Autologous Agglutinators to Erythrocytes Sensitized with the Ripley Anti-Rh Antibody Digested with 14 Different Proteolytic Enzymes *t

lsologous antigenic determinants of y-globulin revealed by proteolytic digestion of the globulin molecules were discovered by Osterland, Harboe, and Kunkel (1963) in human lgG and by Mandy, Fudenberg, and Lewis (1965) in rabbit y G. These determinants are detected by autologous and isologous antibodies found in most human sera and in all rabbit sera, respectively. These antibodies were named pepsin agglutinators (Natvig, 1966a and b) for pepsin digested human globulins and homoreactant (Mandy, et al., 1965) for digested rabbit globulins. Subsequent studies with human globulins have shown that these serum agglutinators are primarily 7S; are usually specific for the enzymatic modification of the globulin molecule (Waller, in press); are distinct from other anti-globulin antibodies (Harboe et al., 1965); are found in most human sera albeit in low titer (Waller and Blaylock, 1966); and the titers of the pepsin agglutinators are not readily influenced by other immunologic events occurring in the individual.