporation and by loss of viable L cells from monolayers in tube cultures. In dilutions greater than 1:16-1:32 both cytotoxic supernatants exhibited a stimulating effect on target-cell proliferation. Stimulation of L cells growth was also observed when monolayers were exposed for 24 h to 'early' (24 h) PHA undiluted supernatants, At a later time of exposure to these supernatants a considerable loss of total and viable cells in the monolayers was evident. The results indicated that both cytotoxic and growth-stimulating lymphokines could be generated during activation of rat lymphocytes. A hypothesis is suggested whereby `lymphotoxin' activity in vitro arises from the sequential effects of stimulating and cytotoxic lymphokine, and whereby the balance of these effects in vivo might determine the response of fibroblasts involved in reactions of chronic allergic inflammation. [ABSTRACT FROM AUTHOR]

This paper describes the immunoregulatory effects of interleukin-10 (IL-10) on synovial cells in vitro. Synovial cells were cultured with IL-10 in the presence or absence of various cytokines. Following incubation, the costimulatory molecule expression on synovial cells and cytokine production in culture supernatants were analysed by an indirect immunofluorescence method and enzyme-linked immunosorbent assay, respectively. We also examined the effect of IL-10 on the function of synovial cells as antigen-presenting cells (APC). Synovial cells spontaneously express several kinds of costimulatory molecule and produce various kinds of cytokines. Stimulation of synovial cells with interferon-γ (IFN-γ), IL-lβ, or 12-O-tetradecanoyl phorbol 13-acetate (TPA) markedly enhanced the expression of costimulatory molecules and cytokine production of these cells. Both spontaneous and up-regulated costimulatory molecule expression and cytokine production were significantly suppressed by the addition of IL-10. Autologous T-cell proliferation was stimulated by purified protein derivative (PPD) in IFN-γ-treated synovial cells and treatment of these synovial cells with IL-10 also suppressed T-cell, proliferation. Our results suggest that IL-10 has an inhibitory effect on synovial cells and is an important immunoregulatory component of the cytokine network in rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

The bone marrow of young adult nude mice was investigated as a site of antibody formation after intravenous immunization with the thymus-independent antigen Escherichia coli lipopolysaccharide (LPS). Mice heterozygous for the nu-gene were found to be capable of a plaque-forming cell (PFC) response in both spleen and bone marrow after primary and secondary immunization with LPS. Primary immunization of nude mice with LPS induced a normal PFC response in the spleen, but did not evoke the appearance of PFC in the bone marrow. During the secondary response the nude mice did show PFC activity in the bone marrow, but at a much lower level than their heterozygous littermates. At all time points after secondary immunization the number of splenic PFC was higher in nude mice than in the control mice. Determination by immunofluorescence of cells containing cytoplasmic immunoglobulin (C-Ig cells) in the bone marrow of young adult nonimmune nude and heterozygous mice, revealed a three times higher number of C-IgM cells in the bone marrow of the heterozygous thymus-bearing mice. On the other hand, the number of splenic C-IgM cells was higher in the nude mice than in their heterozygous littermates. These results suggest that the presence of the thymus facilitates the appearance of mature antibody-forming cells in the bone marrow of young adult mice, irrespective of whether the generation of these cells is initiated by so called thymus-dependent or thymus-independent antigens. [ABSTRACT FROM AUTHOR]

Summary: Interleukin‐22 (IL‐22) is a potential therapeutic agent for diseases driven by epithelial injury. To characterize the IL‐22 expressed by rhesus macaques, animals that are irreplaceable for human disease research, rhesus macaque IL‐22 (rhIL‐22) was cloned and expressed, and its biological activity and in vivo distribution were examined. It was found that the rhIL‐22 gene consists of five introns and six exons, including a short non‐coding exon starting 22 bp downstream of a putative TATA box. The amino acid sequence of rhIL‐22 showed 95·5% identity to that of humans, and it shared two conserved disulphide bonds, three N‐glycosylation sites and all the critical residues for binding to IL‐22R1. High levels of IL‐22 mRNA were observed in the liver, pancreas, lymphoid tissues and especially in the outer‐body barriers such as the intestinal tract of rhesus macaques. Functionally, purified rhIL‐22 has a similar but a little earlier effect on signal transducer and activator of transcription 3 phosphorylation at Tyr705 compared with that of commercial human IL‐22. The expression of the antibacterial proteins β‐defensin‐2, S100A8, S100A9, RegIIIα and Muc1 by HT‐29 cells was largely upregulated after stimulation with rhIL‐22. Recombinant rhIL‐22 could also significantly promote the proliferation of human intestinal epithelial cells without affecting cell apoptosis. These data indicate that rhesus macaque IL‐22 is highly similar to that of humans in both structure and function, and tests of therapeutic effects of human IL‐22 on human diseases in rhesus macaques are warranted. [ABSTRACT FROM AUTHOR]

Thalidomide (TM) has been reported to have anti-cancer and antiinflammatory properties, and dexamethasone (DX) is known to reduce inflammation and inhibit production of inflammatory cytokines. Many studies have reported that combinatorial therapy with TM and DX is clinically used to treat multiple myeloma and lupus nephritis, but the mechanism responsible for its effects has not been elucidated. In this study, we determined that TM and DX co-treatment had an enhanced immunemodulatory effect on T cells through regulating the expression of co-stimulatory molecules. Splenic naive T cells from C57BL/6 mice were sort-purified and cultured for CD4+ T cell proliferation and regulatory T (Treg) cell conversion in the presence of TM and/or DX. Following incubation with the drugs, cells were collected and OX40, 4-1BB, and glucocorticoid- induced tumour necrosis factor receptor-related protein (GITR) expression was quantified by flow cytometry. TM (1 or 10 µM) decreased CD4+ T cell proliferation in a dose-dependent manner, whereas TM/DX (0.1 or 1 nM) co-treatment further decreased proliferation. Treg cell populations were preserved following drug treatment. Furthermore, expression of co-stimulatory molecules decreased upon TM/DX co-treatment in effector T (Teff) cells and was preserved in Treg cells. Splenic CD4+ T cells isolated from TM- and DX-treated mice exhibited the same patterns of Teff and Treg cell populations as observed in vitro. Considering the selective effect of TM on different T cell subsets, we suggest that TM may play an immunomodulatory role and that TM/DX combinatorial treatment could further enhance these immunomodulatory effects by regulating GITR, OX40, and 4-1BB expression in CD4+ T cells. [ABSTRACT FROM AUTHOR]

