Suppression of the cytotoxic T cell response to minor alloantigens in vivo. Linked recognition by suppressor T cells

Modulating the Th1/Th2 balance in inflammatory arthritis

The balance between Th1 and Th2 cells regulates the choice between inflammatory and antibody-mediated immune responses. To an increasing extent this balance is thought to involve the participation of antigen-presenting cells, rather than the entirely autonomous activity of T cells and their cytokines. Here we survey current opinion concerning the working of this balance, and its condition in rheumatoid arthritis and the other inflammatory arthritides. The contrast between Lyme arthritis and reactive arthritis is particularly illuminating, since one is triggered by extracellular and the other by intracellular infection. We describe current approaches to the modulation of this balance. Guided by the principles that genetic polymorphism is likely to identify relevant genes, that any cytokine gene picked up by a virus must matter and that natural immunosuppressive activity at mucosal surfaces should be worth exploiting, we identify as particularly worthy of attention: (i) IL-10, (ii) inhibitors of IL-12 production, (iii) inhibitors of CD40 ligand expression and (iv) oral and nasal tolerance. Other protective T cell subsets are touched on, and the impact of oligonucleotide arrays mentioned.

Induction of linked suppression in addition to the donor H-2 class I-specific unresponsiveness in recipient T cells by transfusing class I plus class II-disparate, but not class I alone-disparate, bone marrow cells

This study was undertaken to determine whether bone marrow (BM) cells contain a cell population with the capacity to induce an unresponsiveness of T cells specific to the BM self-H-2 class I antigens in vivo, i.e., veto cell population. Recombinant or congenic mice were infused intravenously with H-2-incompatible BM cells. One to several weeks later, donor H-2-and irrelevant H-2-specific responses in mixed lymphocyte reaction cultures of recipient T cells were assessed. Transfusion of H-2-incompatible BM of C57BL/10 (B10) recombinant strains caused a long-lasting cytotoxic T lymphocyte (CTL) unresponsiveness to the donor class I antigens in recipient lymph node cells. When class I plus class II-disparate BM cells were transfused, an anti-donor class I CTL response and a response against a third-party class I antigen, which was presented on the stimulator cells coexpressing the donor class I and class II, were significantly suppressed. This linked suppression lasted for less than 2 weeks after transfusion. Transfusion of class I-alone-disparate BM induced the donor class I-specific CTL unresponsiveness, but not the linked suppression. The induction of linked suppression was prevented considerably by transfusing nylon wool-nonadherent BM or by treating recipients with cyclophosphamide 2 days before transfusion. An anti-third-party class I CTL response, stimulated in vitro with fully allogeneic spleen cells, was not hampered by the BM transfusion. Coculturing the lymph node (LN) cells obtained from the class I plus class II-disparate BM recipient with normal LN cells interfered with the generation of both anti-donor class I and anti-linked third-party class I CTL, whereas, coculturing LN cells from the class I alone-disparate BM recipient inhibited neither specificity of CTL generation. Transfusion of class I plus class II-disparate BM resulted in a significant suppression of the donor class II-specific proliferative response. In contrast, transfusion of class I alone-disparate BM did not suppress any proliferative responses, including even a "linked" third-party class II-specific response. Transfusion of bm 1, (B6 X bm 1)F1, or (bm 1 X bm 12)F1 BM to B6 did not induce unresponsiveness in bm 1-specific CTL responses. However, the transfusion resulted in a significant suppression of bm 1-reactive proliferative response of recipient LN cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Autologous CD8-positive cells suppress T cell proliferation in response to thyroid antigens in Hashimoto's thyroiditis

To assess whether there is a defect in thyroid antigen-specific suppressor cells in Hashimoto's thyroiditis (HT) and whether such cells actively prevent thyroid autoreactivity in control subjects, T cell proliferation was measured before and after removal of CD8-positive cells from the lymphocyte population. CD8 depletion significantly increased the proliferation of HT lymphocytes to soluble thyroglobulin and to thyroid microsomal antigen immunoblotted onto nitrocellulose; some of these cultures also reacted with an unidentified thyroid antigen, mol wt approx 16 kDa. However, CD8 depletion did not permit normal lymphocytes to respond to thyroid antigens. Peripheral blood CD8 cells were also found to suppress proliferation of a thyroid T cell line, derived from a patient with HT, in response to autologous, Ia-positive thyroid follicular cells. These results do not support the existence of a defect in antigen-specific suppressor cells in HT, nor the active suppression of thyroid autoreactivity by such cells in normal subjects. The data suggest that there may be an imbalance in T cell helper and suppressor influences in thyroiditis, but in some patients a new balance is achieved, so that T cell sensitization to thyroid autoantigens can only be identified by removal of CD8-positive cells.

