Quantification of C3 and C4 in infertile men with antisperm antibody in their seminal plasma

Previous studies showed that some infertilities are caused by antisperm antibodies (ASAs). It was shown that some major complement (C) components are present in seminal fluid. Due to the role of C in the pathogenesis of ASAs, the existence and amount of two key C components (C3 and C4) were investigated in seminal plasma (SP).

Single radial immunodiffusion assay and a sandwich-type enzyme-linked immunosorbent assay (ELISA) were used for C3 and/or C4 quantification, respectively, in serum and SP, and the tray agglutination test was used for ASA detection in 12 fertile and 53 infertile men (18 ASA-positive [ASA+] and 35 ASA-negative [ASA-] men).

Of the 18 ASA + infertile men, 61.11% had positive C3, whereas 27.77% showed positive C4 levels. ASA + infertile men showed significant differences in seminal plasma C3 mean values compared with ASA- infertile (P < 0.01) and fertile (P < 0.05) men, but the seminal plasma C4 values only showed differences compared with ASA- infertile men (P < 0.05). No significant differences were observed in serum C3 and/or C4 levels of ASA+ infertile men compared with other groups. No significant correlation was found between ASA titer and C3 and C4 levels in SP. A significant correlation existed between SP and serum C3 levels of ASA+ (r = 0.522, P < 0.01) and ASA- (r = 0.451, P < 0.01) infertile men, but no correlation was observed between C4 levels.

In the presence of ASAs, the C system has no definitive activity in blood serum or outside the male genital tract. In SP, and in association with ASAs, C has no lytic activity by the classical pathway. The excess of C3 in SP of ASA+ infertile men may participate in other C-mediated activities in the male reproductive tract.