Cytotoxic antibodies to lymphocytes: relationship to sperm immunity

Sperm and T lymphocytes share antigens, and sera from infertile subjects with sperm immunity have agglutinating antibodies to T lymphocytes. In the present study, cytotoxic antibody titers to sperm (C-Sp) and lymphocytes (C-Ly) were measured in sera, seminal plasma, cervical mucus and vaginal secretions of 52 infertile couples. The samples were divided into C-Sp negative and C-Sp positive groups. C-Ly titers against control T lymphocytes were significantly elevated in C-Sp positive sera of 35 males (P less than 0.005) and 27 females (P less than 0.05) as compared with C-Sp negative sera. C-Ly titers against autologous or partner T lymphocytes were similarly elevated in the sera of both groups. Titers of C-Ly in C-Sp positive secretions (seminal plasma, cervical mucus and vaginal secretions) against autologous and partner, as well as control, T lymphocytes were significantly elevated. In addition, elevated titers of C-Ly to autologous, partner and control B lymphocytes were observed in sera, cervical mucus and vaginal secretions from females with sperm immunity. The infertile males, however, did not have significant B lymphocyte immunity. Immunofluorescence assays revealed a significantly higher incidence of sperm and T lymphocyte antibodies (primarily IgG) in the C-Sp positive than in the C-Sp negative group. Titration of 100 sera from infertile subjects (50 couples) against a panel of lymphocytes of known HLA specificities failed to reveal a pattern of activity against HLA antigens of the A, B and C loci. Absorption of immune sera with sperm or lymphocytes reduced C-Sp and C-Ly titers significantly (P less than 0.001). These results suggest that infertile subjects with sperm immunity produce antibodies to cross-reactive antigens present on sperm and T lymphocytes.