Deep sequencing of the TCR-ß repertoire of human forkhead box protein 3 (FoxP3)+ and FoxP3- T cells suggests that they are completely distinct and non-overlapping.

Maintenance of peripheral tolerance requires a balance between autoreactive conventional T cells (Tconv ) and thymically derived forkhead box protein 3 (FoxP3)+ regulatory T cells (tTregs ). Considerable controversy exists regarding the similarities/differences in T cell receptor (TCR) repertoires expressed by Tconv and tTregs . We generated highly purified populations of human adult and cord blood Tconv and tTregs based on the differential expression of CD25 and CD127. The purity of the sorted populations was validated by intracellular staining for FoxP3 and Helios. We also purified an overlap group of CD4 T cells from adult donors to ensure that considerable numbers of shared clonotypes could be detected when present. We used deep sequencing of entire TCR-ß CDR3 sequences to analyse the TCR repertoire of Tconv and tTregs . Our studies suggest that both neonatal and adult human Tconv and tTreg cells are, in fact, entirely distinct CD4 T cell lineages.

The histocompatibility restrictions on macrophage T-helper cell interaction determine the histocompatibility restrictions on T-helper cell B-cell interaction.

To study the histocompatibility restriction between macrophages and helper T cells, carrier primed guinea pig T cells were positively selected in vitro with antigenpulsed macrophages for 7 days and the selected T cells were then mixed with hapten-primed B cells and stimulated with antigen in a modified Mishell-Dutton system. Helper T cells could only be selected with syngeneic, but not allogeneic, antigen-pulsed macrophages and would then collaborate only with syngeneic, but not allogeneic, hapten-primed spleen cells. When F1 T cells were selected with antigen-pulsed parental macrophages they would only collaborate with B cells of the same parental strain as the macrophages used in the selection culture. These results are strongly in support of the view that the primed T cell is activated by carrier determinants of the nominal antigen in association with Ia antigens on macrophages and the helper T cell, in turn, activates B cells which bear the same Ia antigens and determinants of the nominal antigen bound to immunoglobulin receptors on their surface. In addition, in experiments with antigens the response to which is controlled by I-linked genes, we demonstrated that primed (responder X nonresponder)F1 T cells would only collaborate with B cells of the responder parent. The defect appeared to be at the level of the B cell in that the addition to the cultures of antigen-presenting cells of the responder type did not restore the ability of F1 T cells to collaborate with non-responder B cells.

Monoclonal antibodies to guinea pig Ia antigens. II. Effect on alloantigen-, antigen-, and mitogen-induced T lymphocyte proliferation in vitro.

Four xenographic monoclonal antibodies to guinea pig Ia antigens were tested for their inhibitory effects on antigen-, alloantigen-, and mitogen-induced T cell proliferation. All four monoclonal antibodies reacted with strain 2 Ia antigens, and all four were capable of inhibiting the strain 13 against strain 2 mixed leukocyte reaction (MLR) by 50-70%; the two monoclonals that reacted with strain 13 Ia antigens were also capable of inhibiting the strain 2 against strain 13 MLR. In contrast, an analysis of the effects of a single monoclonal antibody on the responses to several antigens demonstrated a selective monoclonal pattern of inhibition in that the responses to some, but not all, antigens were inhibited. These results suggest that monoclonal antibodies react with different parts of Ia molecules that may have different functional roles and that certain parts of an Ia molecule participate in the presentation of certain antigens, whereas other regions of the same molecule present different antigens.

Antigen-presenting cells from nonresponder strain 2 guinea pigs are fully competent to present bovine insulin B chain to responder strain 13 T cells. Evidence against a determinant selection model and in favor of a clonal deletion model of immune response gene function.

