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The thoracic duct or efferent prescapular duct was cannulated in four fetal calves aged 121-259 days post-conception. The duration of lymph flow ranged from 2 to 20 days and the mean flow rates sustained over these collection periods varied from 54 to 488 ml/hr. Lymphocyte output ranged from 44 × 106 cells/hr in thoracic duct lymph from a 121-day fetus to 3.9 × 108 cells/hr in efferent prescapular lymph from a 259-day fetus. The circulating lymphocyte pool in fetal calves of about 120 and 190 days gestational age was calculated to contain, respectively, 4 × 108 cells and 2 × 1010 cells. The proportion of lymphocytes bearing surface immunoglobulin detected in fetal lymph ranged from 2.1% to 8.7%. Recirculating lymphocytes from fetal calves produced strong proliferative responses when stimulated by T-cell mitogens but responded poorly to B-cell mitogens. Fetal lymphocytes also responded to stimulation by allogeneic cells and stimulated other cells to proliferate during mixed lymphocyte culture. When stimulated with Con A, fetal lymphocytes secreted IL-2 to a degree that was indistinguishable from the secretory behaviour of lymphocytes from adult animals. The results presented in this paper show that chronic lymphatic fistulae can be established successfully in fetal calves to give access to recirculating lymphocytes. This provides a new experimental approach for studying the development of the bovine immune system. [ABSTRACT FROM AUTHOR]

The IL‐7/IL‐7R pathway plays a vital role in the immune system, especially in the inflammatory response. Monocytes/macrophages (osteoclast precursors) have been recently recognized as important participants in the osteoclastogenesis of rheumatoid arthritis (RA) patients. Here, we aimed to investigate the therapeutic potential of IL‐7/IL‐7R pathway in RA and to determine whether it could restrain osteoclastogenic functions and therefore ameliorate RA. Firstly, collagen‐induced arthritis (CIA) mice were administered with IL‐7Rα‐target antibodies to assess their therapeutic effect on arthritis. We found that blockade of the IL‐7/IL‐7R pathway protected CIA mice from bone destruction in addition to inducing inflammatory remission, by altering the RANKL/RANK/OPG ratio and consequently decreasing osteoclast formation. To explore the effect and mechanism of this pathway, bone marrow cells were induced to osteoclasts and treated with IL‐7, a STAT5 inhibitor or supernatants from T cells. The results showed that the IL‐7/IL‐7R pathway played a direct inhibitory role in osteoclast differentiation via STAT5 signalling pathway in a RANKL‐induced manner. We applied flow cytometry to analyse the effect of IL‐7 on T‐cell RANKL expression and found that IL‐7/IL‐7R pathway had an indirect role in the osteoclast differentiation process by enhancing the RANKL expression on T cells. In conclusion, the IL‐7/IL‐7R pathway exhibited a dual effect on osteoclastogenesis of CIA mice by interacting with osteoimmunology processes and could be a novel therapeutic target for autoimmune diseases such as RA. [ABSTRACT FROM AUTHOR]

Summary: Dysfunction of the immune system underlies a plethora of human diseases, requiring the development of immunomodulatory therapeutic intervention. To date, most strategies employed have been focusing on the modification of T lymphocytes, and although remarkable improvement has been obtained, results often fall short of the intended outcome. Recent cutting‐edge technologies have highlighted macrophages as potential targets for disease control. Macrophages play central roles in development, homeostasis and host defence, and their dysfunction and dysregulation have been implicated in the onset and pathogenesis of multiple disorders including cancer, neurodegeneration, autoimmunity and metabolic diseases. Recent advancements have led to a greater understanding of macrophage origin, diversity and function, in both health and disease. Over the last few years, a variety of strategies targeting macrophages have been developed and these open new therapeutic opportunities. Here, we review the progress in macrophage reprogramming in various disorders and discuss the potential implications and challenges for macrophage‐targeted approaches in human disease. [ABSTRACT FROM AUTHOR]

Bone marrow cells and thymus cells were observed in cell transfer expehments to collaborate in the production of anti-BSA antibodies. The target cells for tolerance induction either with a 'low dose' of antigen (100 µg of deaggregated BSA once a week × 5) or with a 'high dose' (a single injection of 5000 µg) were identified by the same technique. In 'low dose' tolerance, some indication was obtained that thymus-derived cells in peripheral lymphoid systems were the target cells; bone marrow-derived cells appeared not to be so susceptible, and the cells residing in thymus or bone marrow seemed to remain unimpaired, in contrast, the injection of a 'high dose' of tolerogen rendered both types of cells in spleen, thymus cells and bone marrow cells, unresponsive or hyporesponsive in parallel with one another. [ABSTRACT FROM AUTHOR]

Bone marrow-thymus cooperation experiments were carried out in lethally irradiated mice with sheep red blood cells (SRBC) as the antigen and direct plaque-forming cells (PFC) as the end point. Various parameters were altered, with the following results: (1) Above 800 rad, the response by marrow cells alone, as well as the increase due to added thymus cells, was independent of irradiation dose. (2) The response of marrow cells was greatest at high SRBC concentrations, but the co-operative effect of thymus cells was most evident at lower SRBC levels, and completely absent at high levels. (3) Increasing the number of marrow cells, without thymus, gave increasing numbers of PFC, but the dose-response curve did not suggest cell synergism. (4) Thymectomy and antithymocyte serum treatment of host or donor did not prevent the response by marrow cells alone. It was concluded that this was a true IgM response by antibody-forming precursors from the marrow, unaided by thymus-derived cells. [ABSTRACT FROM AUTHOR]