CD4 T cells help immune responses, but knowledge of how memory CD4 T cells are regulated and how they regulate adaptive immune responses and induce immunopathology is limited. Using adoptive transfer of virus-specific CD4 T cells, we show that naive CD4 T cells undergo substantial expansion following infection, but can induce lethal T helper type 1-driven inflammation. In contrast, memory CD4 T cells exhibit a biased proliferation of T follicular helper cell subsets and were able to improve adaptive immune responses in the context of minimal tissue damage. Our analyses revealed that type I interferon regulates the expansion of primary CD4 T cells, but does not seem to play a critical role in regulating the expansion of secondary CD4 T cells. Strikingly, blockade of type I interferon abrogated lethal inflammation by primary CD4 T cells following viral infection, despite that this treatment increased the numbers of primary CD4 T-cell responses. Altogether, these data demonstrate important aspects of how primary and secondary CD4 T cells are regulated in vivo, and how they contribute to immune protection and immunopathology. These findings are important for rational vaccine design and for improving adoptive T-cell therapies against persistent antigens. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis inhibits optimal T helper type 1 (Th1) responses during infection. However, the precise mechanisms by which virulent M. tuberculosis limits Th1 responses remain unclear. Here, we infected dendritic cells ( DCs) with the virulent M. tuberculosis strain H37Rv or the attenuated strain H37Ra to investigate the phenotypic and functional alterations in DCs and resultant T-cell responses. H37Rv-infected DCs suppressed Th1 responses more strongly than H37Ra-infected DCs. Interestingly, H37Rv, but not H37Ra, impaired DC surface molecule expression ( CD80, CD86 and MHC class II) due to prominent interleukin-10 ( IL-10) production while augmenting the expression of tolerogenic molecules including PD-L1, CD103, Tim-3 and indoleamine 2,3-dioxygenase on DCs in a multiplicity-of-infection (MOI) -dependent manner. These results indicate that virulent M. tuberculosis drives immature DCs toward a tolerogenic phenotype. Notably, the tolerogenic phenotype of H37Rv-infected DCs was blocked in DCs generated from IL-10−/− mice or DCs treated with an IL-10-neutralizing monoclonal antibody, leading to restoration of Th1 polarization. These findings suggest that IL-10 induces a tolerogenic DC phenotype. Interestingly, p38 mitogen-activated protein kinase ( MAPK) activation predominantly mediates IL-10 production; hence, H37Rv tends to induce a tolerogenic DC phenotype through expression of tolerogenic molecules in the p38 MAPK- IL-10 axis. Therefore, suppressing the tolerogenic cascade in DCs is a novel strategy for stimulating optimal protective T-cell responses against M. tuberculosis infection. [ABSTRACT FROM AUTHOR]

Co-receptors, being either co-stimulatory or co-inhibitory, play a pivotal role in T-cell immunity. Several studies have indicated that CD43, one of the abundant T-cell surface glycoproteins, acts not only as a potent co-receptor but also as a negative regulator for T-cell activation. Here we demonstrate that co-stimulation of human peripheral blood (PB) T cells through two distinct CD43 epitopes recognized by monoclonal antibodies (mAb) CD43-6E5 (T6E5-act) and CD43-10G7 (T10G7-act) potently induced T-cell proliferation. However, T-cell co-stimulation through two CD43 epitopes differentially regulated activation of nuclear factor of activated T cells (NFAT) and nuclear factor- κB (NF- κB) transcription factors, T-cell cytokine production and effector function. T6E5-act produced high levels of interleukin-22 (IL-22) and interferon- γ (IFN- γ) similar to T cells activated via CD28 ( TCD28-act), whereas T10G7-act produced low levels of inflammatory cytokines but higher levels of regulatory cytokines transforming growth factor- β (TGF- β) and interleukin-35 (IL-35). Compared with T6E5-act or to TCD28-act, T10G7-act performed poorly in response to re-stimulation and further acquired a T-cell suppressive function. T10G7-act did not directly inhibit proliferation of responder T cells, but formed stable heterotypic clusters with dendritic cells (DC) via CD2 to constrain activation of responder T cells. Together, our data demonstrate that CD43 is a unique and polarizing regulator of T-cell function. [ABSTRACT FROM AUTHOR]

Proliferation of rapidly dividing bone marrow-derived cells is strongly dependent on the availability of free glutamine, whose uptake is mediated through different amino acid transporters. The sodium-coupled neutral amino acid transporter (SNAT) family was previously reported to be associated with the development of collagen-induced arthritis in mice. Here, we tested the hypothesis whether impairment of SNAT proteins influences immune cell function and in turn alters arthritis development. The 2-(methylamino)isobutyric acid (MeAIB), a SNAT-specific substrate, was used to modulate the function of SNAT proteins. We demonstrate that glutamine uptake by murine naive lymphocytes, and consequent cell proliferation, is strongly associated with system A transporters. Physiological impairment of SNAT proteins reduced the antibody-initiated effector phase of arthritis, mainly by affecting the levels of circulating monocytes and neutrophils. MeAIB was also shown to affect the proliferation of immortalized cells, through trans-inhibition of SNAT proteins. Based on our observations, we conclude that SNAT proteins regulate the initial stages of lymphocyte activation by regulating glutamine uptake, and that the effector phase of arthritis can be affected by non-metabolized SNAT substrates. Most probably, metabolically active cells within both the adaptive and the innate immune systems are regulated by SNAT proteins and play a role in modifying arthritis development. [ABSTRACT FROM AUTHOR]

CD8 T cells used in adoptive immunotherapy may be manipulated to optimize their effector functions, tissue-migratory properties and long-term replicative potential. We reported that antigen-stimulated CD8 T cells transduced to express an active form of the transcription factor signal transducer and activator of transcription 5 ( STAT5 CA) maintained these properties upon adoptive transfer. We now report on the requirements of STAT5 CA-expressing CD8 T cells for cell survival and proliferation in vivo. We show that STAT5 CA expression allows for greater expansion of T cells in vivo, while preserving dependency on T-cell-receptor-mediated tonic stimulation for their in vivo maintenance and return to a quiescent stage. STAT5 CA expression promotes the formation of a large pool of effector memory T cells that respond upon re-exposure to antigen and present an increased sensitivity to γc receptor cytokine engagement for STAT5 phosphorylation. In addition, STAT5 CA expression prolongs the survival of what would otherwise be short-lived terminally differentiated KLRG1-positive effector cells with up-regulated expression of the senescence-associated p16 INK4A transcripts. However, development of a KLRG1-positive CD8 T cell population was independent of either p16 INK4A or p19 ARF expression (as shown using T cells from CDKN2A−/− mice) but was associated with expression of transcripts encoding p15 INK4B, another protein involved in senescence induction. We conclude that T-cell-receptor- and cytokine-dependent regulation of effector T cell homeostasis, as well as mechanisms leading to senescent features of a population of CD8 T cells are maintained in STAT5 CA-expressing CD8 T cells, even for cells that are genetically deficient in expression of the tumour suppressors p16 INK4A and p19 ARF. [ABSTRACT FROM AUTHOR]

Basophils are known to modulate the phenotype of CD4+ T cells and to enhance T helper type 2 responses in vitro and in vivo. In this study, we demonstrate that murine basophils inhibit proliferation of CD4+ T cells in autologous and allogeneic mixed lymphocyte reactions. The inhibition is independent of Fas and MHC class II, but dependent on activation of basophils with subsequent release of interleukin-4 ( IL-4) and IL-6. The inhibitory effect of basophils on T-cell proliferation can be blocked with antibodies against IL-4 and IL-6 and is absent in IL-4/ IL-6 double-deficient mice. In addition, we show that basophils and IL-4 have beneficial effects on disease activity in a murine model of acute graft-versus-host disease (Gv HD). When basophils were depleted with the antibody MAR-1 before induction of Gv HD, weight loss, Gv HD score, mortality and plasma tumour necrosis factor levels were increased while injection of IL-4 improved Gv HD. Basophil-depleted mice with Gv HD also have increased numbers of CD4+ T cells in the mesenteric lymph nodes. Our data show for the first time that basophils suppress autologous and allogeneic CD4+ T-cell proliferation in an IL-4-dependent manner. [ABSTRACT FROM AUTHOR]

