Cross reactivity in the HLA region.

Cross-reactivity in the HLA region was studied by adsorbing each of 33 monospecific HLA antisera individually with known platelets from 90 different donors. The residual cytotoxicity following adsorption in each combination of platelet sample and antiserum was assessed against known homologous target lymphocytes. This study has confirmed a majority of the previously known cross-reactive pattern and has revealed new patterns. A more significant observation is that allelic cross-reactivity of broad antigens such as A9, A10 and Bw16, was somewhat narrowed to a given split of these antigens in several instances; e.g., cross-adsorption of A1 antiserum by Aw24, and not Aw23; of A2 antiserum by A26, and not A25; and of B5 antiserum by Bw39, and not Bw38.