Effect of Cross Reactions on HL‐A Antigen Immunogenicity

The sera of 172 HL‐A typed subjects immunized mostly by multiple transfusions were studied and the specificities of the produced HL‐A antibodies were determined. The probability of non‐response against an antigen cross reacting with an antigen of the immunized subject was calculated by the use of Bayes’ method. A lower immunogenicity within the main cross reacting groups (CREG) was confirmed: [HL‐A2, W28], [HL‐A3,1,11], connected to [HL‐A10, W19 (= W29,30,31,32)], [W5, HL‐A5, W15,W21], [HI‐A7,W10,W22]. Some antigens were not connected to any CREG: HL‐A9,12,13, W27. Others were insufficiently studied in the material to allow definite conclusions: W18,W14,HL‐A8. An asymmetry of the phenomenon i.e. non reciprocal inhibition of antibody production for two antigens was observed often. The comparison of one part of the material studied with the platelet complement fixation test, to another part studied with the lymphocytotoxicity technique suggested that the specific inhibition of antibody production was not complete but that such a situation only decreased the frequency and intensity of the response against the antigen. A study of the co‐occurrence of various HL‐A specificities in the immune sera lead to a similar but somewhat broader description of the CREG.