Myeloid dendritic cells ( mDC) are key mediators of innate and adaptive immunity to virus infection, but the impact of HIV infection on the m DC response, particularly early in acute infection, is ill-defined. We studied acute pathogenic simian immunodeficiency virus ( SIV) infection of rhesus macaques to address this question. The m DC in blood and bone marrow were depleted within 12 days of intravenous infection with SIVmac251, associated with a marked proliferative response. In lymph nodes, m DC were apoptotic, activated and proliferating, despite normal m DC numbers, reflecting a regenerative response that compensated for m DC loss. Blood m DC had increased expression of MHC class II, CCR7 and CD40, whereas in lymph nodes these markers were significantly decreased, indicating that acute infection induced maturation of m DC in blood but resulted in accumulation of immature m DC in lymph nodes. Following SIV infection, lymph node m DC had an increased capacity to secrete tumour necrosis factor- α upon engagement with a Toll-like receptor 7/8 ligand that mimics exposure to viral RNA, and this was inversely correlated with MHC class II and CCR7 expression. Lymph node m DC had an increased ability to capture and cleave soluble antigen, confirming their functionally immature state. These data indicate that acute SIV infection results in increased m DC turnover, leading to accumulation in lymph nodes of immature m DC with an increased responsiveness to virus stimulation. [ABSTRACT FROM AUTHOR]

Summary Chronic antigenic stimulation leads to gradual accumulation of late-differentiated, antigen-specific, oligoclonal T cells, particularly within the CD8+ T-cell compartment. They are characterized by critically shortened telomeres, loss of CD28 and/or gain of CD57 expression and are defined as either CD8+CD28− or CD8+CD57+ T lymphocytes. There is growing evidence that the CD8+CD28− (CD8+CD57+) T-cell population plays a significant role in various diseases or conditions, associated with chronic immune activation such as cancer, chronic intracellular infections, chronic alcoholism, some chronic pulmonary diseases, autoimmune diseases, allogeneic transplantation, as well as has a great influence on age-related changes in the immune system status. CD8+CD28− (CD8+CD57+) T-cell population is heterogeneous and composed of various functionally competing (cytotoxic and immunosuppressive) subsets thus the overall effect of CD8+CD28− (CD8+CD57+) T-cell-mediated immunity depends on the predominance of a particular subset. Many articles claim that CD8+CD28− (CD8+CD57+) T cells have lost their proliferative capacity during process of replicative senescence triggered by repeated antigenic stimulation. However recent data indicate that CD8+CD28− (CD8+CD57+) T cells can transiently up-regulate telomerase activity and proliferate under certain stimulation conditions. Similarly, conflicting data is provided regarding CD8+CD28− (CD8+CD57+) T-cell sensitivity to apoptosis, finally leading to the conclusion that this T-cell population is also heterogeneous in terms of its apoptotic potential. This review provides a comprehensive approach to the CD8+CD28− (CD8+CD57+) T-cell population: we describe in detail its origins, molecular and functional characteristics, subsets, role in various diseases or conditions, associated with persistent antigenic stimulation. [ABSTRACT FROM AUTHOR]

Summary Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an important component of the inflammasome, functioning as an adaptor protein that facilitates the recruitment and activation of procaspases that in turn promote the maturation of interleukin-1β (IL-1β) and IL-18. Despite initial focus on the inflammatory properties of ASC there is emerging evidence that highlights the importance of ASC in facilitating adaptive immune responses. However, the cellular and molecular basis for the involvement of ASC in adaptive immunity remains largely unexplored. We have previously demonstrated that activated ASC-deficient T cells have dampened proliferative responses. We have therefore explored the underlying cellular mechanism(s) by which ASC regulates T-cell proliferation. We show that under activating conditions (anti-CD3/CD28 stimulation) in bulk T-cell cultures the presence of ASC−/− CD4+ T cells is sufficient to suppress the proliferative responses of neighbouring T cells. Furthermore, ASC−/− CD4+ T cells upon activation exhibit a suppressive cytokine profile, with elevated production of IL-10 and reduced secretion of T helper type 1 cytokines, interferon-γ and IL-2. This increase in IL-10 secretion within the activated ASC−/− CD4+ T-cell compartment was not associated with a proportional increase in conventional Foxp3+ regulatory T (Treg) cells. Interestingly, when equal numbers of fluorescence-activated cell sorted ASC+/+ and ASC−/− Treg cells (CD4+ CD44intermediate/high CD25+) were activated in vitro, the ASC−/− fraction produced significantly more IL-10 than their wild-type counterparts, suggesting that ASC−/− Treg cells have greater suppressive capacity. Collectively, these results imply that the ASC may influence the development and functioning of Treg cells. [ABSTRACT FROM AUTHOR]

Nucleotide-binding and oligomerization domain (NOD) -like receptors (NLRs) and retinoic acid-inducible gene (RIG) -like receptors (RLRs) are recently discovered cytosolic pattern-recognition receptors sensing mainly bacterial components and viral RNA, respectively. Their importance in various cells and disorders is becoming better understood, but their role in human tonsil-derived T lymphocytes remains to be elucidated. In this study, we evaluated expression and functional relevance of NLRs and RLRs in human tonsillar CD3 T lymphocytes. Immunohistochemistry, real-time RT-PCR and flow cytometry revealed expression of NOD1, NOD2, NALP1, NALP3, NAIP, IPAF, RIG-1, MDA-5 and LGP-2 at mRNA and protein levels. Because of the limited number of ligands (iE-DAP, MDP, Alum, Poly(I:C)/LyoVec), functional evaluation was restricted to NOD1, NOD2, NALP3 and RIG-1/MDA-5, respectively. Stimulation with the agonists alone was not enough to induce activation but upon triggering via CD3 and CD28, a profound induction of proliferation was seen in purified CD3 T cells. However, the proliferative response was not further enhanced by the cognate ligands. Nonetheless, in tonsillar mononuclear cells iE-DAP, MDP and Poly(I:C)/LyoVec were found to augment the CD3/CD28-induced proliferation of tonsillar mononuclear cells. Also, iE-DAP and MDP were found to promote secretion of interleukins 2 and 10 as well as to up-regulate CD69. This study demonstrates for the first time a broad range of NLRs and RLRs in human tonsillar T cells and that NOD1, NOD2 and RIG-1/MDA-5 act synergistically with αCD3 and αCD28 to induce proliferation of human T cells. Hence, these results suggest that these receptors have a role in T-cell activation. [ABSTRACT FROM AUTHOR]