To test directly the determinant selection hypothesis of immune response gene function, we primed strain 13 T lymphocytes in vitro with allogeneic bovine insulin pulsed strain 2 macrophages. Strain 2 macrophages were found to be fully competent to present bovine insulin B chain to strain 13 T cells despite the fact that strain 2 guinea pigs are normally totally unresponsive to this antigen. These results are incompatible with a strict interpretation of the determinant selection hypothesis, which would have predicted that strain 2 macrophages would have been restricted to the presentation of A chain loop determinants. In addition, a comparison of the reactivity profiles of self-Ia- and allo-Ia-restricted strain 13 T cells to a series of synthetic B chain peptide fragments revealed that the allo-Ia-restricted populations could be activated by autologous guinea pig insulin. Taken together, these observations strongly suggest that the clonal deletion of self-reactive cells is likely to be I region restricted and that nonresponsiveness to any protein antigen may result from a restriction in the T cell repertoire that is generated during ontogeny by a clonal deletion mechanism of tolerance to self.

CD4+CD25+ immunoregulatory T cells suppress polyclonal T cell activation in vitro by inhibiting interleukin 2 production.

Peripheral tolerance may be maintained by a population of regulatory/suppressor T cells that prevent the activation of autoreactive T cells recognizing tissue-specific antigens. We have previously shown that CD4+CD25+ T cells represent a unique population of suppressor T cells that can prevent both the initiation of organ-specific autoimmune disease after day 3 thymectomy and the effector function of cloned autoantigen-specific CD4+ T cells. To analyze the mechanism of action of these cells, we established an in vitro model system that mimics the function of these cells in vivo. Purified CD4+CD25+ cells failed to proliferate after stimulation with interleukin (IL)-2 alone or stimulation through the T cell receptor (TCR). When cocultured with CD4+CD25- cells, the CD4+CD25+ cells markedly suppressed proliferation by specifically inhibiting the production of IL-2. The inhibition was not cytokine mediated, was dependent on cell contact between the regulatory cells and the responders, and required activation of the suppressors via the TCR. Inhibition could be overcome by the addition to the cultures of IL-2 or anti-CD28, suggesting that the CD4+CD25+ cells may function by blocking the delivery of a costimulatory signal. Induction of CD25 expression on CD25- T cells in vitro or in vivo did not result in the generation of suppressor activity. Collectively, these data support the concept that the CD4+CD25+ T cells in normal mice may represent a distinct lineage of "professional" suppressor cells.

IL-12 unmasks latent autoimmune disease in resistant mice.

Inbred mice exhibit a spectrum of susceptibility to induction of experimental allergic encephalomyelitis (EAE). We have compared the immune responses of the susceptible SJL (H-2s) and resistant B10.S (H-2s) strains to determine factors other than the MHC background which control resistance/susceptibility to EAE. The resistance of the B10.S strain was found to be secondary to an antigen-specific defect in the generation of Th 1 cells that produce IFN gamma. This defect in IFN gamma production could be restored by exposure of the myelin basic protein (MBP)-reactive T cells to IL-12 with the subsequent induction of the ability to transfer EAE to naive recipients. These findings have important implications for the therapeutic use of IL-12 and IL-12 antagonists and may explain the association between relapses/exacerbation of autoimmune disease and infectious diseases.

Alloantiserum-induced inhibition of immune response gene product function. I. Cellular distribution of target antigens.

