Detection of HLA-DRw specificities by mixed agglutination

By means of mixed agglutination test with staphylococcal protein A indicator system, DRw antigens were studied on lymphocytes obtained from tonsils, peripheral blood and thymuses. Monospecific antisera to DRw 1, 2, 3, 6 and 7 which were preadsorbed with pooled platelets gave mixed agglutination titers of 300 or more against B cells of human tonsilar lymphocytes and peripheral blood lymphocytes. The DR phenotypes of human tonsilar lymphocytes and peripheral blood lymphocytes determined by mixed agglutination tests corresponded to those established by lymphocytotoxicity tests. Upon stimulation of thymocytes or T cells of peripheral blood lymphocytes by Con-A, DRw antigens became detectable by mixed agglutination tests. Simultaneous experiments on the stimulated T cells of peripheral blood lymphocytes by membrane fluorescence tests showed that 21-45% of the stimulated T cells possessed DRw antigens at a detectable level, while less than 2% of unstimulated cells were positive. These results indicated that DRw antigens are present in the subpopulation of T cells which may expand in the response to Con-A stimulation.