Macrophages (Mϕ) are professional antigen-presenting cells, but when they accumulate at sites of inflammation, they can inhibit T-cell proliferation. In experimental autoimmune uveoretinitis, this limits the expansion of T cells within the target organ. To define requirements for the elaboration of this outcome, we have generated populations of Mϕ in vitro that could also regulate T-cell responses; stimulating CD4+ T-cell activation and cytokine production, but simultaneously suppressing T-cell proliferation. When T cells are removed from the influence of such cells, normal T-cell responses are restored. We show that tumour necrosis factor 1 (TNFR1) signalling is a critical checkpoint in the development of such Mϕ, as TNFR1−/− Mϕ are unable to suppress T-cell proliferation. This deficit in antigen-presenting cells results in a lack of production of prostaglandin E2 (PGE2) and nitric oxide, which are critical effector mechanisms that inhibit T-cell division. However, TNFR1 signalling is not required for the inhibitory function of Mϕ because we could circumvent the requirement for this receptor, by maturing Mϕ in the presence of exogenous interferon-γ and PGE2. This produced TNFR1−/− Mϕ that inhibited T-cell proliferation and indicates that TNFR1 delivers a signal that is necessary for the development but not the execution of this function. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) are known to be essential for the induction and regulation of immune responses. Non-human primates are essential in biomedical research and contribute to our understanding of the involvement of DCs in human infectious diseases. However, no direct single-platform method for quantifying DC precursors has yet been optimized in macaques to give accurate absolute blood counts of these rare-event cell populations in the blood. We adapted a rapid whole-blood assay for the absolute quantification of DCs in cynomolgous macaques by four-colour flow cytometry, using a single-platform assay compatible with human blood. Cynomolgus macaque plasmacytoid DCs (pDCs) and CD1c+ myeloid DCs (CD1c+ mDCs) were quantified in the blood of 34 healthy macaques and the results obtained were compared with those for blood samples from 11 healthy humans. In addition, circulating absolute numbers of pDCs were quantified in cynomolgus macaques chronically infected with SIVmac. During infection, pDC counts decreased whereas circulating CD1c+ mDC counts increased. Information regarding absolute pDC and mDC counts in non-human primates may improve our understanding of the role of these cells in SIV/HIV infection and in other infectious diseases. [ABSTRACT FROM AUTHOR]

Interleukin (IL)-21 is a novel cytokine that has been shown to enhance proliferation and activation of CD8+ T cells, enhance natural killer (NK) cell activity and costimulate anti-CD40-driven B-cell proliferation in mice. Several studies have furthermore demonstrated antitumour effects of IL-21 administration in mouse models. In this study we have investigated how IL-21 affects the survival and cytotoxicity of human NK cells and modulates their expression of surface receptors and of the effector molecules granzyme B and perforin. In contrast to murine NK cells, where IL-21 alone cannot sustain survival, IL-21 and IL-2 were equally efficient in sustaining survival of human NK cells. In the absence of other cytokines, IL-21 had little effect on expression of a panel of surface receptors on human NK cells. However, IL-21 synergized with IL-2 to up-regulate several surface receptors, including NKG2A, CD25, CD86 and CD69. The CD25+ CD86+ NK cells were CD56bright and were large and granular. Expression of the effector molecules perforin and granzyme A and B was up-regulated by IL-21 at both mRNA and protein levels. Furthermore, IL-21 increased the cytotoxicity of NK cells against K562 target cells. These findings suggest that IL-21 modulates NK cell activity through induction of intracellular effector molecules as well as modulation of surface receptor expression. [ABSTRACT FROM AUTHOR]

The number and function of human T cells in the periphery are regulated by homeostatic signals received from antigen-presenting cells (APCs) and the common gamma chain (γc) cytokines interleukin (IL)-7 and IL-15. We found that, in the absence of introduced antigen, blood monocytes or myeloid dendritic cells (MDCs) in the presence of IL-7 and IL-15 (IL-7/IL-15) can regulate CD4+ T memory (Tm) cell numbers by polyclonal cell proliferation. The dynamics of CD4+ Tm cell proliferation, in the presence of IL-7/IL-15, was dependent on contact with MDCs and to a lesser extent on contact with monocytes. IL-7/IL-15 either alone or combined with monocytes or MDCs enhanced the proportion of CD4+ Tm cells with activated and effector phenotype and diminished the helper function of CD4+ Tm cells. These CD4+ Tm cells, preconditioned with IL-7/IL-15 alone or with monocytes or MDCs and IL-7/IL-15, reduced T cell-dependent immunoglobulin M (IgM) and IgG responses. This appeared to be a contact-dependent effect involving a reduction in antibody-producing CD27+ B memory cells, but contact-independent suppression by soluble factors also contributed to the antibody-producing capacity of CD27+ B memory cells. These results indicate that blood monocytes, MDCs and the cytokines IL-7/IL-15 contribute to homeostasis of CD4+ Tm cells by regulating their number, activation state and helper/suppressor (regulatory) function. In healthy individuals, this mode of regulating CD4+ Tm cell homeostasis may provide a basis for the control of autoimmune responses. [ABSTRACT FROM AUTHOR]

12F6 is a murine anti-human CD3 monoclonal antibody, which competes with OKT3 for binding to human T cells and possesses more effective T-cell suppression and activation properties compared to OKT3. It thus exhibits the potential to be developed as an immunoregulation agent for manipulating T-cell functions and preventing acute allograft rejection. In an attempt to minimize the immunogenicity of murine 12F6 (m12F6) for potential clinical application, a humanized version of 12F6, denoted as hu12F6, was successfully constructed by complementary determining region (CDR) grafting and shown to maintain both T-cell activation and suppression activities similar to m12F6. Furthermore, in order to reduce the first dose reaction syndrome caused by T-cell activation following the first administration of anti-CD3 antibodies, two amino acid mutations were introduced into the Fc region of hu12F6, resulting in the Fc-mutated 12F6 humanized antibody (hu12F6mu). This Fc-mutated version displayed a similar antigen-binding affinity and specificity compared with hu12F6 and m12F6 but with much weaker FcR binding activity. hu12F6mu was shown to be much less potent in the induction of T-cell proliferation, cytokine release (tumour necrosis factor-α, interferon-γ and interleukin-10) and early activation marker expression on the cell surface (CD69 and CD25) than parental 12F6 and OKT3 did. In contrast, hu12F6mu was effective in modulating T-cell receptor/CD3 and inhibiting mixed lymphocyte reaction with a similarity as compared to m12F6 and OKT3. In conclusion, the resultant hu12F6mu was much less mitogenic to T cells but retained potent immunosuppression, suggesting it might be an alternative to OKT3 as an immunosuppressive drug with less immunogenicity and toxicity for clinical application. [ABSTRACT FROM AUTHOR]

