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 μg. of 7S antibody per million cells, this corresponds to a minimum of 8.3×10⁵ 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.