T cell activation by anti-idiotypic antibody: mechanism of interaction with antigen-reactive T cells.

It has been shown that the activation of T cells by an anti-idiotypic antibody (anti-Id) TB71 containing an internal image of the corresponding mycobacterial antigen (38 kDa) was achieved by the interaction of anti-Id TB71 with the T cell receptor complex (CD3/Ti). The accessory cell requirement in this response could not be replaced by anti-Id TB71 coupled to Sepharose beads and was not inhibited by Fc receptor blockade. When taken together with the finding that anti-Id TB71-induced proliferation of a T cell clone was restricted by determinants encoded by the major histocompatibility complex, these findings suggested that anti-Id TB71 was presented to 38-kDa antigen-reactive T cells by the same mechanisms as conventional antigenic determinants. That is, both stimulated T cells through the CD3/Ti complex and had to be presented in the context of class II molecules on accessory cells. The finding that the disruption of the integrity of the anti-Id TB71 combining site did not affect T cell responsiveness although antibody binding was ablated implied that anti-Id TB71 may be partially degraded and re-expressed with MHC class II determinants.