The CD3 antigen is a surface structure associated with the T-cell receptor (TCR) to form a complex involved in antigen recognition and signal transduction. Reports on the structures of the CD3 molecules associated withαβ- andγδ-TCR have been contradictory. To investigate this issue, we raised a panel of monoclonal antibodies (mAb) against purified porcine CD3 molecules. Unlike the conventional anti-CD3, these mAb reacted specifically with peripheralγδ-T cells, but not withαβ-T cells. Immunoprecipitation showed that the antibody recognized a subset of CD3 molecules that were associated withγδ-TCR. Also unlike the conventional anti-CD3, these mAb, though directed at two different epitope groups, failed to induce antigenic modulation, T-cell proliferation and CD3-redirected cytotoxicity. Taken together, these results suggest that there are differences in the antigenicity, signal transduction potentials and probably structural differences between the CD3 molecules expressed at the surface ofαβ- andγδ-T cells. [ABSTRACT FROM AUTHOR]

Proliferation is an essential characteristic of clonal selection and is required for the expansion of antigen reactive clones leading to the development of antibody of different isotypes and memory cells. New data for mouse and human B cells point to an important role for division in regulating isotype class and in optimizing development of protective immunity by the regulated entry of cells to the plasma cell lineage. [ABSTRACT FROM AUTHOR]

Recently, we have described a soluble survival signal for activated lymphocytes from CD14+ cells. As a result of the importance of T lymphocytes in the pathogenesis of rheumatoid arthritis (RA), we speculate a possible role for CD14+ cells in supporting the outgrowth of autoreactive lymphocytes in RA. To address this issue further, supernatants from activated CD14+ cells (CD14 cocktails) in both normal controls and RA patients were collected. The relative strength of the CD14 cocktails from normal controls and RA patients was compared. The data showed that depletion of CD14+ calls resulted in a much higher increase of activation-induced cell death (AICD) and a decrease of lymphocyte proliferation in the peripheral blood mononuclear cells of RA patients compared to normal controls. Interestingly, CD14 cocktails from RA patients provide much stronger protection against AICD compared to those from normal controls. The observed soluble survival signal from CD14+ cells is a general phenomenon because CD14 cocktails prevent both phytohaemagglutinin A-p- and anti-CD3-induced AICD. Furthermore, supernatants collected from human dendritic cell cultures also prevent activated lymphocytes from undergoing AICD. The data implicate an important role of the CD14+ cell and its secreted form of survival signal in the pathogenesis of RA. [ABSTRACT FROM AUTHOR]

Pectic polysaccharide fraction (BR-2) containing pharmacologically active pectic polysaccharide, bupleuran 2IIc, which was prepared from a medicinal herb, the roots of Bupleurum falcatum L., was administered orally to C3H/HeJ mice for 7 consecutive days. Proliferative responses of spleen cells were enhanced in the presence of the purified pectic polysaccharide, bupleuran 2IIc, but another B-cell mitogen, lipopolysaccharide (LPS) did not give a similar effect. In vitro studies using spleen cells showed that bupleuran 2IIc also stimulated lymphocytes, depleted of adherent cells or T cells. Bupleuran 2IIc treatment increased subpopulation of CD25+ and surface immunoglobulin M-positive (sIgM+) lymphocytes. Non-specific immunoglobulin secretion of spleen cells treated with bupleuran 2IIc was increased according to the culture time, and coexistence of interleukin-6 (IL-6) enhanced the secretion more than that of bupleuran 2IIc alone. These results suggest that bupleuran 2IIc proliferates B cells in the absence of macrophages, and the resulting activated B cells are then induced into antibody-forming cells in the presence of IL-6. Among the structural region of bupleuran 2IIc, ramified region (PG-1), which consists of rhamnogalacturonan core rich in neutral sugar chain, showed the potent mitogenic activity suggesting it to be an active site. Mitogenic activity of bupleuran 2IIc was reduced in the presence of antipolysaccharide antibody (antibupleuran 2IIc/PG-1-IgG), which recognizes the ramified region of bupleuran 2IIc as the antigenic epitope. Mitogenic activity of bupleuran 2IIc was also reduced by the addition of β-d-GlcpA-(1→6)-β-d-Galp-(1→6)-d-Galp or β-d-GlcpA-(1→6)-d-Galp, which are a part of the epitopes of antibupleuran 2IIc/PG-1-IgG. These results suggest that the epitopes in bupleuran 2IIc act as active sites of the polysaccharide during mitogenic activity. [ABSTRACT FROM AUTHOR]

The mouse monoclonal antibody MR6 recognizes a 200 000 MW protein (gp200-MR6), which is expressed highly on human thymic cortical epithelial cells. The antigen is also expressed on some epithelial tumours and we have previously shown that MR6 inhibits the proliferation of the colon carcinoma cell lines HT29. However, the role of this molecule in the thymus is not known. In order to generate reagents that could be used in murine thymic functional studies we isolated antibodies specific to human gp200-MR6, using a phage display library expressing single-chain (sFv) antibodies. Three independent clones were isolated by panning with purified protein and their specificity was confirmed by immunohistochemistry, Western blotting and flow cytometry. In addition to human thymus, these phage antibodies also recognized the homologous antigen in mouse, pig and other species. Expressed as soluble sFv one of these clones inhibited the proliferation of HT29 cells and a mouse thymic epithelial cell line, suggesting that this antibody exhibits similar functional activity to MR6. In fetal thymic organ culture, thymocytes recovered from thymic lobes cultured in the presence of this sFv, were reduced in number fivefold compared with the control and the majority remained at the double-negative stage of development. These data indicate that gp200-MR6 plays an important role in thymocyte development. In addition, this is the first report to demonstrate that specific sFv can be used to study, and alter, thymic development. This work also highlights the advantage of phage antibody technology in selecting such reagents for functional assays. [ABSTRACT FROM AUTHOR]

The B oligomer of pertussis toxin serves as a weak mitogen in the I lymphocyte, an effect which is associated with an early rise in cytosolic free calcium concentrations, as monitored by Fura-2 fluorescence. Upon co-administration of phorbol dibutyrate, a phorbol ester tumour promotor which activates protein kinase C, pertussis toxin-induced proliferation was synergistically enhanced, as measured by the increased uptake of[³H]thymidine, into cellular DNA. Although phorbol esterco- administration has often been associated with an inhibition of Ca2+-mobilizing pathways, phorbol dibutyrate pretreatment had no inhibitory effect on the pertussis toxin-induced calcium flux and may actually have enhanced this response slightly. Flow cytometric analysis of cell populations expanded by the combined regimen did not provide evidence for the preferential expansion of cells bearing either CD4 or CD8, the T-cell determinants representative of the helper-inducer and cytotoxic- suppressor subsets, respectively. Pertussis toxin and phorbol dibutyrate appear, therefore, to elicit polyclonal stimulation, rather than the selective activation of a given lymphocyte subset. Expression of the transferrin receptor, a marker for nutrient uptake, and CD25, the Tac component of the interleukin-2 (IL-2) receptor, was, however, synergistically enhanced in cells activated by the co- treatment procedure. [ABSTRACT FROM AUTHOR]

