ABSTRACT
Murine normal lymphoid tissues contain relatively high numbers of anti-BrMRBC RFC and PFC. In the bone marrow, these frequencies are inversely correlated probably due to different activation states of these anti-BrMRBC B cells. The sera from syngeneic, but not allogeneic, mice are able to inhibit the formation of these anti-BrMRBC plaques. This inhibition is enhanced when sera of LPS treated mice is employed. The inhibitory factor can be displaced from normal spleen cells by 10(-5) M phosphorylcholine (PC) hapten reversing the PFC inhibition. The dialyzed and concentrated supernatant from PC incubated splenocytes completely abolishes anti-BrMRBC PFC. Preliminary data suggest that the molecular weight of the inhibitory factor is higher than 600 KDa. We postulate an antiidiotype autoantibody nature for this inhibitory factor.