Detection of sperm surface related antibodies by indirect immunofluorescence test on sperm suspensions. Indirect IFT on sperm suspensions

An indirect immunofluorescence test (IIFT) using sperm suspensions was carried out on 20 sera with sperm agglutinins (SA) and on 25 negative controls. IIFT gave results highly correlated with the occurrence of sperm agglutinating activity. Moreover, a relation was found among class of Ig involved in IF reactivity, fluorescent stain pattern and type of sperm agglutinations. In all sera with "mixed" or "tail-tail" sperm agglutinating activity, IgG were involved in IF reactivity; the fluorescent stain constantly appeared in a granular pattern along the sperm tail and most often on the head surface too. In relation to high titres of "head-head" sperm agglutinating activity, IgM were involved in IF reactivity; here the fluorescent stain appeared to be localized on acrosomal surface. The results indicate that indirect IFT on sperm suspensions specifically detects sperm surface related antibodies.