In several conditions in the skin, characterized by T-cell infiltration, keratinocytes are induced to synthesize and express class II transplantation antigens. The biological significance of this induced expression is still not understood. In this study, class II antigens were induced on rat ear keratinocytes by local intradermal injections into the ear of rat recombinant interferon-gamma (IFN-γ). Epidermal cell suspensions prepared from these ears contained more than 50% class II-expressing cells, as judged by immunocytochemistry, compared with less than 5% in untreated epidermis. When comparing the capacity of these to different epidermal cell populations to stimulate a syngeneic PPD specific T-helper cell line, it was found that IFN-γ-exposed epidermal cells induced a lower T-cell response to PPD than did normal epidermal cells. This discrepancy could not be explained by either an infiltration of inflammatory cells into the epidermis of IFN-γ-treated ears or by a difference in interleukin-1 production as determined in culture supernatants. The addition of indomethacin to cultures with IFN-γexposed epidermal cells restored the T-cell response to PPD to that of normal epidermal cells, suggesting an inhibitory effect of prostaglandins. Our data indicate that epidermal cells exposed to IFN-γ in vivo can suppress an antigen-specific T-cell proliferation. [ABSTRACT FROM AUTHOR]

After T-cell activation, a switch of leucocyte common antigen (LCA) expression occurs which is detected by the disappearance of CD45R and the appearance of UCHL1 positivity. Upon activation of CD45R+ T cells by phytohaemagglutinin (PHA), the IL-2 receptor (IL-2R) develops at 15 hr and blast cells enter the S phase at 20 hr, while remaining UCHL1-. At 40 hr, mitotic cells continue to express CD45R determinants, but weak UCHL1 reactivity is now detectable on 15-20% of these cells. By inhibiting the separation of daughter cells with cytochalasin D, it can be demonstrated that the UCHL1 antigen is newly synthesized in the Golgi apparatus before insertion into the membrane after the first mitosis. At 65 hr after activation, 80% of proliferating cells are UCHL1+. T cells undergo a similar development during allogeneic activation, and specific alloresponsive cells, tested in secondary mixed lymphocyte reaction (MLR), become greatly enriched among the proliferating UCHL1+ cells. Conversely, after a primary MLR, residual CD45R+ T cells are unresponsive to the original stimulus but can still proliferate in response to unrelated alloantigens. These results clarify both the time-course of the acquisition of UCHL1 antigen during the proliferative cycle of activated T cells, and indicate the shift of antigen responsive T-cell populations from the CE45R+ to the UCHL1+ pool. [ABSTRACT FROM AUTHOR]

Unstimulated human peripheral blood lymphocytes (HPBL) were found to proliferate when cultured in vitro with interleukin-2 (IL-2). In bulk long-term cultures of HPBL cultured with IL-2, cell numbers usually doubled after 8-11 days of culture, and a 10-fold increase in cell number occurred between the second and third weeks of culture. These cells retained their ability to respond to a panel of T-cell dependent antigens, phytomitogens and allogeneic cells up to Day 21 of culture. The proliferating cells predominantly expressed the T-cell antigens (CD3, CD4 and CD8), but not antigens of natural killer (NK) cells, B cells or mononuclear phagocytic cells. The proportion of cells expressing CD3 and CD4 antigens progressively increased with length of culture. Purified lymphocytes expressing either CD4 or CD8 antigens were also found to be capable of showing a proliferative response to IL-2, especially when provided with autologous accessory cells. However, purified human peripheral blood B cells expressing the Leu 12 antigen did not respond with or without autologous accessory cells. Unlike the responses to phytomitogen, soluble antigens or allogeneic cells, the proliferative responses of HPBL to IL-2 were not inhibited by a monoclonal antibody (OK-1a-1) to the non-polymorphic part of human class II histocompatibility antigens. [ABSTRACT FROM AUTHOR]

Phorbol myristate acetage (PMA) and Ca2+ ionophore A23187 mimic early signal transduction pathways and activate purified human T cells to secrete large quantities of interleukin-2 (IL-2) and to proliferate. Despite producing 50-100-fold more IL-2 than phytohaemagglutinin (PHA)-activated peripheral blood lymphocytes (PBL), PMA/A23187-stimulated human T cells proliferate less than cells activated by PHA. Washing the cells to remove PMA/A23187 was found to increase cellular proliferation two to five-fold. High-affinity IL-2R (HA-IL-2R) were found to be expressed by human T cells that had been washed 24 hr after PMA/A23187 stimulation and recultured without stimulus for an additional 48 hr, but not by T cells constantly exposed to PMA/A23187 for 72 hr. Radioligand binding studies with [125I]IL-2 demonstrated that while the α (p55) and Β (p70-75) subunits of HA-IL2R were both present on the constant PMA/A23187-stimulated T cells, they did not appear to associate to form functional HA-IL-2R. This defect in the expression of bio-active HA-IL-2R on constant PMA/A23187-stimulated human T cells seems to account for their low proliferative response. [ABSTRACT FROM AUTHOR]

Mice were primed with TNP-derivatized insulin, or TNP-Mycobacteria, and lymph node cells were challenged in vitro with haptenated and unhaptenated antigens. Using either priming antigen, T-cell proliferative responses could be obtained to TNP-insulin. In B10 (H-2b), mice, which are responders to beef insulin (BI), but not to pork insulin (PI), TNP-BI or TNP-PI primed a response to TNP beef and TNP pork insulins, and to beef but not pork insulin, suggesting that a proportion of the response was directed to the modified portion of the molecule. However, priming with BI resulted in responsiveness to TNP-PI, but not to PI. Also, TNP-BI stimulated an augmented proliferative response in BI-primed mice. These results suggest that TNP modification can alter the antigenicity of the carrier molecule, perhaps by enhancing weak interactions with MHC molecules on presenting cells. Finally, there was no evidence that the TNP-dependent response to TNP-pork insulin was down-regulated by suppressor cells directed at the carrier molecule. [ABSTRACT FROM AUTHOR]

Three stimuli were used to compare the signals necessary for interleukin (IL-2) receptor expression and IL-2 production: triggering of the T-cell antigen receptor/CD3 complex (Ti/CD3) by CD3 antibodies, activation of protein kinase C (Pi(C) by phorbol esters, and elevation of intracellular calcium levels by calcium ionophore. The salient observations were that IL2 responsiveness, which reflects IL-2 receptor expression, and Tall proliferation which requires both IL-2 production and IL-2 receptor expression, are not coordinately regulated. Firstly, a low threshold of CD3 activation or a brief (1 hr) exposure of I cells to maximal CD3 stimulation is sufficient to induce IL-2 responsiveness, but higher levels of activation for a prolonged period are necessary to ensure a Tall proliferative response. Secondly, in response to optimal 1-cell stimulation there is a short (2-4 day) period of Tall proliferation followed by a prolonged phase of IL-2 responsiveness (10-14 days). Differences in the kinetics and signalling requirements for IL-2 receptor expression and IL-2 production, regulated at the level of mRNA expression, provide a molecular basis for these observations. A major difference between induction of IL-2 production and IL-2 receptor expression is that the dual signals of calcium and PKC are necessary for IL-2 production, but a sole stimulus of PKC is sufficient for IL-2 receptor expression. Also, a low level stimulation of PKC wilt induce IL-2 receptor expression but higher levels of PKC stimulation are required for IL-2 production. As a consequence, triggering of a single receptor, namely the Ti/CD3 complex, results in IL-2 responsiveness, but an additional signal that activates P1CC is necessary for IL-2 production. These observations suggest that a Ca2+/PKC dual signal model does not explain completely the signal transduction pathways that regulate T-cell growth. Moreover, precise regulatory mechanisms have evolved to control the homeostasis of the autocrine proliferative response of a Tall population. [ABSTRACT FROM AUTHOR]

