The age-related changes in the incidence of 'natural' anti-sperm antibodies suggest they are not auto-/isoantibodies.

Problem: Establishing the age-dependent patterns of sperm antibody levels among normal humans.

Methods Of Study: Sera samples from 498 healthy subjects aged 0-97 years - 246 males and 252 females - were tested by the gelatin agglutination test of Kibrick, tray agglutination test of Friberg, sperm immobilization test of Isojima and enzyme-linked immunosorbent assay (ELISA).

Results: We found a significant increase in the level of sperm agglutinins after 40 years, which decreased after 88 years.