It has been previously shown that alloantisera prepared by reciprocal immunization of strain 2 and strain 13 guinea pigs specifically block the activation of T lymphocytes from immune guinea pigs by antigens, the response to which is controlled by Ir genes. In this report we have examined the effect of absorption of the 13 anti-2 serum with different populations of lymphoid cells. It is unlikely that the inhibitory activity of the anti-2 serum on the proliferation of (2 x 13)F(1) lymphocytes to a DNP derivative of a copolymer of L-glutamic and L-lysine (DNP-GL) is due to the presence of antibodies specific for the unique antigenic determinants (idiotypes) of clonally distributed T-lymphocyte receptors. Thus, cells obtained from a normal animal and a DNP-GL immune animal were equivalent in their absorptive capacity. Populations of T lymphocytes were ineffective in absorbing either the cytotoxic or inhibitory activity of the anti-2 serum, while L(2)C leukemia cells, a malignant B-cell population, were most efficient in absorbing both activities. Thus, the antigen(s) against which the cytotoxic and inhibitory activities are directed are present to a greater extent on B lymphocytes than on T lymphocytes. However, these results do not allow us to definitively determine whether the inhibitory activity of the alloantisera is due to antibodies specific for Ir gene products or antibodies specific for linked antigens in the MHC. We also examined the effect of a number of anti-immunoglobulin reagents which had specificity for the heavy and/or light chains of guinea pig immunoglobulin on the in vitro lymphocyte proliferative response to antigen. Under conditions in which we were able to completely and specifically suppress the response of (2 x 13)F(1) lymphocytes to DNP-GL with anti-2 serum, the anti-immunoglobulin reagents were devoid of inhibitory effect on the response of these same F(1) cells to DNP-GL, a copolymer of L-glutamic and L-tyrosine (GT), or purified protein derivative of tuberculin (PPD). These results strongly suggest that conventional serum-type immunoglobulin is not important in antigen recognition by the T cells involved in the DNA synthetic response.

Alloantiserum-induced inhibition of immune response gene product function. II. Genetic analysis of target antigens.

It has been previously demonstrated that alloantisera can specifically block the activation of T lymphocytes by antigens, the response to which is linked to the presence of histocompatibility (H) types against which the alloantisera are directed. Thus, strain 13 anti-2 serum can inhibit the activation of (2 x 13)F(1) T lymphocytes by a DNP derivative of a copolymer of L-glutamic acid and L-lysine (DNP-GL), an antigen the response to which is controlled by a 2-linked Ir gene. It was proposed that alloantisera can inhibit T-lymphocyte antigen recognition through interference with the activity of immune response (Ir) gene products. In order to further study whether the inhibitory antibodies within the alloantisera are directed against H antigens or against the products of the Ir genes, we have examined whether the anti-2 serum can inhibit the function of an Ir gene (the L-glutamic acid and L-alanine [GA] gene), which is normally linked to strain 2 H genes when this gene occurs in an outbred animal lacking strain 2 H genes. In the majority of cases, the anti-2 serum was capable of inhibiting the in vitro proliferative response to GA of T cells derived from animals that were GA(+)2(+), but the serum had little if any effect on the GA response of T cells from GA(+)2(-) animals. Furthermore, an antiserum prepared in strain 13 animals against the lymphoid cells of a GA(+)2(-) outbred animal was devoid of inhibitory activity on the GA response of cells from a (2 x 13)F(1), while an antiserum prepared in strain 13 animals against the lymphoid cells of a GA(+)2(+) outbred animal was capable of specifically inhibiting the response to GA. It thus appears that the inhibition of the GA response by the anti-2 serum is primarily mediated via antibodies directed toward strain 2 H antigens rather than antibodies specific for the product of the GA Ir gene. The mechanism of alloantiserum induced suppression of Ir gene function would then be by steric interference with the Ir gene product on the cell surface, rather than by direct binding to it. This conclusion implies that the products of both the H genes and the Ir genes are physically related on the cell surface. The implications of such a relationship in terms of the fluid-mosaic model of the lymphocyte surface are discussed.

Antigen-specific activation, tolerization, and reactivation of the interleukin 4 pathway in vivo.

