The feeding of cloned helper T cells by irradiated spleen cells results in the modulation of T-cell antigen receptors (TCRs) as detected by FACS. When two groups of anti-TCR antibodies--anti-idiotypic and anti-V beta--are compared, time-dependent patterns of modulation of TCR are drastically different. Whereas up to 80% of the idiotypic determinants disappear within 2 days after stimulation, almost no change is observed for the determinants recognized by V beta-specific antibodies within the same period. Sequential immunoprecipitations clearly showed that anti-idiotypic and anti-V beta antibodies recognize the same population of TCR. Moreover, surface labelling followed by immunoprecipitation of TCR did not show rapid and drastic changes in the amount of specifically precipitated material. The modulation is not significantly affected by the addition of specific antigen, but is specific for the clone's MHC restriction element. Functionally, the modulation of TCR epitopes affects the ability of anti-TCR antibody but not of the MHC/antigen complex to stimulate T cells. We conclude that the observed modulation of fluorescence intensity in the TCR complex after MHC recognition (1) is epitope specific, (2) is independent of the presence of nominal antigen and (3) does not affect the efficiency of antigen-specific stimulation.
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