Inhibition of T cell proliferation by antibodies to synthetic peptides

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Abstract
While T cell proliferation to antigen in the presence of antigen‐presenting cells is well known to be readily inhibited by antibodies directed against Class II major histocompatibility complex (MHC) (Ia/HLA‐DR) products, it has not been possible to inhibit proliferation by antibodies directed against the antigen. Because of the implications of these observations for targets of T cell recognition, this phenomenon was reinvestigated using human T cell clones, recognizing a small (24 amino acid) synthetic peptide (termed p20) derived from the influenza hemagglutinin‐1 molecule. It was found that proliferation of clones to p20 was inhibited efficiently (> 90%), using p20 as antigen, and rabbit anti‐p20. Inhibition was possible either by coculturing p20 antigen and antibody to p20 with cloned T cells and antigen‐presenting (E−) cells, or by pulsing antigen‐presenting cells with antigen prior to a brief incubation with antibody before washing the E− cells and using them to stimulate cloned T cells. These results do not indicate why previous attempts had failed, but in view of the different techniques available now (cloned T cells, small synthetic polypeptides, and antibody raised against polypeptide) we investigated the influence of these parameters. It was found that, using cloned T cells, the form of the antigen was of importance, as antibody inhibition of the response to hemagglutinin or whole influenza A was much less apparent. These differences were interpreted as being due to greater access of anti‐p20 to p20 than to hemagglutinin or influenza. If uncloned T cell lines were used, inhibition was also much harder to detect. This was interpreted as masking of inhibition of the response of some clones in the line by interleukin 2‐induced recruitment.