Studies of Incomplete Antibodies I. Effect of Papain on Red Cells

By KI sI IO AH0 AND CHARLES L. CHRISTIAN I HE TREATMENT of red cells with some proteolytic enzymes has proved to be a suitable technic for the detection of a variety of blood group antibodies which coat but do not agglutinate erythrocytes in physiologic saline. The mechanism of this enzyme effect is not well understood. There is evidence that the antibodies revealed by the enzyme technic are not univalent.14 Possible bases of this enzyme effect have been discussed,58 and the question of enzymatic alterations of the erythrocyte surface antigens has been recently reviewed.9 Enzyme treatment increases the titers of many agglutinating antibodies, but in some systems-e.g., with mononucleosis agglutinins and sheep cells, the titers are lower due to a release of the corresponding receptors from the cells.9 In the present work, it is shown that a variety of agglutinating antibodies agglutinate papain-treated cells in higher titers than nontreated cells, and evidence is presented that the titer increase is not due to a separate type of incomplete antibody. Rather, it is suggested that a smaller number of antibody molecules are required for agglutination of papain-treated cells because of altered surface properties of erythrocytes.