EFFECT OF ANTITHYMOCYTE GLOBULIN ON HISTOCOMPATIBILITY ANTIGEN RECOGNITION IN MAN

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Abstract
Nonmajor histocompatibility complex (non-MHC) antigens are important targets of graft rejection and graft-vs.-host disease in clinical transplantation. Little is known regarding immunity to non-MHC antigens. The effect of antihuman thymocyte globulin (ATG) on reactivity in autologous and allogeneic-mixed lymphocyte cultures and activity in a model of non-MHC antigen immunity, and the response to trinitrophenyl (TNP)-modified autologous cells were studied. Primary proliferative responses to autologous B lymphocytes, allogeneic cells, and TNP-modified autologous cells were all inhibited by ATG treatment. Secondary proliferative responses and cytotoxicity to TNP-modified autologous cells were inhibited, as was cross-reactive cytotoxicity to TNP-modified allogeneic cells. Apparently, both MHC-restricted and MHC-nonrestricted immune responses to modified self-antigens and, possibly, to non-MHC antigens are sensitive to ATG treatment. ATG may be useful in clinical situations in which the objective of immunosuppression is to inhibit immunity to non-MHC antigens, such as after HLA-matched kidney grafting or bone marrow transplantation.