Incomplete warm hemolysins. II. Corresponding antigens and pathogenetic mechanisms in autoimmune hemolytic anemias induced by incomplete warm hemolysins.
The pathogenesis of autoimmune hemolytic anemias induced by incomplete warm hemolysins (IWHs) is only poorly understood. Sera from eight patients with mostly severe IWH-related autoimmune anemias allowed us to address some key elements of the pathogenetic process. With the use of a modified enzyme-linked immunoassay we could show that (i) IWHs bound to native RBCs and (ii) IWHs initiated the activation of the complement cascade on native RBCs up to the level of C3. The interaction of IWHs with their corresponding antigens on red blood cell membranes, which were pretreated with different enzymes, showed that despite serological uniformity there are at least two different types of IWHs: (i) IWHs reacting with phospholipase susceptible antigens (six of the studied sera) and (ii) IWHs reacting with antigens which are hardly, if at all, phospholipase susceptible (two of the studied sera). Aside from Rh antibodies, most IWHs apparently belong to a second category of RBC antibodies whose corresponding antigens can be inactivated by phospholipase treatment of the cell membranes. IWHs showed no specificity for Rh antigens or the antigens of the I/i-system.