Differential diagnosis of immature germ cells in semen utilizing monoclonal antibody MHS-10 to the intra-acrosomal antigen SP-10.

The monoclonal antibody (mAb) MHS-10 (IgG1) is a mouse antihuman sperm antibody which recognizes a polymorphic sperm protein, (SP-10), which has previously been localized within the acrosomal matrix and the acrosomal membranes. The SP-10 antigen has been shown to be sperm-specific and is not found in somatic tissues. It is stage specific, having been immunohistologically localized to Golgi phase spermatids and all subsequent phases of spermiogenesis. In the present study, acetone-dried smears from washed human semen containing significant numbers of round cells were probed with mAb MHS-10. Monoclonal antibody-labeled cells were visualized by a standard streptavidin-biotin immunoperoxidase method using a light microscope. The MHS-10 mAb immunoreacted with mature sperm and with a subset of round cells diagnosed as developing spermatids, which had been sloughed off from the testis at varying stages of acrosome formation. To rule out possible cross-reactivity of the mAb with leukocytes in semen, a leukocyte surface marker (anti-HLe-1) was used in conjunction with MHS-10. Round cell populations staining with MHS-10 did not stain with anti-HLe-1. The mAb MHS-10 is thus a promising probe for the identification and quantitation of immature germ cells in human semen.