Problem: Immunosuppressive fraction of boar seminal vesicle fluid (ISF) was tested to muffle primary and secondary antibody responses to xenotranfusions. Contemporaneously, heparin non-binding fraction of seminal plasma (H- fraction), presumed to be identical to ISF, was used to support the results.
Method: To study their similarity, ISF and H- fraction were analyzed by high-performance liquid chromatography and the separated proteins by N-terminal sequencing. In sera of mice treated with ISF or H- fraction, the productions of antibodies against rat erythrocytes and blood serum were evaluated by enzyme-linked immunosorbent assay (ELISA). The productions of IgM, IgA, and IgG subclasses were followed by sandwich ELISA.
Results: ISF and H- fraction were proved to be equal complexes of porcine seminal plasma (PSP) proteins PSP I and PSP II. Both inhibited antibody responses to rat erythrocytes and serum and the concentrations of IgM, IgG, IgG1 and IgG2 after the first transfusion with a long-lasting effect. Both suppressed the secondary antibody production if applied before the second transfusion. IgA and IgG3 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 exaggerated antibody responses to xenotransfusion.