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Previous work from this laboratory has shown that preimmunization of syngeneic hosts with Rous sarcoma virus (RSV)-transformed cells elicits a strong immune response against the growth of transplantable RSV sarcomas, mediated by T lymphocytes expressing the surface phenotype of helper cell precursors (Prat, Di Renzo & Comoglio, 1983). This paper shows that anti-tumour immunity may be elicited in tumour-bearing animals by triggering an experimentally pre-amplified T-helper cell population at the site of tumour growth. Mice were treated with cyclophosphamide (which inactivates suppressor T cells) followed by skin sensitization to trinitrochlorobenzene (TNCB) according to a protocol that has been shown to induce an appreciably amplified generation of trinitrophenyl (TNP)-reactive helper T cells (Fujiwara et al., 1984). Five weeks after TNCB painting, mice were transplanted s.c. with a lethal dose of RSV-induced syngeneic sarcoma cells; the injection at the tumour site of TNCB induced the regression of the tumour in mice in which the TNP-helper cell population has been amplified, but not in controls, including those injected with a non-related hapten or sensitized to TNCB without inactivation of suppressors. [ABSTRACT FROM AUTHOR]

This paper investigates desensitization in vitro, e.g. the inhibition of the transfer of contact sensitivity to picryl chloride by incubation of the passive transfer population with picrylated spleen cells. It asks whether desensitization is based on the same T-suppressor circuit which is responsible for the inhibition of passive transfer by antigen-specific T-suppressor factor (TsF). In this circuit, the T-suppressor cell which acts at the efferent stage (Ts-eff) makes TsF. This TsF depresses contact sensitivity indirectly by arming a T-acceptor cell (Tacc). The armed Tacc, when exposed to antigen (picrylated spleen cells), liberates a non-specific inhibitor which blocks the transfer of contact sensitivity. The three elements of this T-suppressor circuit occur in nylon wool-purified T cells prepared from the lymph nodes and spleens of mice four days after immunization with picryl chloride. This population transfers contact sensitivity and can be desensitized in vitro. It contains Ts-eff which can be isolated by panning (adherence) on picrylated albumin and detected by their ability to inhibit passive transfer. The 24 hr supernatant of cultures of these cells contains TsF. Finally the population contains Tacc which appear in the spleen 2 days after immunization and virtually disappear by 10 days. Further experiments demonstrated that the Ts-eff and the Tacc were not merely present but actually required for desensitization in vitro. Immune cells depleted of both Ts-eff (by panning on picrylated albumin) and Tacc (by arming with anti-oxazolone TsF and panning on oxazolonated albumin) cannot be desensitized. To restore desensitization both Ts-eff and Tacc must be added back. The Ts-eff were characterized as cyclophosphamide resistant, adult thymectomy sensitive cells (Cyr, ATx5), which adhered to antigen and were produced only by specific immunization. The Tacc were characterized as CF5, ATx5 cells which adhered to antigen only after arming with antigen-specific T-suppressor factor and were produced after immunization with an unrelated contact sensitizer, 'oxazolone'. It was concluded that desensitization in vitro was due to the interaction of two distinct T cells: the T-suppressor cell which acts at the efferent stage of the contact sensitivity reaction and the T-acceptor cell which becomes armed with the specific T-suppressor factor produced by the Ts-eff. [ABSTRACT FROM AUTHOR]

Peripheral lung tissue contains large numbers of T cells, strategically located for immune surveillance at the blood-air interface. Given the intensity of antigenic exposure at this site, it is clear that local T-cell activation events require strict control, in order to maintain tissue homeostasis. How this control is achieved in this unique tissue microenvironment is unknown, and the present study sought to elucidate the process via detailed analysis of the surface phenotypic characteristics of freshly isolated lung T cells. We report below that these cells display typical characteristic of ‘postactivation’, notably elevated basal Ca2+ concentrations, down-modulated T-cell receptors, expression of Ia and ‘late’ activation antigens and concomitant CD4/CD8. However, levels of interleukin-2 receptor and CD2 expression were below those expected of ‘activated’ T-cell populations, and virtually all of the cells were found to be in the G0/G1 phases of the cell cycle. These properties bear a remarkable similarity to those of T cells activated in the presence of endogenous tissue (alveolar) macrophages from the lung (see accompanying paper). We hypothesize that they reflect the in vivo operation of an endogenous macrophage-mediated T-cell anergy-induction process, the function of which is to limit the local clonal expansion of T cells in peripheral lung tissue after in situ activation. [ABSTRACT FROM AUTHOR]

