Diverse humoral and cell-mediated effects of antisperm antibodies on reproduction

No single test to detect the presence of antisperm antibodies has correlated precisely with subsequent fertility. The purpose of this study was to determine whether heterogeneous effects of antibodies could potentially explain this observation. The effects of serum on sperm motility, complement-mediated sperm lysis, mouse macrophage-mediated sperm phagocytosis, and sperm IgG opsonization were assessed in several patients with known antisperm antibodies. Each patient's serum produced its own unique profile. Motility ranged from normal (70% to 85%) to 10% using different subjects' serum. Antibody-dependent complement-mediated sperm lysis ranged from 35% to 65%. Normal sperm incubated with normal serum had approximately 200 molecules of IgG per sperm, whereas normal sperm incubated with patient sera had 546 to 900 molecules of IgG per sperm. In all cases where serum enhanced IgG sperm opsonization, there was enhanced mouse macrophage-mediated phagocytosis of the opsonized sperm (a three- to fourfold increase). These data suggest that antisperm antibodies may affect reproduction by different mechanisms, including direct humoral effects (immunoglobulin and/or complement) and indirect cell-mediated effects (macrophage-mediated sperm phagocytosis). However, the mechanism(s) involved are unique to each individual's antibody. The heterogeneity of these potential mechanisms may explain why the presence of antisperm antibodies as measured by a single assay correlate poorly with infertility.