Summary: T cells must display diversity regarding both the cell state and T‐cell receptor (TCR) repertoire to provide effective immunity against pathogens; however, the generation and evolution of cellular T‐cell heterogeneity in the adaptive immune system remains unclear. In the present study, a combination of multiplex PCR and immune repertoire sequencing (IR‐seq) was used for a standardized analysis of the TCR β‐chain repertoire of CD4+ naive, CD4+ memory, CD8+ naive and CD8+ memory T cells. We showed that the T‐cell subsets could be distinguished from each another with regard to the TCR β‐chain (TCR‐β) diversity, CDR3 length distribution and TRBV usage, which could be observed both in the preselection and in the post‐selection repertoire. Moreover, the Dβ‐Jβ and Vβ‐Dβ combination patterns at the initial recombination step, template‐independent insertion of nucleotides and inter‐subset overlap were consistent between the pre‐ and post‐selection repertoires, with a remarkably positive correlation. Taken together, these results support differentiation of the CD4+ and CD8+ T‐cell subsets prior to thymic selection, and these differences survived both positive and negative selection. In conclusion, these findings provide deeper insight into the generation and evolution of TCR repertoire generation. [ABSTRACT FROM AUTHOR]

Regulatory T (Treg) cells play a key role in dampening excessive immune activation. However, antiretroviral therapy ( ART) -naive HIV-1 infection maintains the immune system in a sustained state of activation that could alter both Treg cell surface markers and functions. As Treg cell surface markers are directly linked to their functions the overall objective of this study was to determine how ART-naive HIV infection affects the phenotypic properties of Treg cells. Our data showed that in ART-naive HIV-1 infection, Treg cells are dominated by effector ( CD45 RA+ CD27− CCR7− CD62L−) and effector memory ( CD45 RA− CD27− CCR7− CD62L−) cells. In contrast Treg cells from HIV-negative individuals were mainly naive ( CD45 RA+ CD27+ CCR7+ CD62L+) and central memory ( CD45 RA− CD27+ CCR7+ CD62L+) cells. Whereas effector and effector memory Treg cells showed enhanced expression of CD39 ( P < 0·05), CD73 ( P < 0·001), HLA- DR and CD38 ( P < 0·001); naive and central memory Treg cells showed a significant reduction in the expression of these markers. Overall Treg cell frequencies within total CD4+ T cells correlated positively with plasmatic HIV-1 viral load. As increased viral load is associated with augmented CD4+ T-cell destruction; this could suggest a resistance of peripheral Treg cells to HIV-1 destruction. Hence the modulation of Treg cell phenotype and frequencies could be considered in designing immunotherapeutic strategies targeting immune system restoration during HIV-1 infection. [ABSTRACT FROM AUTHOR]

The concept of T-cell mediated suppression evolved more than 30 years ago. At that time it spawned many claims that have not stood the test of time. The rediscovery of suppression phenomena and regulatory T cells over the past 15 years created schizophrenic responses amongst immunologists. Some claimed that the new proponents of suppression were, once again, bringing immunology into disrepute, whilst others have embraced the field with great enthusiasm and novel approaches to clarification. Without faithful repetition of the “old” experiments, it is difficult to establish what was right and what was wrong. Nevertheless, immunologists must now accept that a good number of the old claims were overstated, and reflected poor scientific discipline. [ABSTRACT FROM AUTHOR]

The adaptive immune system requires a diverse T-cell repertoire to be able to respond to a wide variety of pathogens. Worryingly, the repertoire diversity declines dramatically in old age. As thymic output generates novel T cells, the conventional view holds that a decrease in this output with age is responsible for the loss in the repertoire. However, many additional factors affect the repertoire such as homeostatic turnover and antigen-dependent expansion in response to infection. Mathematical models taking a population biology perspective are important tools for understanding how the interplay between these factors affects the immune repertoire. These models suggest that thymic decline is not a major factor but rather that some combination of virus-induced proliferation and T-cell-intrinsic genetic or epigenetic changes gives rise to the oligoclonal expansions that cause the decline in T-cell diversity. We also discuss consequences for strategies to rejuvenate the immune repertoire in old age. [ABSTRACT FROM AUTHOR]

The concept of T-cell dependent regulation of immune responses has been a central tenet of immunological thinking since the delineation of the two cell system in the 1960s. Indeed T-cell dependent suppression was discovered before MHC restriction. When reviewing the data from the original wave of suppression, it is intriguing to reflect not just on the decline and fall of suppressor T cells in the 1980s, but on their equally dramatic return to respectability over the past decade. Hopefully their resurgence will be supported by solid mechanistic data that will underpin their central place in our current and future understanding of the immune system. [ABSTRACT FROM AUTHOR]

Naive T cells have long been thought to recirculate exclusively between secondary lymphoid organs via the lymph and blood. Evidence is now emerging that this view may be too simplistic and that naive T cells routinely traffic through non-lymphoid organs in a manner similar to that of memory T cells, albeit in lower numbers. This represents a fundamental shift in the current paradigm of T-cell migration through different types of tissue. This review summarizes these recent findings, along with the similarities and differences in migratory properties of naive and memory T cells, and discusses how and why naive T cells might access non-lymphoid tissues. [ABSTRACT FROM AUTHOR]