We investigated the possible existence of IL-1 in human amniotic fluid (AF). Since AF from most full- term deliveries appeared to contain an inhibitor(s) for thymocyte proliferation, AFs were fractionated by gel filtration prior to IL- 1 assay. IL-1 activities eluted in two peaks at positions of 90,000-60,000 MW and 20,000-15,000 MW. Growth inhibitory activity eluted at the position of 70,000-50,000 MW, and its effect appeared to be non-specific because these fractions inhibited the growth of various cell lines. Using isoelectric focusing (IEF) techniques, pI values of 68-7.3 for the higher MW IL-1 as well as 4.9-5.5 and 6.7-7.0 for the lower MW IL-1 were obtained. Antibody against human IL-1α partially neutralized the activity of the lower MW IL-1, though it exhibited little effect on the higher MW IL-1. In contrast, antibody against human IL-1β almost completely neutralized the activity of the higher MW IL-1 and partially neutralized the activity of the lower MW IL-1. These results suggest that most of the higher MW IL-1 is β-type, and the lower MW IL-1 is a mixture of α and β-types. IL-1 β appeared to exist as a complex (combined with AF components) or as an aggregate of the lower MW IL-1 forms. These findings indicate that both IL-1α and IL-1β are present in normal human AF from full-term deliveries, though IL-1β exists as a higher MW form aggregated with an unknown molecule. [ABSTRACT FROM AUTHOR]

Utilizing allotype-specific antibodies to immunoprecipitate RT6.2 from DA.68 rat lymphocyte lysates, we have shown this antigen recently to be composed of two related, non-glycosylated polypeptides with apparent molecular weights (MW) of 24,000 and 26,000 (reducing conditions), which evidently are anchored in the cell membrane by covalent linkage to phosphatidylinositol. The present report shows that RT6. 1 allotype-specific antibodies precipitate a more complex pattern of bands from LEW.6A rat lymphocyte lysates. These consist of an endo-F-resistant RT6.2-like 25/ 27,000 MW doublet (reducing conditions) as well as at least five additional endo-F-sensitive, endo-H- resistant polypeptides of 30,000, 32,000, 33,000, 34,000, 35,000 MW. Endo-F treatment seems to convert the additional higher to the lower molecular weight forms. In contrast to the endo-F-resistant 25/27,000 MW doublet, the higher MW forms of RT6. 1 partly bind to lentil lectin and concanavalin A (Con A). Two-dimensional electrophoretic analyses (NEPHGE/SDS-PAGE) reveal similar patterns of charge heterogeneity of the lower and higher MW forms of RT6. 1. Neuraminidase treatment does not affect the pIs of the lower MW forms but shifts the pIs of the higher MW forms to those of the lower ones. All forms of RT6. 1 evidently employ the covalent linkage to phosphatidylinositol for membrane anchorage. Identical patterns of molecular forms-the doublet for RT6.2, the polymorphic pattern for RT6. 1-are observed upon immunoprecipitation of the alloantigens from the lysates of corresponding series of inbred strains of rats with both allotype-specific antibodies and a polyclonal rabbit serum recognizing a common determinant on both alloantigens. [ABSTRACT FROM AUTHOR]

Experiments have been carried out in vitro and in vivo to determine to what extent CD8+ T cells in the rat can function independently of any helper activity from CD4+ cells. We have identified the culture conditions required for the autonomous proliferation of CD8+ T cells in the rat mixed leucocyte culture (MLC) and in particular have studied both the kinetics of the response and the effect of replacing the homologous serum, used in our previous MLC experiments, with fetal calf serum (FCS). The results obtained using FCS show that, early in the MLC, CD8+ Tails proliferate at a comparable rate to the CD4+ subset but that, within 48-72 hr, the proliferation rate of the CD8+ cells ceases to increase with time. In contrast, the proliferation of the CD4+ T cells appears to be limited only by the exhaustion of the culture medium. The results also show that the proliferative responses of both CD4+ and CD8 + T cells are inhibited in homologous serum but that it is the CD8+ subset that is more affected. When CD8+ T cells, in homologous serum, are co-cultured with irradiated CD4+ T cells the proliferative activity is increased, indicating that the helper activity of the CD4+ T cells can over-ride the inhibitory effect of the serum. In vivo we have compared the abilities of injected CD4+ and CD84 T cells to mediate rejection of skin allograft's on nude rats. Grafts were rejected more rapidly on recipients of low doses of CD4+ T cells than on rats given 200 times as many CD8+ T cells. Thoracic duct lymphocytes (TDL) obtained 5 weeks after CD8+ T-cell injection always contained a population of CD4+ T cells, even when the injected CD8+ T-cell inoculum contained less than 0. 1 % CD44 cells as contaminants. Evidence was obtained that these CD4+ T cells found in TDL displayed alloreactivity in MLC. Further, the intentional injection of very low doses of CD4+ cells led, after 5 weeks, to frequencies of CD4+ T cells, in thoracic duct lymph, equal to that obtained by the injection of 200 times as many cells of the same phenotype. It appears that, in T-cell-deficient rats, CD4+ cells can expand over 2000 times in a few weeks. Such expansion may explain the relatively slow rejection of skin allografts observed in these experiments when nude rats were injected with putatively pure populations of CD8+ T cells. Taken together the data do not support the view that rat CD8+ T cells display significant autonomy in vivo but they do show a generally low level of alloreactivity in vitro. In contrast, our results stress that CD4+ T cells are uniquely potent in their ability to provide helper activity for CD8+ T cells in vitro and to mediate graft rejection in vivo. Our data are therefore not consistent with the concept that the two subsets are functionally equivalent and differ only with respect to the class of MHC antigen to which they are responsive. [ABSTRACT FROM AUTHOR]

We have produced two CD23 monoclonal antibodies (mAb),LA1 and LA2, which differ significantly in their patterns of reactivity compared to other mAb within this cluster. Unlike other CD23 mAb, LA1 and LA2 show virtually no reactivity with freshly isolated tonsil B lymphocytes or mantle zone lymphocytes in tissue section. That LA1 and LA2 are CD23 mAb is confirmed by their precipitation of a 45,000 MW surface protein from B cells and strong reactivity with a CD23 transfectant. Cross- blocking studies with four well-characterized CD23 mAb show that LA1 and LA2 recognize the same, distinct epitope of the CD23 molecule. However, similar to other CD23 mAb, expression of LA1 and LA2 increases after activation. Following removal of cells staining with the well- characterized CD23 mAb MHM6, using a highly efficient magnetic bead technique, LA1 and LA2, but not other CD23 mAb, react with a subpopulation of the remaining cells when activated with interleukin-4 (IL-4) or phorbol ester. Soluble LAI and MHM6 both provide a co-stimulatory signal for phorbol ester-induced B-cell proliferation. This response is increased if these mAb are used to cross-link the CD23 molecule. Interestingly, despite the fact that LA2 and LA 1 cross-block, LA2 has no effect on functional responses in its soluble form but can elicit a comparable increase in proliferation when cross-linked. Results presented here suggest that the novel CD23 mAb, LA1 and LA2, recognize a distinct form of the CD23 molecule, expressed only on activation. These mAb define a subpopulation of activated B cells which do not stain with other CD23 mAb. [ABSTRACT FROM AUTHOR]

