Serum antibodies to LDH-C4.

Human sera from the WHO Reference Bank were tested by a liquid phase radioimmunoassay for antibodies to the sperm-specific form of lactate dehydrogenase (LDH-C4; LDH-X). Modestly elevated levels of antibodies were detected in about 10% of infertile males and females and in about 20% of vasectomized males, as well as in a few cases in other categories. The occurrence of this anti-LDH-C4 activity was without overt correlation with other anti-sperm antibody assays. The primary advantage of the radioimmunometric assay is its absolute specificity for a sperm antigen. These findings lend support to contraceptive vaccine development based on LDH-C4 antigenicity.