Identification of antibody-laden sperm by cytofluorometry*†

A direct assay for measuring sperm-associated immunoglobulin G (IgG) and an indirect assay for measuring IgG plasma antisperm antibodies were devised utilizing fluorescein-labeled antihuman IgG and a fluorescein-activated flow cytometer. The method singularly analyzed Ig attached to the surface of sperm because sperm and nonsperm cells were separately assessed. The direct assay technique results correlated with results from a previously reported direct radiolabeled antiglobulin assay. As few as 100,000 sperm are required in the indirect method; the sensitivity of the indirect technique corresponded with that of a previously reported indirect radiolabeled antiglobulin assay.