γG Erythrocyte Autoantibodies: Comparison of in Vivo Complement Coating and in Vitro “Rh” Specificity¹

Panreacting γG antibodies were eluted from the red cells of 35 patients with positive direct Coombs' tests. Twelve patients had γG coated cells and 23 had γG + C coated cells. Six of 12 γG and 6 of 23 γG + C eluates showed “Rh” specificity by their failure to react with the Rh_null blood. After absorption with Rh_null cells, an additional γG eluate and seven γG + C eluates showed “Rh” specificity. In these eluates specificity was obscured by the presence of additional antibodies of other specificities and was not apparent until antibodies lacking “Rh” specificity were removed by absorption with Rh_null cells. These findings suggest that the γG antibodies from γG and γG + C coated cells are similar and provide additional support for the concept that surface configuration of red cells as well as the characteristics of antibodies involved may be important in determining whether γG autoantibodies coat erythrocytes with C.