C1q precipitins in human seminal plasma.

Seminal plasma was tested against purified C1q by double diffusion. Precipitation reactions were frequently observed in the seminal plasma of patients with normozoospermia and patients with azoospermia; most of these reactions were not due to soluble immune complexes binding to C1q. A factor resistant to DNAse and RNAse (mol wt: 25,000--150,000 daltons) was found to precipitate C1q. Its discovery adds to the list of substances which may interfere in C1q precipitation tests.