Regulatory influences on the response of rabbit T cells to concanavalin A and phytohaemagglutinin.

The proliferative response, induced in rabbit spleen cells by concanavalin A (Con A) and phytohaemagglutinin (PHA), is abolished when T cells are killed with antibody against rabbit thymus lymphocyte antigen (RTLA) in the presence of complement. The response was examined with purified spleen T cells, to which various helper cell fractions were added; it could be shown that B cells help the responding T cells. The helper effect in the response to PHA is abolished and the response to Con A is reduced by any manoeuvre which destroys or removes B cells. Help by B cells is given when helper cells have lost proliferative capacity as a consequence of mitomycin-C treatment. Spleen cells adhering to the walls of culture tubes help suspended T spleen cells in their response to Con A. This help could be abolished by complement mediated cell kill with antibody to rabbit bursal equivalent lymphocyte antigen (RABELA). On the other hand, the helper effect in Con A response was increased when T cells were removed. Thus the response of T cells to Con A is regulated by helper B cells and suppressor T cells.