Distribution of human leukocyte antigen-ABC and -D/DR antigens in the unfixed human testis

The distribution of the major histocompatibility complex (MHC) antigens in the unfixed human testicle was studied by indirect immunofluorescence. Three murine monoclonal antibodies to the common determinants of class I MHC antigens (human leukocyte antigen [HLA]-ABC) and three against class II MHC antigens (HLA-D/DR antigens), respectively, were utilized. No class I MHC antigens were identified on developing testicular germ cells including spermatozoa, but interstitial cells between the seminiferous tubules (including Leydig cells) and blood vessel endothelium expressed the antigen. Class II MHC antigens were not found on any cells within the seminiferous tubules. However, the class II antigen was identified on dendritic-like cells between the seminiferous tubules and on vessel endothelium, although its expression was expectedly limited. These findings indicate that human testicular germ cells express minimal or no MHC antigens.