SPACA3 is a 215 amino acid protein that participates in the fusion and adhesion of sperm and egg plasma membrane during fertilization. Identified as a novel cancer/testis antigen in hematologic malignancies, SPACA3 has the ability to elicit B-cell immune responses in patients with cancer and is considered a potential target for immunotherapy. A member of the glycosyl hydrolase 22 family which is expressed in testis, placenta and epididymis, SPACA3 exists as two alternatively spliced isoforms; SPACA3 isoform 1 is a single-pass type II membrane protein of the sperm acrosome whereas SPACA3 isoform 2 is a secreted protein.