The outcome of immune responses critically depends on the pattern of lymphokines secreted by CD4+ T cells. CD4+ T cells may differentiate into interleukin 2 (IL-2) and interferon gamma secreting T helper 1 (Th1)-like cells or IL-4/IL-5/IL-10 secreting Th2-like cells. However, the mechanisms that regulate production of IL-4 or other T cell lymphokines in vivo remain unknown. We use the superantigen, Staphylococcus enterotoxin A (SEA), as a model antigen to characterize the signals that regulate the production of IL-4 in vivo. Induction of IL-4 in normal CD4+ T cells required stimulation with both antigen and IL-4. SEA-specific CD4+ T cells produced large amounts of IL-4 when restimulated within 10 d after in vivo priming. Repetitive application of both signals was required to prevent downregulation of IL-4 production. Although controversy exists regarding the susceptibility of Th2-like cells to tolerogenic signals, high doses of superantigen readily abolished the capacity to produce IL-4 in both naive T cells and in T cells already primed for IL-4 production. Infection with the nematode, Nippostrongylus brasiliensis, reversed the established T cell tolerance, whereas the signals which induced IL-4 production in normal T cells, antigen and IL-4, were not capable of reversing superantigen-specific tolerance in vivo. The major parameter that correlated with the capacity of parasitic infection to break tolerance was magnitude of the lymphoproliferation seen during the course of the infection. The capacity to activate or tolerize the IL-4 pathway in an antigen-specific fashion should prove useful in the design of antigen-specific therapies for autoimmune and allergic diseases.

Production of autoreactive I region-restricted T cell hybridomas.

We produced autoreactive T cell hybridomas that can be induced to secrete interleukin 2 by co-culture with either syngeneic splenic stimulator cells or syngeneic Ia-positive B cell-B lymphoma hybridomas. These autoreactive hybridomas arose from the fusion of pork insulin-primed lymph node T cells with the AKR thymoma BW 5147 and occurred at a higher frequency than the expected insulin-specific hybridomas. Mapping studies using recombinant strains and blocking studies using monoclonal anti-Ia antibodies localized the stimulatory determinant to the I-Ad subregion of the major histocompatibility complex. These T cell hybridomas did not appear to be directed at any foreign antigen present in the culture system because activation occurred in serum-free, insulin-free medium (Iscove's medium). Such hybridomas should prove to be a potent tool in studying the biologic significance and function of the autoreactive response.

Generation of T cell colonies from responder strain 2 guinea pigs that recognize the copolymer L-glutamic acid, L-lysine in association with nonresponder strain 13 Ia antigens.

T cells from nonimmune responder strain 2 guinea pigs were primed in vitro to the copolymer GL in association with allogeneic, nonresponder strain 13 PEC. T cells that recognized GL in association with strain 13 Ia were separated from alloreactive T cells by cloning the population in soft agar following the priming in liquid culture. The existence of T cells of responder origin that recognize antigen in association with nonresponder macrophages is most consistent with clonal deletion models of Ir gene function.

Nature of the antigenic complex recognized by T lymphocytes. I. Analysis with an in vitro primary response to soluble protein antigens.

In order to analyze the genetic factors involved in the regulation of macrophage-T-cells interaction we have developed an in vitro primary response to soluble protein antigens in which nonimmune guinea pig T cells can be sensitized and subsequently challenged in tissue culture with antigen-pulsed macrophages. Antigen-specific T-cell activation, as measured by increased DNA synthesis, occurred when syngeneic antigen-pulsed macrophages were used for both initial sensitization and secondary challenge. No T-cell activation occurred when allogeneic antigen-pulsed macrophages were used for secondary challenge of cells primed when syngeneic macrophages. When allogeneic antigen-pulsed macrophages were used in both primary and secondary cultures it was difficult to assess antigen-specific stimulation due to the substantial mixed leukocyte reaction. However, when T cells from F1 animals were primed with parental antigen-pulsed macrophages they responded only to the parental macrophages used for initial sensitization but not to those of the other parent. These results are discussed with respect to T-cell recognition of a complex antigenic determinant which may include I-region gene products.

Mutant lines of guinea pig L2C leukemia. I. Deletion of Ia alloantigens is associated with a loss in immunogenicity of tumor-associated transplantation antigens.

