Conversion of incomplete antibodies to direct agglutinins by mild reduction: evidence for segmental flexibility within the Fc fragment of immunoglobulin G.

Abstract

Reduction of interchain disulfide bonds converted some [human] Ig[immunoglobulin]G incomplete antibodies to direct hemagglutinins. This conversion occurred whether antibody was free in solution or bound to the red-cell surface. Reduced antibody permitted to reoxidize in air no longer behaved as a direct agglutinin; reversion to an incomplete antibody did not occur when reoxidation was prevented by S-alkylation. Mild reduction of the antibody may impart sufficient freedom to permit bridging between cells. The interheavy-chain disulfide bonds may restrict segmental flexibility within the Fc fragment of IgG.