Hemolytic plaque formation to allogeneic human type A and B red cells

Plaque-forming cells can be generated from peripheral blood lymphocytes provided that the lymphocytes are prestimulated by in vitro sensitization in the presence of pokeweed mitogen. Of 91 blood type O persons whose lymphocytes were stimulated with red cell A antigen, 52% responded with plaque formation, whereas of 40 type O persons whose lymphocytes were stimulated with red cell B antigen, only 20% produced plaques. Similarly, reciprocal stimulation of type A and B persons showed higher plaque formation (65%) when 23 type B persons were stimulated with A than when 48 type A persons were stimulated with B red cells (19%). An optimal dilution of sensitizing cells is necessary and maximum time of sensitization was approximately 7 days.