Five different lines of a strain 2 guinea pig leukemia (L2C) which had been carried in different laboratories share certain chromosomal markers and have a common surface immunoglobulin idiotypic determinant indicating that they have a common origin. All these leukemic lines have on their surface of the B alloantigen (equivalent of the murine H-2K and H-2D antigens) and four of these five lines have on their surface the Ia alloantigens normally present on the strain 2 lymphocytes. The result of a study of the growth and rejection patterns of these leukemias in inbred and random-bred guinea pigs of selected histocompatibility type indicates that both the B and Ia antigens can act as transplantation antigens in guinea pigs. Immunization protection tests in syngeneic animals demonstrated that the four Ia-positive leukemias possessed a tumor-associated transplantation antigen (TATA), while the one Ia-positive leukemias possessed a tumor-associated transplantation antigen (TATA), while the one Ia-negative leukemia by this criteria did not appear to have TATA. However, crisscross immunization protection tests demonstrated that preimmunization of syngeneic animals with an Ia-positive L2C line lead to a subsequent protection against challenge with the Ia-negative leukemia. Immunization with the Ia-negative line never protected against a subsequent challenge with any of the leukemic cells of L2C lines. These results strongly suggest that the Ia-negative leukemia possessed a TATA that can be recognized but is not itself immunogenic, and also indicate that Ia antigens on L2C cells are functionally associated with TATA and can act as immunological carries for tumor transplantation determinants.

Nature of the antigenic complex recognized by T lymphocytes II. T-cell activation by direct modification of macrophage histocompatibility antigens.

In order to analyze the molecular structures involved in T-cell recognition we developed an in vitro primary response against alloantisera bound to histocompatibility antigens in which nonimmune guinea pig T cells can be sensitized and subsequently challenged in tissue culture with antisera-treated macrophages. If macrophages were incubated with alloantisera directed against the I-region-associated (Ia) antigens of the guinea pig major histocompatibility complex (MHC) T cells could be sensitized to the antisera bound to macrophage Ia determinants. Anti-Ia-treated syngeneic macrophages in the first and second cultures elicited specific T-cell activation, as measured by increased DNA synthesis, to the antisera-induced immunogenic determinants. Similarly, antiIa-treated allogeneic macrophages also specifically stimulated T cells to antisera bound to allogeneic Ia determinants while reducing the mixed leukocyte reaction. Antisera to the B.1 antigens of the guinea pig MHC, the homologue of the mouse H-2K or H-2D antigens, also elicited specific T-cell activation that did not cross-react with that produced by the anti-Ia alloantisera. Furthermore, the anti-B.1-induced stimulation appeared to be associated with the Ia antigens of the macrophage used for priming since (2 x 13)F1 T cells sensitized with anti-B.1-treated parental macrophages could be restimulated only with the parental macrophage used for initial sensitization, and not with those of the other parent. Since the parental strain 2 and strain 13 guinea pigs express serologically identical B.1 antigens and differ only by Ia antigens of the MHC, this observation suggests that both B.1 and Ia antigens may be included in the immunogenic complex recognized by T cells. However, we cannot rule out the possibility that this restriction is due to other genetic differences between strain 2 and strain 13 guinea pigs that is unrelated to the I-region. We interpret these findings as showing that macrophage Ia antigens may serve to directly present antigens bound to the Ia molecule, and possibly indirectly aid in the presentation of antigens bound to other membrane components, such as the B.1 antigens.

Function of macrophages in antigen recognition by guinea pig T lymphocytes. II. Role of the macrophage in the regulation of genetic control of the immune response.

