Evaluation of human sera for antibodies against sperm by immunofluorescence

Newborn cord sera and sera from pregnant women and from couples with unexplained infertility were observed by indirect immunofluorescence for reactions against human sperm. The sera from the infertile couples had been tested for macro-agglutination and complement-dependent immobilizing antibodies as well. Nonspecific fluorescence was noted only on the quatorial segment. Acrosomes and tail end-pieces were strongly immunofluorescent (positive at a serum dilution of 1:16) with 60 to 70% and 30 to 50%, respectively, of the sera from each main group, with the exception of the nonreactive cord blood. End-piece fluorescence was primarily due to the IgM globulin fraction. It is suggested that cord serum anti-sperm antibodies, directed mainly against the tail main piece, are due to IgG passively acquired from the mother. There was no apparent difference in immunofluorescence between infertile patients and control groups (except for the acrosome and end-piece, with cord sera). However, when the sera from infertile patients were subdivided into groups containing only agglutinating antibody, only immobilizing antibody, and both types of antibody, a higher percentage of the sera from the group having only agglutinating antibody reacted with all sperm areas. This reaction seemed more uniform over the sperm and included the usually negative posnuclear cap and midpiece. The other subgroups showed no obvious trends.