Cross-reactivity studies of horse, goat and rabbit anti-lymphocyte globulin

In the sera of ten normal humans and twenty-eight candidates for organ transplantation, the passive haemagglutination test detected a 50% incidence of preformed antibodies of low titre directed against horse serum. Such antibodies were also found to cross react with goat or rabbit sera in most instances. Seventeen of the organ recipients were later studied after the institution of treatment with horse antihuman-lymphocyte globulin (ALG). The incidence of anti-horse-serum antibodies rose to 100%. At the same time, an increased activity against goat serum developed; cross-reactions against rabbit serum were also demonstrated but to a less pronounced degree. With immunoelectrophoresis and Ouchterlony diffusion tests, it was shown that the cross-reactivity was to similar although not necessarily identical protein components of the different heterologous sera.