A number of recent studies have suggested that the main functional role of the product of the immune response (Ir) genes is in the process of antigen recognition by the T lymphocyte. The observation in the accompanying report that the interaction of macrophage-associated antigen with immune T lymphocytes requires that both cells share histocompatibility antigens raised the question as to whether the macrophage played a role in the genetic control of the immune response or even if the macrophage were the primary cell in which the product of the Ir gene is expressed. In the current study, parental macrophages were pulsed with an antigen, the response to which is controlled by an Ir gene lacking in that parent; these macrophages were then mixed with T cells derived from the (nonresponder x responder)F(1) and the resultant stimulation was measured. No stimulation was seen when column-purified F(1) lymph node lymphocytes were mixed with antigen-pulsed macrophages from the nonresponder parent. However, when the highly reactive peritoneal exudate lymphocyte population was used as the indicator cells, parental macrophages pulsed with an antigen whose Ir gene they lacked were capable of initiating F(1) T-cell proliferation. The magnitude of stimulation was approximately 1/10 that seen when macrophages from either the responder parent or the F(1) were used. In order to explain this observation, we hypothesize that antigen recognition sites on the T lymphocyte are physically related to a macrophage-binding site and both are linked to the serologically determined histocompatibility antigens. Thus, parental macrophages pulsed with an antigen, whose Ir gene they lack, activate F(1) cells poorly because the recognition sites for the antigen are physically related to the macrophage-binding site of the responder parent while the main contacts between the cells are at the nonresponder binding sites. Experiments performed with alloantisera lend support to this hypothesis. Thus, when parental macrophages are pulsed with any antigen and added to F(1) T cells, an alloantiserum directed against parental histocompatibility antigens reacts with both the lymphocyte and the macrophage and thereby inhibits macrophage-lymphocyte interaction and abolishes antigen-induced lymphocyte transformation. When the alloantisera are directed at determinants present solely on the T lymphocyte, they only inhibit the recognition of antigens controlled by the Ir gene linked to the histocompatibility antigen against which they are directed. We conclude from these studies that antigen recognition by the T lymphocyte is a complex multicellular event involving more than simple antigen binding to a specific lymphocyte receptor.

Function of macrophages in antigen recognition by guinea pig T lymphocytes. I. Requirement for histocompatible macrophages and lymphocytes.

Antigen activation of DNA synthesis in immune thymus-derived lymphocytes of guinea pigs requires the cooperation of macrophages and lymphocytes. We have investigated the role of histocompatibility determinants in this macrophage-lymphocyte interaction using cells from inbred strain 2 and 13 guinea pigs. The data demonstrate that efficient presentation of macrophage-associated antigen to the lymphocyte requires identity between macrophage and lymphocyte at some portion of the major histocompatibility complex. The failure of allogeneic macrophages to effectively initiate immune lymphocyte proliferation was not the result of the presence of an inhibitor of blastogenesis released in mixtures of allogeneic cells, peculiarities of the antigen or lymphoid cells employed, nor differing kinetics of activation by allogeneic macrophages. In addition, data were presented that demonstrated that alloantisera inhibit lymphocyte DNA synthesis by functional interference with macrophage-lymphocyte interaction.

Histocompatibility-linked immune response gene function in guinea pigs. Specific inhibition of antigen-induced lymphocyte proliferation by alloantisera.

A number of autosomal dominant immune response (IR) genes have been identified in both mice and guinea pigs. These IR genes have been shown to be linked to the major histocompatibility antigens of the species and to be functionally expressed primarily in T lymphocytes. In order to more fully understand the relationship between IR genes, histocompatibility antigens, and immune recognition, the effect of specific alloantisera on lymphocyte stimulation induced by antigens under control of IR genes was examined. Using lymphocytes from strain 2 or strain 13 animals, the in vitro proliferative responses both to antigens which are known to be under genetic control (DNP-GL in strain 2 guinea pigs and GT in strain 13 guinea pigs) and to an antigen which is not known to be under genetic control (PPD) were inhibited to a similar degree and to a much greater extent than the response to phytohemagglutinin. However, when cells from F(1) (2 x 13) animals are used, the alloantisera markedly inhibit only the response which is linked to the histocompatibility antigens against which the serum is directed. Thus, the anti-2 serum inhibited the response to DNP-GL but not to GT; the anti-13 serum inhibited the response to GT but did not affect DNP-GL response. The inhibitory activity of the alloantisera could not be removed by absorption with gamma globulin of the opposite strain. It can be concluded from these observations that immune response genes produce a cell surface-associated product and that this product plays a role in the mechanism of antigen recognition by the T lymphocyte. The mechanisms by which alloantisera block this process of antigenic recognition is not resolved nor is the relationship between the IR gene product and the antigen-binding receptor of the T lymphocyte. The approach described here offers a powerful tool for the resolution of these problems.