There are reports of immaturity of the neonatal immune system, which may explain the low incidence of graft-versus-host-disease (GVHD) after cord blood transplantation. The CD40 ligand (CD40L)–CD40 interaction is important in regulating the cellular immune response. We hypothesized that the neonatal immune system may show immaturity in this interaction. We studied the function of the CD40L–CD40 interaction in the T-cell interaction with B cells and monocytes in cord blood compared with adult blood in vitro. Consistent with previous reports, CD4+ T cells do not express CD40L after T-cell activation. In whole blood, adult monocytes, but not neonatal monocytes, were activated following T-cell activation. However, the activation of adult monocytes was not dependent on the CD40L–CD40 interaction. Using the CD40L trimer (Lt), we showed that cord B cells have comparable responses to CD40 ligation to those of the adult B cells. Both cord and adult monocytes do not respond as well as B cells and this is probably related to low density of expression of CD40. However, interferon-γ up-regulated CD40 on adult monocytes but not on cord monocytes. This potentiated the adult monocyte response to CD40 ligation by CD40Lt. Our findings suggest that the neonatal CD40L–CD40 pair is immature in the cellular immune response involving monocytes and that interferon-γ fails to activate neonatal monocytes for a response to CD40L. These findings suggest that in the inflammatory microenvironment of cord blood transplantation neonatal monocytes may play a minor role in the effector arm of the immune response. This finding may be one of several mechanisms for the low incidence of GVHD that is observed following cord blood transplantation. Also the ligand-receptor immaturity may contribute to the increased susceptibility of newborns to certain infections. [ABSTRACT FROM AUTHOR]

The distribution of T lymphocytes expressing the different polypeptides of the leucocyte common antigen (LCA) family detected by CD45R and UCHL1 antibodies has been studied in normal lymphoid tissues. In the thymus most cortical thymocytes express UCHL1 and co-express CD4 and CD8. The more mature membrane CD3+ (mainly medullary) T cells are heterogeneous and may express both UCHL1 and CD45R weakly or be restricted to display CD45R or UCHLI alone. In the medulla both the CD45R+ and UCHL1+ subpopulations contain single positive CD4 and CDS cells. In tonsils, germinal centre T cells are almost exclusively UCHL1+, CD4+ and a proportion also express HNK-l (Leu 7) antigen. In the paracortical areas approximately equal numbers of CD45R+ and UCHL1+ cells are found but these separately occupy nests of cells containing one or the other type. Again, both CD45R+ and UCHL1+ cells include single CD4+ and CD8+ lymphocytes. A small proportion (<5%) of strongly CD45R+, UCHL1+ double-stained cells are also seen, and these probably represent recently activated lymphocytes. In the gut, small clusters of such strongly double- labelled cells are in the submuscular mucosae while cells of the lamina propria are almost exclusively UCHL1+. Many intra-epithelial lymphocytes are only weakly positive or negative for UCHL l and appear to be CD45R+ . These results are consistent with the view that expression of different CD45 polypeptides identifies successive stages of thymocyte-T-cell maturation and that following their thymic education, unprimed T lymphocytes are CD45R+, while primed memory T cells arc UCHL1+. These populations occupy different microenvironments. [ABSTRACT FROM AUTHOR]

The MT-2, derived from an adult T-cell leukaemia (ATL) cell, the Molt-4F, a human T-cell line, and the Isk, an EB virus-transformed B-cell line, were found to have high-affinity receptors for somatostatin, a cyclic tetradecapeptide that inhibits the release of substances such as growth hormone, TSH, glucagon, insulin, secretin, gastrin and cholecystokinin. The quantity of radioactivity bound varied linearly with the number of cells, and was displaced by non-radioactive somatostatin in a concentration-dependent manner. Specific binding of 125I-somatostatin was time- and temperature-dependent and at 22° reached equilibrium within 120 min. Scatchard analysis demonstrated one class of specific-binding sites on MT-2 cells, Isk cells and Molt-4F cells that had respective densities and dissociation constants of 109pM and 0.64 nM, 102 pM and 1.1 nM, and 5.8 pM and 0.22 nM. [ABSTRACT FROM AUTHOR]

Using a cell culture system, age-associated changes in immune activities were investigated in newly developed, short-lived mouse strains. These SAM-P strains of mice (H-2k), which have a remarkably short life span (around 9 months) under conventional breeding conditions, showed an age-associated early decline in several immune functions, as compared to ordinary strains of AKR/J (H-2k) and C3H/He (H-2k) mice. Their antibody-forming capacity to T-independent antigen, DNP-Ficoll, and natural killer (NK) cell activity showed a markedly early onset of regression and a sharp decline from the level of control mice at 2 months of age. SAM-P strains of mice have a profound defect in antibody response to a T-dependent (TD) antigen, such as sheep red blood cells (SRBC), thus there was only a feeble antibody response to SRBC as early as the age of 2 months, and a negligible response at a later age. In contrast, the allo-specific cytotoxic T lymphocyte (CTL) response of the mice was as high as that of control mouse strains at 2 months of age and declined little until at least 6 months of age. The early age-related functional decline in the immune system of SAM-P mice suggests that these new inbred strains are appropriate models for investigating the age-related appearance of immune dysfunctions. [ABSTRACT FROM AUTHOR]

