Immunological cross-reactivity of mannan-binding proteins in bovine, chicken, and human sera

Immunological cross-reactivity of bovine, chicken and human serum mannan-binding proteins was studied by sandwich enzyme-linked immunosorbent assay. Although some immunological cross-reactivity was observed with whole sera as antigens, almost no cross-reactivity was found with purified mannan-binding proteins. Such cross-reactivity was found to be due to nonspecific reaction since these animal and human sera reacted with preimmune (or normal) rabbit IgG. From these findings, bovine and chicken sera are suggested to contain human rheumatoid factor-like substance(s) reactive with normal rabbit IgG. Thus, it seems to be necessary to compensate nonspecific reactivity of preimmune rabbit IgG with whole sera for determination of crude mannan-binding proteins.