Antibodies to genetic types of gamma globulin after multiple transfusions.

Seventeen of 24 sera from children who had received multiple transfusions contained agglutinating antibodies against a Gm factor absent in the individual's serum gamma globulin. Each of these agglutinators was highly specific for a single Gm factor, and all proved useful as reagents for genetic typing. The accumulated evidence indicates that they resulted from genetically foreign gamma globulin introduced by transfusion.