The distribution of the functional subsets of porcine T cells, the cytolytic/suppressor (Tc/s) and the helper/inducer (Th/i) cells was studied in cryostat sections of thymus, lymph nodes, tonsils, Peyer's patches, spleen and liver using the indirect immunoperoxidase technique. Three murine monoclonal antibodies (mAb) were used. The mAb 8/1 reacts with an antigen present on all T cells and on cells of the myeloid lineage; the antigen has not yet been characterized biochemically. The mAb 295/33 (anti- T8) binds to the porcine T8 antigen and defines the Tc/s subset, while mAb PT-4 (anti-T4) detects the porcine T4 antigen and defines the Th/i subset. Practically all thymocytes were stained by inAb 8/1. The majority of cortical thymocytes apparently co-expressed T8 and T4, whereas distinct fractions of medullary cells were labelled by either anti-T8 or anti-T4. In peripheral lymphoid organs all three mAb reacted with cells in the thymus-dependent areas and with cells scattered in the lymphoid follicles. In lymph nodes, tonsils and Peyer's patches, anti-T8 and anti-T4 each labelled approximately half of the cells stained by mAb 8/1. in the periarteriolar lymphoid sheath of the spleen, anti-T4 labelled more cells than did anti-T8. The reactivity of mAb 8/1 with the Kupffer cells of the liver demonstrated the expression of the 8/1 antigen on cells of the monocyte lineage. The T8 and T4 antigens could not be detected in acetone-fixed and paraffin-embedded sections, while the antigen recognized by mAb 8/1 remained preserved. Altogether, despite an inverted microanatomical structure of porcine lymph nodes, the frequency and distribution of T8+ and T4+ cells in thymus-dependent areas proved to be similar to those found in other species. [ABSTRACT FROM AUTHOR]

The capacity of T cells from different sites to augment IgA production by LPS-stimulated B cells has been investigated. Peyer's patch T lymphocytes activated with Con A induced up to a 20-fold increase in IgA production. The effect was isotype-specific, in that no consistent effect on IgG and a diminution of IgM synthesis were observed. Less activity was recorded in spleen and mesenteric lymph node T cells. Optimal activation of the Thy 1+ Lyt 1 +2- helper cells required the addition of splenic adherent cells and the elimination of Thy 1+ Lyt 2- suppressor cells prior to activation. T lymphocytes maintained regulatory activity for several months after expansion in medium supplemented with IL-2 and are now being cloned. We conclude that IgA production is under control of T cells sited preferentially, but not exclusively, in gut-associated lymphoid tissue, and that these T cells can augment IgA production by B lymphocytes from sites with low commitment to production of this isotype. [ABSTRACT FROM AUTHOR]

Bovine peripheral blood lymphocytes (PBL) were stimulated to proliferate in vitro by live, irradiated or freeze-thawed Trypanosoma brucei, but not by the isolated variant surface glycoprotein. The optimal dose was 105 trypanosomes per 5 × 105 lymphocytes in 0.2 ml. Maximal proliferation was at day 5. Of the 98 cattle tested, 36 were high-responders (stimulation indexes 20-104), 49 were iow or non-responders (SI 1-10) and 13 were intermediate. The responder status of individual animals did not change over a period of 1 year, nor did it alter following deliberate trypanosome infection. The stimulation was dependent on macrophage/ monocyte type accessory cells, and this co-operation did not seem to be MHC restricted. Lack of stimulation of non-responder PBL did not appear to be due to the activation of suppressor cells. Accessory cells from non-responder animals could complement PBL from responders, but accessory cells from responders could not complement non-responder PBL. Responsiveness is therefore a characteristic of lymphocytes. Analysis of the surface markers of these lymphocytes or the blast cells generated in culture showed that they were a subpopulation of T cells, possibly TH cells. Analysis of PBL from 98 animals, which had been selected for trypanoresistance or trypanosensitivity under natural tsetse fly challenge, failed to establish a correlation between resistance and level of lymphocyte stimulation by trypanosomes in vitro. [ABSTRACT FROM AUTHOR]

We have developed a simple assay for human peripheral-blood suppressor cells induced by soluble protein antigens. Suppressor cells were obtained from 6-day cultures in the presence of tetanus toxoid or PPD and were assayed in co-cultures with fresh autologous PBLs. The proliferative response in this second culture showed significant suppression varying from 50% to 90%. The suppressor cells are OKT8-positive, resistant to X irradiation and nonspecific in their function. They do not impede either the function or production of TCOF in the secondary culture but we are unable to detect a non-specific suppressor factor made by these cells. [ABSTRACT FROM AUTHOR]

Different T-cell subsets participating in immune responses were detected at a high frequency by a modified virus plaque assay (VPA). By using the modified VPA, different activated T-cell subsets generated in primary immune responses, helper and suppressor T cells participating in antibody formation, and effector T cells involved in the delayed-type hypersensitivity (DTH) reaction were enumerated directly without in vitro antigen stimulation. The frequency of detection in immune systems used was 7·5–17·7 V-PFC/103 spleen cells. Although neither helper T cells for antibody formation nor effector T cells for DTH reaction were detected as V-PFC at a high frequency by the original VPA, it was also found in secondary immune response that Lyt 1 positive, antigen-specific helper and effector T-cell subsets, and cyclophosphamide (CY)-resistant precursors were enumerated at a high frequency by the modified VPA when they received in vitro antigen stimulation, and that the proliferative stage of these cells was critical for the development of V-PFC. [ABSTRACT FROM AUTHOR]