Hepcidin regulates intracellular iron levels by interacting with and promoting the degradation of ferroportin, a membrane protein and the only known cellular iron exporter. Studies of hepcidin expression and regulation have focused on its effects in innate immunity and as a regulator of systemic iron metabolism. In the present study we characterized the expression of hepcidin messenger RNA (mRNA) in human peripheral blood mononuclear cells (PBMCs) with a focus on peripheral blood lymphocytes (PBLs). We found that (1) all human PBMCs analyzed express basal hepcidin mRNA levels; (2) hepcidin mRNA expression increases after T-lymphocyte activation; (3) expression by PBLs increases in response to challenge by holotransferrin (Fe-TF) and by ferric citrate in vitro; (4) the Fe-TF-mediated up-regulation of hepcidin decreases ferroportin expression at the cytoplasmic membrane of PBLs; and (5) silencing of tumour necrosis factor-α (TNF-α) abrogates the effect of Fe-TF. In summary, we show that hepcidin expression determines intracellular iron levels by regulating the expression of ferroportin, as described in other cells, and that inappropriately low expression of hepcidin impairs normal lymphocyte proliferation. The results establish hepcidin as a new player in lymphocyte biology. [ABSTRACT FROM AUTHOR]

X-irradiated (250 rads) A mice injected with syngeneic trinitrophenylated spleen cells (Syn-TNP-SC) developed syngeneic delayed-type hypersensitivity (Syn-DTH) after footpad challenge with syngeneic concanavalin A-induced lymphoblasts (Syn-Con A blasts), as indicated by footpad swelling and lymph-node proliferation assays. Genetic analysis with different recombinant strains of mouse revealed that the H-2Dd subregion restricts these immunological activities. A small immunogenic entity was isolated from Syn-TNP-SC extract by gel filtration and affinity chromatography with anti-Dd antibody. X-irradiated A mice injected with this antigen also generated inflammatory responses after challenge with Syn-Con A blasts. Analysis of the data obtained from the gel filtration and the affinity chromatography suggest that the Syn-DTH-stimulating antigen is a fragment of the H-Dd heavy chain with a molecular weight (MW) of 5,000 to 10,000. This fragment does not contain TNP molecules or sugar moieties and neither does it express affinity for antibodies against class 11 products. Ltk- cells transfected with the H-2Dd gene also induced Syn-DTH in X-irradiated A mice, while the parent cells failed to stimulate such a response. Taken together these findings indicate that the selection process in the thymus is not absolute and T cells recognizing self-major histocompatibility complex (MHC) products do migrate from this organ to the periphery of the immune system. The possible biological significance of these autoreactive cells is discussed. [ABSTRACT FROM AUTHOR]

The mechanism by which a Db-specific helper clone (clone 9) and a hybridoma-derived Db-especific helper factor, referred to as ASHF, induced cytotoxic T lymphocyte (CTL) responses to alloantigens was investigated. Clone 9 or ASHF helped CBA thymocytes to produce CTL against B6 (H-2b), but not D2 (H-2d), alloantigens. However, when BDF1 (H-b,d) spleen cells or an equal mixture of B6 or D2 spleen cells were used as stimulator cells, CTL responses to both B6 and D2 were induced. This suggested that clone 9 cells or ASHF could induce the production of long-ranged, non-antigen-specific helper factor(s) in B6-stimulated cultures. One of these long-ranged factors produced in B6-stimulated cultures was found to be interleukin-2 (IL-2). Thus, clone 9, which is a non-IL-2 producer, increased the production of IL-2 by irradiated B6 spleen cells and by CBA anti-B6 cultures by 4·7- and 5·7-fold, respectively. ASHF did not increase the amount of IL-2 produced by irradiated B6 spleen cells but increased the amount of IL-2 produced in CBA anti-B6 cultures by 3·8-fold. Clone 9 cells or ASHF did not increase IL-2 production in D2-stimulated cultures. Upon stimulation with concanavalin A or antigen, clone 9 cells also produced a non-antigen-specific helper factor. This factor (IL-X) synergized with excess human recombinant IL.2 (rIL-2) in the polyclonal activation of BDF1 or D2 CTL precursors. A model that involves the participation of ASHF, clone 9 cells, IL-2 and IL-X in the induction of a cytotoxic response is proposed. [ABSTRACT FROM AUTHOR]

