Immune Cross-reactivity of Penicillin and Cephalothin

WE recently described positive direct Coombs tests in patients receiving sodium cephalothin 1 . Because most normal sera caused the in vitro agglutination of red cells coated with cephalothin, we concluded that some of the positive direct Coombs tests must be related to non-immune binding of a serum protein–cephalothin complex to the red cell surface. We also suggested the possibility that some of these test sera contained anti-penicillin agglutinins.