REACTION OF 7S AND 19S COMPONENTS OF IMMUNE RABBIT ANTISERA WITH HUMAN GROUP A AND AB RED CELLS

Abstract

7S and 19S components of rabbit anti-A antibody, labelled with 131I, have been separated by chromatography on DEAE-cellulose. The reactions of these components with human group A1, A2 and AB red cells have been investigated. At saturation point A1 cells combine with 0.22 jug. of 7S antibody per million cells, this corresponds to a minimum of 8.3 x 105 A-antigen sites per cell. A2 cells can take up only one quarter as much antibody, and combine much less avidly with it than do A1 cells. Cells can take up only about one-fifth as many 19S as 7S antibody molecules. 19S antibody is more avid and, on a molecular basis, is 750 times more efficient at agglutinating red cells than 7S antibody. The significance of these findings is discussed with regard to the differences between A1 and A2 antigens, and the valency and mode of attachment to the red cells of the antibodies.