Monoclonal antibodies identify Fc gamma receptors on unfertilized human oocytes but not spermatozoa.

Oolemmal Fc receptors have previously been shown to play a role in the promotion of adhesion by antibody labeled human spermatozoa to zona-free hamster eggs. In this work, we demonstrated the presence of Fc gamma RI, Fc gamma RII and Fc gamma RIII on the oolemma of unfertilized human oocytes by means of monoclonal antibodies directed against these receptors, detected both by immunobead rosetting and indirect immunofluorescence. These receptors were also functionally active in that they were able to bind human aggregated IgG, human IgG-Fc, mouse IgG1 and IgG2a. While the presence of oolemmal IgG-Fc receptors might play a role in reproductive failure, by their promotion of polyspermic fertilization, in cases where antisperm antibodies bound to the spermatozoan surface, their role in the normal physiology of fertilization or in other events unrelated to sperm incorporation remains to be determined. In contrast, Fc gamma receptors were not present on human spermatozoa, irrespective of their functional state (fresh ejaculated, capacitated or acrosome reacted).