The vitronectin receptor serves as an accessory molecule for the activation of a subset of gamma/delta T cells.

Constitutive production of cytokines was observed in 3 of 12 gamma/delta T cell lines derived from murine epidermis and correlated with the expression of the C gamma 4, V delta 6 T cell receptor (TCR). After adaptation of one of the lines (T195/BW) to serum-free culture conditions, cessation of the "spontaneous" production of interleukin 4 (IL-4) was observed and IL-4 production could then by induced by the addition of RGD-containing extracellular matrix (ECM) proteins to the culture. The response to the ECM proteins could be completely inhibited by a mAb to the murine vitronectin receptor (VNR). However, the induction of IL-4 production could also be inhibited by anti-CD3 and by an anti-clonotypic mAb to the TCR-gamma/delta of T195/BW. As TCR-gamma/delta loss mutants of T195/BW also failed to respond to ECM proteins, these data demonstrate that engagement of the VNR by its ligand is necessary, but not sufficient, for the induction of IL-4 production. Furthermore, the VNR is expressed by many other T cell clones (both gamma/delta and alpha/beta), none of which produce lymphokines constitutively. Taken together, these observations strongly favor the view that not only is coexpression of the VNR and TCR required for the induction of IL-4 production, but that the TCR must also be engaged by its ligand, most likely a cell surface antigen expressed by the hybridoma itself.

The mouse vitronectin receptor is a T cell activation antigen.

In this report, we demonstrate that the T cell activation antigen, recognized by monoclonal antibody H9.2B8, is the murine homologue of the vitronectin receptor (VNR) and, thereby, we provide initial evidence that VNR is expressed on lymphoid cells. VNR is expressed on a variety of T cell lines, tumors, and Con A-activated splenocytes, but not resting T cells, and is capable of binding to the extracellular matrix proteins fibronectin, fibrinogen, and vitronectin, via the tripeptide sequence RGD. There was no evidence of novel beta chains pairing with the VNR alpha chain, as has been demonstrated in some human cells. In view of recent studies demonstrating that this molecule functions as an accessory molecule in T cell activation, the VNR may play an important role in mouse T cell functions.

Regulation of interleukin (IL)-12 receptor beta2 subunit expression by endogenous IL-12: a critical step in the differentiation of pathogenic autoreactive T cells.

The interleukin (IL)-12 receptor (R)beta2 subunit is the critical molecule involved in maintaining IL-12 responsiveness and controlling T helper cell type 1 lineage commitment. We demonstrate that IL-12 and interferon (IFN)-gamma play separate, but complementary, roles in regulating IL-12Rbeta2 expression on antigen-specific CD4(+) T cells. These results are consistent with our previous observation that IL-12 can promote autoimmune disease through IFN-gamma-independent as well as -dependent pathways. Therefore, we compared the induction of IL-12 by, and the expression of the IL-12Rbeta2 subunit on, myelin basic protein (MBP)-specific T cells from experimental allergic encephalomyelitis (EAE)-susceptible SJL (H-2(s)) mice and from EAE- resistant B10.S mice (H-2(s)). B10.S mice had an antigen-specific defect in their capacity to upregulate the IL-12Rbeta2 subunit. Defective expression was not secondary to the production of suppressive cytokines, but to a failure of B10.S MBP-specific T cells to upregulate CD40 ligand expression and to induce the production of IL-12. IL-12Rbeta2 expression as well as encephalitogenicity of these cells could be restored by the addition of IL-12. These results suggest that the development of immunotherapies that target the IL-12Rbeta2 subunit may be useful for the treatment of autoimmune diseases.