From our experiments and those of others in which cells were cultured at a density of 100,000 cells per well, it has been suggested that auto antibody production against mouse bromelain-treated erythrocytes (mouse brom-RBC) was independent of T cells, and further, was enhanced by the removal of T cells from responsive cell populations. Here it is shown in limiting dilution cultures that the autoimmune response is highly dependent on T cells or their products. B cells purified from the peritoneal cavities of untreated mice did not differentiate in vitro into autoantibody-secreting cells unless provided with signals from at least one of two types of accessory cells. These were plastic adherent cells and T cells, derived either from the peritoneal cavity or from established cell lines. Here it is shown that peritoneal T cells or T cells from the LBRM-33 cell line stimulated the differentiation of purified B cells in vitro in the absence of added mitogens. The accessory cell effect could be transferred in supernatants derived from T-cell cultures but not filler-cell cultures. Recombinant interleukin-2 (rIL-2) added to culture medium did not stimulate B cells directly, but could increase precursor frequencies when added to unfractionated peritoneal cell cultures, or B-cell cultures to which cells from a T-cell line had been added. From these results, it is concluded that the differentiation of precommitted peritoneal B cells in vitro into autoantibody secretors is at least partially dependent on T cells or lymphokines derived from them. Therefore, any proposed mechanisms for regulation of this autoimmune response should encompass the requirement for T cells or their products in the final differentiation stages to autoantibody secretion. [ABSTRACT FROM AUTHOR]

PPD-reactive T cell clones have been used to analyse the nature of T lymphocytes that are involved in the 'heterogenization' of turnout cells. This is a phenomenon where coupling turnout cells to a strong antigen (in this case PPD) causes an enhanced immune response to tumour-specific antigens to be elicited providing that the host shows T cell immunity to the strong antigen (in this case is BCG positive). Clones of T cells with the Lyt1+ 2- phenotype which were unable to mediate delayed-type hypersensitivity but which provided efficient help to hapten-primed B cells were found to potentiate anti-turnout immunity in BCG-negative syngeneic mice when immunized with Con-A-PPD coupled, X-irradiated MC6A tumour cells. There therefore appears to be a mechanism whereby a helper T cell response to one antigen can provide help for the generation of a T cell response to a linked antigen which is analogous to the well-known phenomenon of help to hapten primed B cells. Furthermore the clones of T cells that help B cells the best are those that give maximal augmentation of T cell immunity. [ABSTRACT FROM AUTHOR]

Inclusion of 14% Ficoll in the assay of rosette formation of human lymphocytes with mouse red blood cells (RBC) markedly enhances the cellular interaction. Both the strength of the rosettes (number of attached RBC) and the number of reacting lymphocytes are increased significantly, irrespective of the lymphocyte source—blood, lymph node and tonsil. In the presence of Ficoll, most of the sIg-bearing B lymphocytes [expressing receptors for Fc(IgG) and/or C3] and a significant number of the sheep RBC-rosetting T lymphocytes (particularly the nylon wool non-adherent subset from the tonsil), express receptors for the mouse erythrocyte. [ABSTRACT FROM AUTHOR]