Rat thymus and T-cell antigens were defined by using two distinct monoclonal antibodies (R-1-3B3 and R-1-12CS). R-1-3B3 antibody, when tested for its reactivity with rat lymphoid cells by immunofluorescence, labelled virtually all thymus and T cells but not B cells and bone marrow cells. The antigen defined by this R-1-3B3 antibody occurred more abundantly on medullary thymocytes and peripheral T cells than on cortical thymocytes. Immunochemical data showed that R-1-3B3 antibody recognized a single glycoprotein with a molecular weight of 67,000, which were able to interact with Lens culinaris haemagglutinin. R-1-12C5 antibody, on the other hand, reacted with all of thymus and T cells as well as with a subpopulation (approximately 20%) of bone marrow cells. In contrast to the antigen defined by R-1-3 B3, that detected by R-1-12C5 antibody existed largely on cortical thymocytes and to a much lesser extent on medullary thymocytes and peripheral T cells. R-1-12C5 antibody detected a single glycoprorein with a 95,000 molecular weight, which could also interact with Lens culinaris haemagglutinin. Based on these data described above and since both antigens defined by R-1-3B3 and R-1-12C5 antibodies were absent from rat brain tissue, we concluded that they were distinct from brain-associated thymic antigens in rats including Thy-1 and W3/13 antigen systems. [ABSTRACT FROM AUTHOR]

Inducibility of immunological tolerance to a T-dependent antigen, human serum albumin, was studied in autoimmune mice (NZB, MRL/Mp-1pr/1pr and male BXSB mice), comparing with non-autoimmune mice (BALB/c, DBA/2, MRL/Mp- +/+ and female BXSB mice). Weekly injections of increasing doses of the tolerogen into DBA/2 mice induced T-cell tolerance without the participation of suppressor cells and without affecting B cells. All of the autoimmune mice tested were refractory to the tolerogen; partial tolerance (40%-60% responsiveness) was attained in mice aged 1 month, but not in older mice. By comparison, tolerance was induced in non-autoimmune mice to a similar degree irrespective of the age of the mice. The tolerance inducibility was also examined in reciprocal bone marrow cell (BMC) transfer experiments between NZB and DBA/2 mice and also BMC transfer into B10.D2 mice. It was shown that recipients of NZB BMC were more resistant to tolerance induction than those of DBA/2 BMC, while irradiated NZB mice receiving DBA/2 BMC were susceptible. Hence, it is suggested that the tolerance-resistant nature of the NZB mice was inherent in T-cell precursors in the bone marrow and not in the host environment. Similar findings in support of this notion were also observed in BSXB mice. The significance of tolerance resistance in the development of autoimmunity is discussed. [ABSTRACT FROM AUTHOR]

Antiserum specific for hamster thymus-derived lymphocytes, prepared by immunization of rabbits with brain tissue from MHA/ssLAK hamsters, was, in the presence of guinea-pig complement, cytotoxic to hamster thymocytes > lymph node cells >spleen cells, while virtually unreactive against bone marrow cells. This antiserum markedly inhibited spleen cell response to the T cell mitogen, Concanavalin A, while the response to the B and T cell mitogen, pokeweed, was much less inhibited. These in vitro effects of the anti-hamster T cell serum were confirmed by utilizing lymphoid cells from thymectomized, lethally-irradiated, bone marrow-reconstituted hamsters. Lymph node cells from such animals were killed by the anti-T cell serum only to the same extent as bone marrow cells, while spleen cells from these animals gave a good response to pokeweed mitogen but were virtually unresponsive to Concanavalin A. Passage of hamster spleen cells over nylon wool columns yielded effluent populations highly enriched in T lymphocytes. The eluted cells were fully capable of T ceil functions, as determined by their blastogenic response to various T and B ceil mitogens in vitro and their ability to inhibit the growth of syngeneic SV40 tumours in vivo. [ABSTRACT FROM AUTHOR]

The present studies reinvestigate the role of the T cell in the development of resistance to Listeria monocytogenes. Doubly thymus-deprived adult thymectomized irradiated bone marrow-reconstituted mice (D-AT × BM) were prepared using anti-theta serum-treated bone marrow from AT × BM donors for reconstitution. The growth of the bacteria in spleens and livers of D-AT × BM was inhibited and such animals survived infection with doses which were lethal to normal mice. Since the D-AT × BM animals were T cell-depleted. as evidenced by (a) absence of theta-positive cells in their spleens; (b) inability to mount a primary humoral response to a T-dependent antigen and (c) failure to reject H-2 incompatible skin allografts, their antibacterial resistance was not due to the presence of a residual T-cell population. Further evidence of T-cell depletion in these animals was furnished by the findings that, despite their resistance to L. monocytogenes, they failed to exhibit a delayed hypersensitivity reaction to Listeria antigens, their splenocytes were unable to transfer resistance to naive hosts and they did not develop an anamnestic response upon secondary challenge. We concluded from these findings that primary antibacterial resistance to L. monocytogenes need not necessarily depend on the development of specific cell-mediated immunity although under normal circumstances these two processes develop in chronological association. The increased resistance of D-AT × B M animals is interpreted as being due to the enhancement of bactericidal activity of mononuclear phagocytes, possibly caused by the removal of a regulatory T-cell population. This population seems to be radiosensitive and spleen-seeking and requires an intact spleen to mediate its effect. [ABSTRACT FROM AUTHOR]

