Do human eggs attract spermatozoa?

A key process in human fertilization is bringing the two gametes together, so that the complex molecular events involved in sperm and egg interaction can begin. Does nature allow fertilization to occur only as a consequence o f a chance collision, or is there a precontact sperm-egg communication? Thi s review summarizes the bioassays used in testing human spermatozoa for che motaxis, emphasizing the necessity to distinguish between chemotaxis and ot her accumulation-causing processes, and the results obtained. It demonstrat es that human sperm chemotaxis to a follicular factor(s) does occur, at lea st in vitro, and that only capacitated spermatozoa are chemotactically resp onsive. Substances that have been proposed as attractants for human spermat ozoa are reassessed. The potential role of sperm chemotaxis in vivo is disc ussed. Faulty precontact sperm-egg communication may be one of the causes o f male infertility, female infertility, or both. On the other hand, interfe ring with human sperm chemotaxis may represent an exciting new approach to contraception. BioEssays 21:203-210, 1999. (C) 1999 John Wiley & Sons, Inc.