The role of mononuclear phagocyte system (MPS) in the induction of suppressor T cells which depress the delayed footpad reaction to sheep erythrocytes (SR BC) was studied in mice in which MPS was blocked or stimulated. Colloidal carbon and diethyl- stilbestrol were used for blockade and stimulation respectively. Adoptive transfer of suppressor T cells was achieved by spleen cells of mice immunized intra- peritoneally with varying doses of SRBC. In non-treated mice, 1 × 109 SRBC were required to induce suppressor T cells, while 6 × 108 could not induce the suppressor T cells. In MPS-blocked mice, however, even 6 × 108 SRBC could induce the suppressor T cells. On the other hand, 3 × 108 SRBC were required for the induction of suppressor T cells in MPS-stimulated mice. These results suggest that the activity of macrophages as scavenger cells modulates the subsequent induction of suppressor T cells after immunization with high doses of SRBC. [ABSTRACT FROM AUTHOR]

Nude and normal CBA mice have been used in adoptive transfer experiments to analyse the development of immunological memory. The development of B-cell memory to xenogeneic erythrocyte antigens is to a very large degree dependent on the presence of T cells, wit h IgG memory being somewhat more dependent than IgM memory. In this system, the expression of B memory, that is the transformation of memory cells to antibody-secreting cells under the inductive influence of antigen, is largely dependent on the presence of T cells. Primed (educated) T cells can have an antigen-specific potentiating effect on unprimed B cells in the presence of antigen. [ABSTRACT FROM AUTHOR]

The mouse Nrampl (Bcg) gene on chromosome 1 exerts pleiotropk effects on macrophage function. The gene is known to affect presentation of mycobacteria, and other antigens in vitro, so that macrophages carrying the resistant Bcg allele better support the proliferation of antigen-specific T cells compared with macrophages of the sensitive phenotype. To determine whether the Bcg allele could affect in vivo the antibody response to antigens not related to mycobacterial infections, we tested the primary and secondary responses to sheep red blood cells (SRBC) and glycosylated bovine insulin (G-insulin) in two pairs of Bcg congenic strains: BALB/c (Bcgs) versus BALB/c.CD2 (Bcgr), and B10.A (Bcgs) versus B10Ar (Bcgr), and in C57BL/10ScSn (B10; Bcgs) and A/J (Bcgr) mict. Furthermore, the antigen-specific proliferative responses of T cells primed in vivo by protein antigens were also tested in Bcg congenic mice. We found no significant difference in vim antibody response either to SRBC or G-insulin between the Bcgr and Bcgs strains. The magnitude of in vitro antigen-specific proliferation of lymph node cells sensitized in vivo by hen egg lysozyme (HEL) or chicken ovalbumin (OVA) was also similar in Bcgs and Bcgr congenic mice. However, we have documented a higher antigen-presenting capacity of Bcgr macrophages in vitro antigen-specific proliferation to OVA. Since the macrophages are the only cells in which the Nrampl gene is expressed, we suggest that the activity of other types of antigen-presenting cells masks the effect of the Bcgr allele on antigen-presentation in vivo. [ABSTRACT FROM AUTHOR]

In this study, we examined the ability of varying populations of donor cells from B6 mice to induce hyporesponsiveness in T lymphocytes from C3H mice in vitro and in vivo. Small, resting B lymphocytes were inefficient stimulators of T-lymphocyte proliferation compared to splenic mononuclear cells (SMNC) and lipopolysaccharide (LPS)-induced B-cell blasts in vitro (P < 0.05). Pretreatment of SMNC with anti-B7-1 or anti-intracellular adhesion molecule-1 (ICAM-1) monoclonal antibodies (mAb) similarly resulted in inefficient stimulation of T-cell proliferation in vitro (P < 0.05). However, in vivo, only intrahepatic, but not intravenous, injection of donor cells into C3H mice resulted in decreased T-lymphocyte proliferation in response to restimulation by alloantigen. This effect was most pronounced following intrahepatic injection of resting B lymphocytes or SMNC pretreated with anti-ICAM-1 mAb compared to uninjected or intravenously injected mice (P < 0.05). The hyporesponsiveness was associated with an increased production of interleukin-4 (IL-4) by the responder T lymphocytes and correlated with enhanced skin allograft survival. These data demonstrate that intrahepatic injection of donor-derived cells induces T-lymphocyte hyporesponsiveness. The mechanism appears to be modulated by an ICAM-1-mediated signal resulting in expansion of an IL-4-producing T-lymphocyte population. [ABSTRACT FROM AUTHOR]