Thymus-derived cell populations were characterized by sedimentation velocity in the Earth's gravitational field, by adherence properties and in terms of the thymus-specific antigen RTLA. T cells, responding to mitogens, could be shown to be a subpopulation of RTLA-bearing cells and to have a relatively large volume. The size distribution of mitogen-responsive cells from different individuals showed some variation, but in general large spleen cells took up less thymidine per 106 cells than did large cells from other lymphoid organs. Upon stimulation with concanavalin A (con A)small popliteal lymph node cells took up more thymidine per 106 cells than did small thymus cells. The corresponding small cells of mesenteric lymph node and spleen took up intermediate quantities of thymidine. Thymusderived cells that were resistant to complementmediated cell kill with RTLA antiserum showed greater responsiveness to con A than did the original cell preparations. Non-adherent cells incorporated more thymidine when stimulated with phytohaemagglutinin (PHA) than when they were stimulated with con A. Lightly adherent cells were relatively more responsive to con A stimulation and firmly adherent cells were less responsive to both. The findings were discussed in terms of the density of RTLA on the membranes of T cells, in adherence and in sedimentation velocity fractionation, the relative yield of nucleated cells always exceeded the yield of PHAand con A-responsive cells. The differential separation of mitogen responsive and of co-operating cells were considered as a possible cause of this deficit. [ABSTRACT FROM AUTHOR]

Injection of neonatal Balb/c or C57B1/6 mice with (C57B1/6x Balb/c)F1 lymphoid cells leads to transient chimerism and runting, and to splenomegaly, deficient T-cell function and a gradual replacement of lymphoid organs with abnormal reticular cells. Activated MuLV can be isolated from such mice. It is proposed that either graft-versus-host or host-versus-graft allogeneic reactivity activates endogenous MuLV virus, which then causes functional and morphological abnormalities in the lymphoid organs. [ABSTRACT FROM AUTHOR]

The response of mouse spleen cells to the T cell-independent antigen dinitrophenylated polymer of flagellin (DNP-POL), has been studied using an adoptive transfer system, and compared with the response of bone marrow cells. Spleen cells showed a complex cell dose-response relationship, with a markedly discontinuous curve, for assays performed before day 9 after transfer and antigen challenge. This discontinuity could be explained by a delay in attainment of the peak response for lower cell inocula. The curve became linear on a log-log scale when spleens were harvested on days 9 and 10 post-transfer. Bone marrow cells gave a lower response than would be expected from their lymphocyte content. This response increased progressively with a delay before antigen challenge in the irradiated recipient or in tissue culture prior to cell transfer, suggesting a functional maturation in this cell population, whereas the performance of spleen cells fell off under similar circumstances. The findings were consistent with, but could not prove, the hypothesis that the immediate precursors of anti-DNP antibody-forming cells in bone marrow were high surface immunoglobulin density small lymphocytes that had arisen locally from precursors lacking detectable surface immunoglobulin, by a non-mitotic maturation. [ABSTRACT FROM AUTHOR]

Supernatants were obtained from cultures of keyhole limpet haemocyanin (KLH) primed mouse spleen cells, and also from cultures of KLH-educated, thymus-derived lymphocytes (T cells) after re-exposure of cells to the original priming antigen, KLH. These supernatants were able to facilitate the immune response of bone marrow-derived lymphocytes (B cells) to sheep erythrocytes (SRBC). Certain physical and biological properties of such supernatant activities are described. [ABSTRACT FROM AUTHOR]

The expression of the insulin-like growth factor binding protein-2 (IGFBP-2) was assayed in mononuclear cells originating from different organs of the immune system. All mononuclear cells studied did express IGFBP-2, but the expression level was found to be dependent on the cell type and origin of the cell. T cells showed a higher expression of IGFBP-2 mRNA than did B cells, and CD34+ stem cells expressed IGFBP-2 mRNA at a high level. Expression was highest in bone marrow and thymus. Stimulation of peripheral mononuclear cells resulted in a marked increase of IGFBP-2 mRNA and also intracellular IGFBP-2, as analysed by fluorescence staining. This increase parallels the increase of other known T-cell activation markers. Furthermore, the increase of intracellular IGFBP-2 seems to precede T-cell blast formation and all T cells in active phases of the cell cycle have high levels of IGFBP-2. Our results provide a basis for further investigations on the contribution of the IGF-system to the regulation of T-cell proliferation and differentiation. IGFBP-2, in particular, may have an important influence in the regulation of T-cell activation and proliferation. A 23187, calcium ionophore IGF I/II, insulin-like growth factor-I/II IGFBPs, insulin-like growth factor binding proteins PBMC, peripheral blood mononuclear cell MNC, mononuclear cell MACS, magnetic-activated cell sorting GAPDH, glycerinaldehydphosphate RT-PCR, reverse transcriptase–polymerase chain reaction. [ABSTRACT FROM AUTHOR]

