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Journal of Experimental Medicine, Vol 177, 1541-1550, Copyright © 1993 by Rockefeller University Press
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SC Jameson, FR Carbone and MJ Bevan
Howard Hughes Medical Institute, Department of Immunology, University of Washington, Seattle 98195.
A previous report showed that the proliferative response of helper T cells to class II major histocompatibility complex (MHC)-restricted antigens can be inhibited by analogues of the antigen, which act as T cell receptor (TCR) antagonists. Here we define and analyze peptide variants that antagonize various functions of class I MHC-restricted cytotoxic T lymphocyte (CTL) clones. Of 64 variants at individual TCR contact sites of the Kb-restricted octamer peptide ovalbumin257-264 (OVAp), a very high proportion (40%) antagonized lysis by three OVAp- specific CTL clones. This effect was highly clone specific, since many antagonists for one T cell clone have differential effects on another. We show that this inhibition of CTL function is not a result of T cell- T cell interaction, precluding veto-like phenomena as a mechanism for antagonism. Moreover, we present evidence for direct interaction between the TCR and antagonist-MHC complexes. In further analysis of the T cell response, we found that serine esterase release and cytokine production are susceptible to TCR antagonism similarly to lysis. Ca2+ flux, an early event in signaling, is also inhibited by antagonists but may be more resistant to the antagonist effect than downstream responses.
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