In this study the involvement of peripheral γδ T cells, prepared by flow cytometry, in the immune response of cattle to primary infection with Trypanosoma congolense was assessed. Negligible in vitro proliferative responses were observed in γδ T cells isolated from trypanosusceptible Boran (Bos indicus) cattle at all stages examined post-infection when stimulated in vitro with parasite antigens. In contrast, both CD8+ T cells and γδ T cells from trypanotolerant N'Dama (Bos taurus) cattle proliferated markedly when stimulated in vitro with a complex of invariant trypanosome antigens with MW between 100 000 and 140 000 (100 000 MW complex). Neither species of cattle exhibited significant T-cell recognition of trypanosome variable surface glycoprotein (VSG). To study further the functional and phenotypic characteristics of the γδ T-cell response, four T-cell lines were established from infected N'Dama cattle. These cell lines were comprised of up to 96% γδ (WC1+) T cells, the remainder being CD8+ T cells. Two of these γδ T-cell lines exhibited 100 000 MW complex antigen specificity which was not major histocompatibility complex (MHC) restricted in one line. [ABSTRACT FROM AUTHOR]

BoCD4+T-cell clones specific for a peptide derived from foot-and-month disease virus envelope protein, VP1 (FMDV15) were generated from two responder cattle. One animal was a high and the other was an intermediate responder in terms of both T-cell and antibody responses. However both animals had identical major histocompatibility complex (MHC) class II DR-like types (DRBF3,6) according to a one-dimensional isoelectric focusing method which distinguishes DR-like alleles. In contrast, mixed lymphocyte reaction (MLR) responses indicated that they shared only one haplotype (DRBF3) and anti-DRBF6 alloclones also differentiated between the animals. This suggested that the animals differed at a non-DR-like locus. Restriction patterns of FMDV-specific clones derived from these animals indicated that FMDV15 was presented by the non-DR-like class II molecules associated with DRBF6. Only one clone, derived from the high responder animal, was restricted to DRBF3. Thus products from the non-DR-like locus (probably DQ-like) are functionally important for presentation of FMDV peptides. Furthermore the allelic differences detected by the alloclones are also critical for peptide binding. The majority of clones from the high responder animal recognized an immunodominant region containing a Rothbard epitope whereas none of the clones from the intermediate responder did so. This suggests that the region recognized by T cells, which is dependent upon MHC type, influences the B-cell response and thus the degree of protection obtained. This has major implications for rational vaccine design involving T- and B-cell epitopes. [ABSTRACT FROM AUTHOR]

During primary tsetse-transmitted challenge of Boran (Bos indicus) cattle with Trypanosoma congolense ILNat 3.1, a transient parasite antigen-specific T-cell proliferative response was observed in peripheral blood mononuclear cells and splenic mononuclear cells stimulated in vitro. A response was also observed with cells of N'Dama (Bos taurus) cattle, but in this case higher stimulation indices were observed and the response was maintained until the termination of the experiment at 40 days post-infection (p.i.). The highest parasite antigen-specific proliferative responses were observed at 20 days post-infection. At this time N'Dama cattle not only responded to the antigens derived from the infecting clone (ILNat 3.1), but also to antigens from a clone of a different serodeme (ILNaR 2), whereas Boran cattle only recognized antigens from the infecting clone of parasites. To determine the molecular mass of the antigenic trypanosome proteins, whole trypanosome lysates made from T. congolense ILNat 3.1 were fractionated by SDS-PAGE and transferred onto nitrocellulose membranes. The major protein bands were isolated and used directly in T-cell proliferation assays, In this instance, no differences in the antigen recognition profiles of Boran and N'Dama cattle were observed. The variable surface glycoprotein did not induce T-cell proliferation in infected cattle despite the presence of serum antibodies to this variable antigenic type. [ABSTRACT FROM AUTHOR]