Investigation of sperm receptors in the hamster zona pellucida by using univalent (Fab) antibodies to hamster ovary.

An antiserum raised in rabbits against hamster ovaries was digested with papain to obtain the univalent (Fab) fragments. The anti-zona pellucida activity of this preparation was monitored by a direct fluorescence test and by an indirect precipitation test. In contrast to the effects produced by immune gamma-globins on the zona pellucida, the immune Fab antibodies failed to form a precipitate layer on the zona pellucida and did not inhibit fertilization in vitro. Immune Fab antibodies also failed to overcome the fertilization-inhibiting effects of zona sperma receptors in solution. It is concluded that the sperm receptors, which are thought to be essential for sperm attachment to the zona pellucida and consequently for fertilization, have little or no antigenicity.