The induction of human influenza virus-specific memory cytotoxic T lymphocytes (CTL) from CTL precursors (CTLp) was investigated using limiting-dilution cultures and cell lines. Differentiation of maximal numbers of CTLp in limiting-dilution cultures required at least three signals: antigen stimulation, interleukin-2 (IL-2), and a differentiation factor distinct from IL-2. Antigen-specific CTLp proliferated in response to antigen stimulation and recombinant DNA-derived IL-2, but often failed to acquire cytolytic activity unless conditioned medium (CM) from mitogen-stimulated peripheral blood mononuclear cell (PBMC) cultures was added to the cultures. Temporal analysis of the requirement for CM indicated that it was providing a late signal for CTLp differentiation. This analysis was confirmed by developing CTLp cell lines, which were found to proliferate in response to IL-2 and antigen but not to exhibit influenza virus-specific cytotoxicity until CM was added. [ABSTRACT FROM AUTHOR]

In this report the antigen and restriction specificity of human T-cell clones induced with Dermatophagoides farinae (D.farinae) and isolated from an atopic individual with perennial rhinitis has been investigated. Of the six clones analysed, four were species specific and two showed cross- reactivity for the closely related Dermatophagoides pteronyssinus ((D. pteronyssinus). Inhibition of antigen-dependent proliferation by murine monoclonal antibodies directed against HLA-D-region gene products revealed that all the clones were restricted by HLA-DR molecules. The restriction specificity was investigated further using a panel of histocompatible and allogeneic-presenting cells. Of the clones tested, one appeared to be DR5 restricted while the remainder showed complex patterns suggesting that DRw52 and DRw53 supertypic specificities may be the restriction elements presenting antigen. [ABSTRACT FROM AUTHOR]

T-cell differentiation is known to take place in the thymus, but the precise mechanisms involved remain unresolved. In order to analyse the role of the thymic microenvironment in thymocyte maturation and generation of the T-cell repertoire, we have raised monoclonal antibodies (mAb) to thymic stromal cells, and with these can recognize, in the non-lymphoid component of the thymus, several antigenically distinct compartments. One mAb, MR6, binds to both the cortical epithelium and medullary macrophages/dendritic (Mϕ/DC) cells in sections of the human thymus. Recently, the molecule detected by MR6 has also been detected at low levels on the surface of T lymphocytes. We now report that this molecule has a relative molecular mass of 145,000 (p145-MR6) and that this appears to be the same for both thymic lymphocytes and stromal cells. Functional studies show that mAb MR6 inhibits both the antigen-specific and the IL-2-induced proliferative response of MHC class II-restricted cloned helper T cells and peripheral blood mononuclear cells (PBMC). These results suggest that the molecule to which mAb MR6 binds could be responsible for the inhibition of T-cell proliferation to self-antigens, and hence may be involved in tolerance induction and MHC restriction. [ABSTRACT FROM AUTHOR]

Transfusion with donor blood before transplantation can prolong the survival of renal allografts in the rat. The phenomenon is donor specific. We have investigated the effect of blood transfusion on both lymphocyte proliferation and the generation of donor-specific cytotoxic cells. In the first instance the kinetics of the proliferative responses of lymph node, spleen and thoracic duct lymph (TDL) leucocytes (harvested 7 days after transfusion of donor-specific blood, third-party allogeneic blood, syngeneic blood or no treatment) to lymph node stimulator cells were determined in a one-way mixed lymphocyte culture (MLC). Four strain combinations (LEW to DA, LEW to PVG, PVG to DA and DA to PVG) were investigated in this study. Maximal proliferation was observed at 4 days in the MLC and this was not altered by prior blood transfusion. When lymph node and TDL cells from transfused recipients were used as responders and stimulation was provided by cells from the same strain of rat as the blood donor, there was a significant depression of the MLC response compared to the response of cells harvested from untreated animals or animals given a syngeneic blood transfusion. This correlated with the behaviour of renal allografts in the same strain combinations. Lymph node and TDL cells harvested from rats that had received a third-party blood transfusion produced variable results in the MLC, ranging from a normal to a depressed response. No prolongation of allograft survival was noted in any animals pretreated with third-party blood. In contrast, when spleen cells were used as responder cells there was a donor-specific increase in the proliferative response on Day 4 in all strain combinations tested. In the second instance, specific cytotoxic activity was generated by in vitro (MLC) stimulation of lymph node or TDL, but not spleen, cell responders harvested from transfused or untreated rats. The activity of cytotoxic cells generated in MLC was quantified in a 51Cr-release assay, using Con A blast lymph node target cells prepared from animals of the same strain as the blood donor or a third-party strain. The specific cytotoxic activity generated was significantly increased when the responding cells were harvested from an animal that had received a donor-specific transfusion and then been restimulated by the blood donor in M LC. Thus donor-specific transfusion results in a reduction in the proliferative response of lymph node and TDL cells to blood donor-specific stimulators in MLC; however, it would appear to prime the recipient against the histocompatibility antigens of the blood donor and results in the enhanced generation of donor-specific cytotoxic cells after restimulation in vitro. [ABSTRACT FROM AUTHOR]

Cultured human NK cells and T cells grown in the presence of IL-2 and phytohaemagglutinin incorporate 35S sulphate into two distinct macromolecular species. The larger molecule was identified as a chondroitin-4-sulphate proteoglycan and was present in both cell-associated and secreted material. The smaller component was identified as free glycosaminoglycan and was present only in the cell-associated material. The sulphated macromolecules synthesized by NK cells were smaller than those produced by T cells. Growth in the presence of β-D-xyloside led to a decrease in proteoglycan production, together with an increase in the synthesis of free glycosaminoglycan. The latter molecule was found in the secreted as well as the cell-associated fraction. In all instances, growth of T cells was inhibited by xyloside in a dose-dependent fashion. However, growth of NK cells from &frac37; donors was stimulated at low concentrations of xyloside (0.25 and 0.5 mM). Growth of NK cells in xyloside had no effect on their lytic activity, and the 'NK-like' cytolytic capacity of cultured T cells was similarly unaffected. Both NK cells and T cells grown in xyloside at a concentration resulting in a 50% inhibition of intact proteoglycan synthesis did not show increased susceptibility to autolysis in the presence of NK-cell targets. These findings suggest that optimal production of the intact proteoglycan molecule may not be essential for NK-cell lytic function or protection of effector cells in vitro. [ABSTRACT FROM AUTHOR]