Various studies have shown that the membrane ectoenzyme dipeptidyl peptidase IV (DP IV; CD26), expressed on T, natural killer (NK) and B cells in the immune system, is involved in the regulation of DNA synthesis and cytokine production. We show that the specific DP IV inhibitors Lys[Z(NO2)]-thiazolidide, Lys[Z(NO2)]-piperidide, and Lys[Z(NO2)]-pyrrolidide inhibit DNA synthesis as well as production of interleukin-2 (IL-2), IL-10, IL-12, and interferon-γ (IFN-γ) of pokeweed mitogen (PWM)-stimulated purified T cells. Most importantly, these inhibitors induce a three- to fourfold increased secretion of latent transforming growth factor-β1(TGF-β1) by PWM-stimulated peripheral blood mononuclear cells (PBMC) and T cells, as measured with a specific TGF-β1 enzyme-linked immunosorbent assay and in the Mv1Lu bioassay. As we could demonstrate previously, TGF-β1 exhibits the same inhibitory effects as DP IV inhibitors on DNA synthesis and cytokine production (Cytokine 1994, 6, 382–8; J Interferon Cytokine Res 1995, 15, 685–90). A neutralizing chicken anti-TGF-β1 antibody was capable of abolishing the DP IV inhibitor-induced suppression of DNA synthesis of PWM-stimulated PBMC and T cells. These data suggest that TGF-β1 might have key functions in the molecular action of DP IV/CD26 in regulation of DNA synthesis and cytokine production. [ABSTRACT FROM AUTHOR]

As monocytes differentiate into mature macrophages, subsets emerge that exhibit stimulatory, suppressive or phagocytic potential. These functionally distinct subsets can be discriminated using monoclonal antibodies RFD1 and RFD7. As examples of all these subsets have been repeatedly identified within the macrophage pool in a variety of organs the overall functional capacity of this pool will depend on the relative balance of these subpopulations. This study investigates whether this balance present in mature macrophage populations can be regulated by the local influence of T-cell-derived cytokines. The dose-dependent effect of cytokines interferon-γ (IFN-γ), interleukins (IL) IL-2, IL-4 and IL-10 on the phenotype and function of monocyte-derlved macrophages was determined. Subsets of mature cells were quantified by identifying RFD1+ RFD7- stimulitory cells (Dl+); RFD1- RFD7+ phagocytes (D7+) and RFD1+ RPD7+ suppressive cells (D1/D7+). IFN-γ and IL-4 increased the relative proportions of Dl+ stimulatory cells and upregulated HLA-DR expression IFN-γ also increased the capacity of the mature macrophage pool to stimulate T-cell proliferation. IL-10 reduced the proportions of Dl+ stimulatory cells while promoting the differentiation of D7+ phagocytes and D1/D7+ suppressive cells. IL-10 induced changes also reduced the functional capacity of the mature populations to stimulate T cells in auto and allogenic mixed lymphocyte reactions (MLR). IL-2 had no effect on differentiation of monocytes. Thus IL-4 and IFN-γ are seen to induce the development of stimulatory macrophages while IL-10 promotes differentiation of monocytes to mature phagocytes and suppressive macrophages. It is concluded that mature macrophage phenotype is `plastic' and under the control of T-cell-derived mediators. Furthermore, within the differentiating monocytes, phenotypic change appears to carry with it functional change, thus retaining the relationship between antigen expression and activity in the mature macrophage populations. [ABSTRACT FROM AUTHOR]

The present study describes the distribution of CD4/CD8 double-positive (DP) T cells in lymph nodes and mucosa-associated lymphoid tissues of pigs at 6–7 months of age. Proportions of lymphocytes isolated from peripheral, bronchial and mesenteric lymph nodes expressing CD4 and/ or CD8 molecules were similar and ranged from 10-13% CD4/CD8 DP cells, 25-27% CD4 single-positive (SP) cells, and 27-32% CD8 SP cells. Mucosa-associated lymphoid tissues had significantly smaller proportions of CD4+ and/or CD8+ T cells than lymph nodes and CD4/CD8 DP cells accounted for a larger proportion of the total CD4+ lymphocytes than in lymph nodes. Compared to the lymph nodes, the predominant CD4+ and/or CD8+ T-cell subset in tonsils was the CD4/CD8 DP population (18%), because of both a higher proportion of these cells and a lower proportion of CD4 SP (12%) and CD8 SP (14%) lymphocyte subsets. Jejunal Peyer's patches were comprised of 12% CD4 SP, 28% CD8 SP and 10% CD4/CD8 DP lymphocytes. In contrast, the mid-section of the continuous Peyer's patch in the ileum contained 7% CD4 SP, 8% CD8 SP and 4% CD4/CD8 DP lymphocytes. The distribution of T lymphocytes in porcine mucosal lymphoid aggregates agrees with the reported correlation between high and low rates of lymphocyte entry into these tissues and the abundance or scarcity of T cells, respectively. Defining the role of CD4/CD8 DP lymphocytes and their unique distribution in mucosa-associated lymphoid tissues in the pig may reveal novel T-cell-mediated regulatory pathways. [ABSTRACT FROM AUTHOR]

lnterleukin-6 (IL-6) has been shown to regulate numerous functions of the immune system including the differentiation of T-cell subpopulations. Here we examined the involvement of this cytokine in the in vivo generation of a population of T cells able to protect mice against mycobacterial infections. BALB/c mice were infected intravenously with Mycobacterium avium 2447 and anti-IL-6 monoclonal antibodies were administered intraperitoneally throughout the course of the infection. Control mice were able to control the mycobacterial proliferation I month after inoculation, whereas mice whose IL-6 had been blocked showed progressive bacterial growth. To distinguish a role for IL-6 associated to the induction or expression of immunity mediated by T cells, we immunized mice with M. boris bacillus Calmette-Guérin (BCG) Pasteur and challenged them 2 months later with M. avium. One group of mice received anti-IL-6 during the BCG vaccination and another during the M. avium challenge. When M. avium proliferation was assessed at day 30 of the challenge, it was found that the administration of anti-IL-6 during vaccination reduced the protection afforded by BCG compared to administration of the isotype control antibody. No difference in bacterial proliferation was observed at day 30 of challenge when antibodies were administered during M. avium challenge. Our results show that protective T cells arise during M. avium infections in mice after differentiating in the presence of IL-6. [ABSTRACT FROM AUTHOR]

