Inhibition of the antibody responses to rat blood transfusion antigens in mice by boar seminal immunosuppressive fraction

PROBLEM: Immunosuppressive fraction of boar seminal vesicle fluid (ISF) was tested to muffle primary and secondary antibody responses to xenotranfusio ns. Contemporaneously, heparin non-binding fraction of seminal plasma (H- f raction), presumed to be identical to ISF, was used to support the results. METHOD: To study their similarity, ISF and H- fraction were analyzed by hig h-performance liquid chromatography and the separated proteins by N-termina l sequencing. In sera of mice treated with ISF or H- fraction, the producti ons of antibodies against rat erythrocytes and blood serum were evaluated b y enzyme-linked immunosorbent assay (ELISA). The productions of IgM, IgA, a nd IgG subclasses were followed by sandwich ELISA. RESULTS: ISF and H- fraction were proved to be equal complexes of porcine s eminal plasma (PSP) proteins PSP I and PSP II. Both inhibited antibody resp onses to rat erythrocytes and serum and the concentrations of IgM, IgG, IgG , and IgG, after the first transfusion with a long-lasting effect. Both sup pressed the secondary antibody production if applied before the second tran sfusion. IgA and IgG, stayed uninfluenced. ISF and H- fraction had an equal immunosuppressive effect. CONCLUSIONS: ISF was characterized biochemically, found to be identical to H- fraction, and determined to be powerful in overcoming unwanted exaggerat ed antibody responses to xenotransfusion.