T cells in transplantation immunity

This paper reviews the following problems in transplantation immunity: (i) short-lived ability to transfer immunity or suppression, in contrast to long-lived immunological memory in the autochthonous animal; (ii) short-lived ability to transfer graft-resistance, in contrast to long-lived ability to transfer helper activity for B-cells; (iii) the response to H-Y, as a system that might solve some outstanding problems in antigen presentation; and (iv) the contrast between live and killed allogeneic cells as immunogens. All of these problems, it is suggested, are amenable to study by modern methods. Students like me were drawn into Peter Medawar's orbit in the 1940s and 1950s by an irresistible mix of intellectual challenge and the glamour of experimental surgery. Much the same was happening elsewhere in the laboratories of Ray Owen, Milan Hasek, George Snell, Burnet, and Florey, and by 1960 the transplantation immunologists could justly claim to have opened up a whole new area of ideas in biology: we had discovered the lymphocyte as the antigen-sensitive cell, and the principles of immunological tolerance; we had revived interest in cellular immunity, and it was we who found the MHC (even if we had little idea of its real meaning). But by 1960 the first wave of success had passed, and the penetration of immunology by molecular biology had begun. Interest in transplantation immunity perceptibly declined, although many groups continued to address important problems, particularly in the field of organ transplantation. (ABSTRACT TRUNCATED AT 250 WORDS)

Three-cell-type clusters of T cells with antigen-presenting cells best explain the epitope linkage and noncognate requirements of the in vivo cytolytic response

Using an established i.p. adoptive transfer system in which primed precursors of cytolytic (Tc) cells are combined with primed helper (Th) cells and alloantigen, the three-cell-type hypothesis of T-T cooperation has been tested. This hypothesis assumes that cooperation takes place through the formation of clusters, consisting of one or more Tc precursors plus one or more Th cells binding to antigen on the surface of antigen-presenting cells (APC). By using antigens in which the H-2Db epitopes recognized by the Tc precursors are presented either on the same cell as the BALB minor histocompatibility epitopes recognized by the Th cells, or a different one, the value of epitope-linkage has been explored. Epitope-linkage is found to enhance the response at low concentrations of antigen but not at high ones, in accordance with the prediction that at low concentrations individual APC will usually take up either one antigen or the other but not both from an unlinked mixture, while at high concentrations most APC will take up both whether they are linked or not. In a further test of this hypothesis, no requirement for a cognate T-T interaction could be detected. With the three-cell-type interaction thus better established, its implications in terms of efficiency compared with linked-cognate interactions and its evolution are discussed.

Induction and persistence of suppression of contact hypersensitivity against bystander haptens and alloantigens in rats

The shift of suppression from a tolerizing hapten to a so-called bystander antigen was investigated in this study using contact hypersensitivity to trinitrochlorobenzene (TNCB) and dinitrofluorobenzene (DNFB) and delayed type hypersensitivity (DTH) to alloantigens in the rats as experimental models. Primary suppression of contact hypersensitivity was induced by intravenous injection of the water-soluble forms of TNCB and DNFB. A shift of the suppression to the bystander hapten was found if the tolerizing and bystander hapten were mixed and applied to the same area of skin during the sensitization procedure, but not if they were applied to separate areas of skin. With alloantigens, bystander suppression developed only when the sensitizing allogeneic cells were mixed with hapten-modified syngeneic cells. It was not induced by hapten-modified allogeneic cells. Once induced, such bystander suppression of the response to haptens persisted independently of the primarily tolerizing hapten, and it could be adoptively transferred with spleen cells. These results favour the concept that the bystander suppression is mediated by the non-specific action of suppressor cells generated specifically during the mixed sensitization rather than by an antigen bridge.

Suppression induction in vivo by a T helper clone?

We have previously described a helper T cell clone which augments in vivo cytotoxic T cell responses when injected at 10(4) cells per mouse, but not at 10(5) per mouse (Crispe, I. N. et al., Immunology 1984. 52:55). To test whether this dose-response relationship was due to the induction of suppression, naive syngeneic mice were injected with 10(5) cloned T helper cells, and their spleen cells were subsequently assayed for suppressive activity in adoptive transfer experiments. Lymphocytes from such mice indeed suppressed an antigen-specific cytotoxic response, but only in the presence of the same T helper cell clone freshly added at the time of adoptive transfer. On this basis we argue that the distinction between T helper cell activity and T suppressor-inducer activity corresponds to differences in cell numbers, rather than to two separate cell lineages.

Suppression of the cytotoxic T cell response to minor alloantigens in vivo. II. Fine specificity of suppressor T cells and lack of restriction by immunoglobulin heavy chain-linked gene products

While it has been widely reported that some subsets of suppressor T cells are restricted by products of immunoglobulin heavy chain genes (particularly the variable region gene), we have been unable to find evidence for such interactions in the suppression of the primary in vivo cytotoxic T cell response to minor alloantigen. We have also examined the repertoire of the suppressor T cells active in this system and find that they recognize a different set of antigens from cytotoxic T cells, out of the same available pool of minor antigens.

Skin graft rejection and delayed-type hypersensitivity responses to H-Y in an I-Ab mutant

Based on graft rejection in C57BL/6 and B10.A(4R), but not in B10.A mice, skin graft rejection and delayed-type hypersensitivity (DTH) responses to the male HY antigen were considered to be under the control of the "IBb" gene in the mouse H-2 complex. These two phenomena were re-examined in the B6.C-H-2bm12 mutant strain [mutation in the A beta gene in IA leading to an alteration in Iab serologically detected specificities and the inability to generate cytotoxic T (Tc) cells to H-Y]. In this study the bm12 mutant was shown to produce weak DTH responses to H-Y. By contrast, bm12 female mice were unable to reject male skin grafts unless they had received prior footpad priming of male spleen cells, when graft rejection occurred, albeit slowly. In C57BL/6 mice the response to the HY antigen therefore appears to be solely under the control of the IAb gene. In other strains, response/nonresponse is presumably dictated by the ability of IA/IE interactions to produce T-helper responses.