Further studies on the biological properties of guinea-pig IgG1 antibodies. III. Haemolytic efficiency in vitro.

The capacity of non-reciprocally contaminated guinea-pig IgG1 and IgG2 antibodies for sensitizing antigen-coated sheep erythrocytes for lysis was studied in the presence of serial dilutions of normal guinea-pig serum as the source of complement. IgG1 antibodies were highly efficient, provided complement was little diluted and not heated at 56 degrees. Chelation of Ca2+ by EGTA affected lysis of IgG1-sensitized cells by only 50%, while completely blocking lysis of IgG2-sensitized cells. The F(ab')2 fragment of IgG1, in contrast to the F(ab')2 fragment of IgG2, was almost as efficient as the parent antibody.