IMMUNOGLOBULINS FROM HUMAN FOLLICULAR-FLUID INDUCE THE ACROSOME REACTION IN HUMAN SPERM

The ability of human follicular fluid (hFF), retrieved from women unde rgoing IVF to induce the acrosome reaction (AR) in human sperm has bee n documented by several laboratories. However, the nature of the activ e factors in the hFF and the physiological meaning of the AR induction are highly controversial. We performed a three step purification sche me for hFF and all the fractions were screened for the AR-inducing act ivity. AR activity was associated with a protein fraction of M(r) > 18 0 kD that on further analysis under PAGE was found to be composed by s ubunits of apparent M(r) 50,000 and 29,000. The N-terminal sequences o f these bands showed a 100% homology with the heavy and light chains o f human IgG. A polyclonal antibody raised against the purified protein and anti-human IgG were both able to suppress the acrosome reaction-i nducing activity of crude hFF. However, neither normal human serum nor a purified preparation of human IgG were able to mimic the AR-inducin g activity of hFF. We concluded that the AR-inducing activity of hFF i s, at least in part, due to the presence of antisperm antibodies. (C) 1994 Wiley-Liss, Inc.