IMMUNOREGULATORY CHARACTERISTICS OF THE IN-VITRO ANTI-SSDNA RESPONSE

Continuous blockade of B-cell antigen receptors (BCRs) with Fab alpha sIg prevents the anti-ssDNA response of high, but not low, density B c ells. Signaling via the BCRs, by prior exposure to crosslinking F(ab') 2 alpha sIg, had no effect on the spontaneous anti-DNA response, but p revented a lipopolysaccharide-induced anti-DNA response. Pretreatment with intact alpha sIg, which provides exogenously derived Fc signals, reduced the response. An Fc-signal-blocking agent, F(ab')2 anti-IgG-Fc antibody, increased the number of anti-DNA antibody-forming cells pro duced in the absence of exogenous IgG anti-ssDNA antibody. Thus, activ ation is dependent on the availability of the BCRs, prior BCR crosslin king does not interfere with activation, and endogenous IgG anti-ssDNA antibody limits the activation of anti-ssDNA-specific B cells most of which are T-cell independent. These results indicate that the anti-ss DNA response is driven through the BCR.