Studies on Cross Reactive HL‐A Antibodies by Elution with Platelets

To evaluate the actual frequency and complexity of cross reactive HL‐A antibodies, 268 eluates produced with platelets from 43 unselected sera of parous women containing cytotoxic, HL‐A specific antibodies were studied. With sera or eluates or both, 41 different cross reactions against antigens of the second and 6 against antigens of the first locus were demonstrated. Although the antigens most frequently involved were HL‐A 2, 5 and 7, it was difficult to delineate “cross reacting groups”. There was an obvious interdependence between the specificities of cross reactive antibodies and the antigens of the serum producer. With respect to the fathers' antigens, the occurring antibodies were usually broader than expected. RNEP (Reaction Negative‐Elution Positive)‐phenomena were found with 30 eluates derived from 21 sera.