Major histocompatibility antigens are not expressed on human epididymal sperm.

Abstract

Evidence for expression of major histocompatibility antigens in reproductive tissues (i.e., the placenta and gametes) has been conflicting ( 1 , 2). Several investigators reported haploid expression of both Class I (HLA-A, B, C) and Class II (HLA-DR) major histocompatibility complex (MHC)3 products on human ejaculate sperm (3-5). Other recent studies, however, failed to detect HLA antigens on sperm (6-8) and the following concerns have been raised: 1 ) detection of HLA by quantitative absorption or cellular assays may be due to somatic cell contaminants; 2) the standard HLA typing allosera used in many of these studies is obtained from multiparous women and may contain "extra" antibodies directed against other embryonic antigens expressed on sperm; and 3) seminal plasma contains HLA molecules that are passively absorbed onto sperm (7). In this study we circumvented these concerns by using a panel of highly specific monoclonal antibodies with well-defined reactivity against antigenic determinants on HLA Class I and Class II molecules, a combination of sensitive radioimmunoassay and histologic techniques, and both epididymal and ejaculate human sperm.