Abstract
SPAG11 (sperm associated antigen 11) is a family of proteins that have a specific domain designated "Sperm antigen HE2" and some isoforms also have a domain of ²-defensin. These proteins are abundantly expressed in the male reproductive tract, particularly in the epididymis. SPAG11 proteins have antimicrobial activity, as well as being involved in sperm maturation, capacitation, sperm su…