Depletion of IgG in rabbit sera by absorption with some group A streptococci.

Streptococci group A, type M 1 or M 56 were capable to deplete IgG in normal rabbit sera during absorption by means of a surface Fc receptor. One absorption with 8.0 mg (dry weight) M 1 streptococci or two absorptions with 71 mg M 56 streptococci removed all IgG in 0.2 ml rabbit serum diluted 1:10 (containing 1.5 mg IgG/ml). Antibodies to egg albumin and antibodies to sheep red cells were not demonstrable after absorption of 0.2 ml serum diluted 1:10 with 16.0 mg M 1 streptococci. These results are discussed in relation to some reports on immunologic cross-reactions between streptococci and mammalian tissues.