Figure 1. Events at egg fertilization and the possible roles of ß-defensin proteins in regulating this process.

Sperm capacitation is required for egg fertilization and involves several cellular changes including loss of cholesterol from the sperm head and increased membrane hyperpolarization. ß-defensin proteins may inhibit these events to help prevent premature sperm capacitation. In addition, ß-defensins might also block Ca²⁺ entry, which is required for the acrosome reaction.