On the feedback regulation of humoral immune response. I. Evidence for 'B suppressor cells'.

Evidence has been presented that complete and antigen-specific immune inhibition can be obtained by 'B suppressor cells'. Transfer of spleen cells from twice-immunized (SRBC) donors to untreated syngeneic recipients resulted in antigen-specific inhibition of the hosts' immune response. The cell responsible for this phenomenon could be shown to be the 7S-producing B cell; participation of T cells and macrophages could be excluded. After a second immunization of the donors, these B cells remained inhibitory for more than 20 weeks in the donors as well as in the recipients after transfer. Passively administered specific IgG antibody caused a similar inhibition of the hosts' immune response, which, however, lasted for less than 9 weeks only. The extent of inhibition caused by transfer of hyperimmune cells was parallel to the number of transferred 7S producing cells. Since it could be demonstrated that memory cells were present at times when the transferred cell material had lost its inhibitory potency, we concluded that inhibition is not caused by the mere presence of these cells. Since the transferred cells regained their inhibitory capacity after non-specific activation with LPS, we concluded that a product of such activated cells--most likely the specific 7S antibody--was responsible for the observed inhibition. Thus, it is demonstrated that B cells may serve as 'suppressor cells' in appropriate transfer experiments. It is, however, concluded that this effect is basically mediated by produced IgG and may in its mechanism be identical to the phenomenon of antibody-mediated regulation of humoral immune response.