314 Electrophoretic Mobility and Agglutinability

I t has been recognized since 1954 (1) that the red cells of mice of some strains, notably A, can be specifically agglutinated more readily by anti-H-2 sera than those of others. This difference has been shown to apply to several 1t-2 antigens (2) and has been ascribed to a different cell concentration of antigenic determinants (3). Experience shows, however, that nonspecific agglutinability is also different. Thus, it is much more frequent to observe considerable rouleaux formation in the controls of reactions of A-strain erythrocytes than in those of C57BL/6 and its sublines. In studies using AutoAnalyzers (Technicon Corporation, Tarrytown, N.Y.) to measure hemagglutination induced by H-2-anti-H-2 reactions it has been necessary to carry out the procedure in media that enhance agglutination to different degrees, since conditions adequate for A red cells do not support significant agglutination of C57BL/6 erythrocytes. Convelsely, those under which C57BL/6 red cells are efficiently agglutinated lead to complete nonspecific clumping of A-strain erythrocytes (Contreras and Rubinstein, manuscript in preparation, Decary and Rubinstein, unpublished observations). These observations suggest that the agglutinability of mouse erythrocytes may vary for reasons unrelated to the concentration of antigen. I t remains possible, however, that variation in antigen density at the surface may have two independent effects on agglutination: a direct influence over antigen-antibody reactions, and a nonspecific one, favoring rouleaux formation, perhaps through a modification of electrical charges at the membrane.