The functional link between the immune suppression gene and Mhc class II molecules

Regulatory role of OX22high T cells in mercury-induced autoimmunity in the brown Norway rat

The monoclonal antibody OX22 defines a functional split within CD4+ T cells in the rat, with OX22high cells mainly producing interleukin 2 (IL-2) and interferon gamma and responsible for delayed-type hypersensitivity responses, and OX22low cells mainly producing IL-4 and -5 and responsible for providing B cell help. There are reciprocal interactions between OX22high and OX22low cells, and it has been suggested that the OX22low subset has a role in the prevention of autoimmunity. We have used OX22 in vivo to define the role of these subsets in mercuric chloride-induced autoimmunity in the Brown Norway rat. In this model, there is polyclonal B cell activation and animals develop widespread tissue injury. Treatment of thymectomized animals with OX22 led to a profound reduction in the number of OX22high T cells in the peripheral blood. OX22-treated animals consistently developed more severe tissue injury than controls given an irrelevant antibody of the same isotype. Control animals pretreated with broad spectrum antimicrobial drugs showed milder tissue injury, but this protective effect of antimicrobials was lost in OX22-treated animals. Transfer of naive T cells to OX22-treated animals provided protection, but if T cells were depleted in vitro of OX22high cells before transfer, this effect was lost. These data provide evidence for a protective immunoregulatory role for OX22high T cells in mercuric chloride-induced autoimmunity.

Mixed lymphocyte response-generated suppressor cell specificity in humans is major histocompatibility complex-restricted

To formally test the hypothesis that allospecificity of the human mixed lymphocyte response-generated suppressor cells is restricted to the major histocompatibility complex, 18 primary mixed lymphocyte responses, using peripheral blood lymphocytes of 10 HLA-typed families, were used to generate suppressor effector cells. Responder lymphocytes shared one HLA haplotype with the stimulator cells. At day 10, the effector cells were tested for their ability to suppress proliferation of 55 test mixed lymphocyte responses consisting of naive autologous lymphocytes as responders and irradiated cells from individual family members as stimulators. Suppression was predicted when the test culture stimulators expressed the same HLA haplotype to which the suppressor cells were primed. There was statistically significant correlation between suppression and HLA haplotype sharing (p = 0.0143). In 6 out of 13 assays, however, we observed suppression that was not predicted on the basis of relevant HLA haplotype sharing. These stimulators shared only HLA-A2 with the priming haplotype. HLA antigen sharing was not seen in the 7 remaining, nonsuppressed cultures. We conclude that, within families, the effector function of in vitro generated suppressor cells is restricted by the major histocompatibility complex.