The mechanism of spontaneous sperm agglutination in the ejaculate of a subfertile man was investigated. Using enzyme-linked immunosorbent assays it was found that the patient's spermatozoa had a mean of 2.3 times more IgA bound to it than did spermatozoa from fertile men. IgA antibody to spermatozoa was also found in the patient's seminal fluid and prostatic fluid, but not in his serum. In this patient it appeared that agglutination was due to an IgA antibody to spermatozoa that was produced locally within the genital tract.
Witkin SS, Zelikovsky G, Bongiovanni AM, Good RA, Day NK. IgA Antibody to Spermatozoa in Seminal and Prostatic Fluids of a Subfertile Man. JAMA. 1982;247(7):1014-1015. doi:10.1001/jama.1982.03320320050030