A 180,000 MW molecule has been identified on porcine leucocytes that is the homologue of the 215,000/300,000 MW WC1 (T19) leucocyte antigen previously considered to be restricted to ruminants. In ruminants the WC1 molecule is expressed by a T-cell subpopulation that is CD2-CD4-CD8-CD5+ and that is γδ T-cell receptor positive (TcR+). In pigs, the 180,000 MW molecule, identified by a new monoclonal antibody CC101, is expressed by a γδ TcR+ T-cell subpopulation that is also CD2-CD4 CD8. The p180+ cells are a major T-cell subpopulation comprising approximately 40% of the peripheral blood mononuclear cells from 6-9-month-old pigs. Expression of p180 identifies the majority of the CD2-CD4-CD8- T cells in porcine blood. The p180+ T cells have a distribution in lymphoid tissues that is distinct from that oft cells that express the CD2, CD4 or CD8 molecules. They are evident particularly in the thymic medulla, the epithelium, lamina propria and interfollicular areas of the small intestine, and the superficial dermis of the skin, but largely absent from conventional T-dependent areas of secondary lymphoid tissue. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) has recently been identified as a potent and pleiotropic intracellular mediator produced by and acting on many cells of the body. Although considerable attention has been devoted to the regulation of NO by inflammatory cytokines, and also to the role of NO as an important effector molecule in immune function, there is very little information on the role of this mediator in modulating T-cell-dependent cytokine production. In this study we show that physiological levels of NO (either produced by activated macrophages or by the addition of exogenous NO donors) can selectively down-regulate interleukin-3 (IL-3) production by spleen cells from contact-sensitized mice, while leaving IL-2 activity unaffected. Thus NO may have an important role as an immunomodulatory as well as effector molecule in the immune system. [ABSTRACT FROM AUTHOR]

Interferon-γ (IFN-γ) is an important cytokine which regulates inflammatory and immune response mechanisms. IFN-γ enhances the presentation and recognition of antigens by inducing the expression of major histocompatibility complex (MHC) proteins, by activating effector T cells and mononuclear phagocytes, and by modulating immunoglobulin production and class selection in B cells. Inappropriate production of IFN-γ has been implicated in the pathogenesis of several autoimmune and inflammatory diseases and in graft rejection. Here, we describe, a recombinant inhibitor of IFN-γ, termed murine IFN-γ receptor immunoadhesin (mIFN-γR-IgG). We constructed this immunoadhesin by linking the extracellular portion of the mouse IFN-γR to the hinge and Fc region of an IgG1 heavy chain. Murine IFN-γR-IgG is secreted by transfected cells as a disulphide-bonded homodimer which binds IFN-γ bivalently, with high affinity and in a species-specific manner. In vitro, mIFN-γRIgG can block mIFN-γ-induced antiviral activity and expression of the class I MHC antigen H-2Kk in cultured cells. In vivo, mIFN-γ,R-IgG can block the function of endogenous mIFN-γ in mouse models of infection with Listeria monocytogenes and of contact sensitivity. These results show that mIFNγR-IgG is an effective and specific inhibitor of mIFN-γ both in vitro and in vivo. Thus, in general, IFN-γ receptor immunoadhesins may be useful for investigating the biological functions of IFN-γ as well as for preventing deleterious effects of IFN-γ in human disease. [ABSTRACT FROM AUTHOR]

The present report shows the capacity of hypothalamic extract (HE) to differentiate bone marrow cells to Thy-1+ cells in vitro. A two-step short-term culture was used. In the first step thymus and pituitary were co-cultured in the presence of HE. Supernatant was then transferred to a bone marrow cell suspension and following a period of culture. The percentage of Thy-1+ cells was determined by a microcytotoxicity assay. Results indicated that: (a) HE from young mice show a very efficient differentiating capacity; (b) HE from young mice is equally efficient when old pituitary, thymus and marrow are used; (c) HE from old donors has no capacity to differentiate T cells; (d) there is a progressive age-related decline of this capacity; and (e) there is a feed-back mechanism involved in this process. It is concluded that hypothalamic factors can regulate the differentiation of T cells and that this effect operates through a mechanism involving pituitary and thymus. [ABSTRACT FROM AUTHOR]

A micro-immune adherence assay employing direct microscopic observation was used to detect the presence of thymus-derived cell antigenic specificities on guinea-pig lymph node cells, purified peritoneal exudate lymphocytes, and thymocytes using a heterologous burro anti-guinea-pig thyrnocyte serum. A method is described for the direct determination of thymus-derived cell specificity of anti-lymphocyte sera. [ABSTRACT FROM AUTHOR]