Human epididymal secreted protein CD52 on ejaculated spermatozoa: correlations with semen characteristics and the effect of its antibody

Abstract

CD52 is a glycosylphosphatidylinositol-anchored glycoprotein secreted by the epididymis where it is incorporated into sperm membranes. The antigen is common to spermatozoa and lymphocytes, and its role is not known. Quantitative analysis using immunostaining with the monoclonal antibody CAMPATH-1G and flow cytometry indicated positive signals from approximately 80% of viable, washed ejaculated spermatozoa. Staining intensity increased after capacitation overnight, and decreased after short incubation with high density lipoprotein. After incubation of Percoll-washed spermatozoa with CAMPATH-1G, motility was reduced from 83 to 74% after 5 min and from 73 to 52% after 3.5 h. Swimming velocities were reduced by approximately 30% and linearity by 15% in 5 min, but no further decreases were observed over 3.5 h. After 20 min incubation with the antibody, cell viability was decreased by 10 and 20% in freshly washed and capacitated spermatozoa respectively. Comparison of fertile and infertile patients revealed no difference in the percentages of immunostained spermatozoa or in staining intensity and there were no differences in sperm labelling between normozoospermia and teratozoospermia. Compared with normozoospermia, percentages of stained spermatozoa were lower by 20 and 27% in asthenozoospermia and oligozoospermia respectively, whereas staining intensity in asthenozoospermia was less than half that in oligozoospermia. The correlation of percentages of stained spermatozoa with percentages of motile cells suggests the involvement of epididymal CD52 in the maturation of sperm function.