Striking inverse correlation between IgG anti-F(ab')2 and autoantibody production in patients with cold agglutination.

Previous experiments showed that the physiologic IgG anti-F(ab')2 antibody suppresses the response of human autoreactive B cells. In the present study, we analyzed the IgG anti-F(ab')2 antibody in 293 patients with cold agglutination (CA). Their average IgG anti-F(ab')2 titer was not much different (211 +/- 8.3) from that of 279 healthy persons (195 +/- 6.7). However, CA patients with high anti-F(ab')2 titers had low CA autoantibody titers and vice versa (P = .0028; rho = -0.175). The stratification of patients according to the auto-antibody's specificity (anti-I, anti-i, anti-Pr) showed an inverse correlation between anti-F(ab')2 and CA in the anti-I group (P = .0057; rho = -0.180). Interestingly, the association was present only in patients whose disease was caused by noninfectious agents (P < .0001; rho = -0.423). The inverse correlation argues for an important role of the IgG anti-F(ab')2 in the regulation of autoantibody production in CA patients.