Major histocompatibility complex expression on human, male germ cells: a review.
OBJECTIVE
The male reproductive compartment is an immunologically privileged site. The expression pattern of human leukocyte antigens (HLAs) may play an important role in the maintenance of immune tolerance toward differentiating gametogenic cells. This review presents current knowledge about HLA gene expression on human, male germ cells, on mRNA and protein levels, and on their methylation status.


METHODS
Different techniques were applied to study HLA gene expression in human testis: (a) protein: e.g., cytotoxicity test, fluorescent labeling techniques, enzyme-linked immunosorbent assay, and confocal microscopy; (b) mRNA: reverse transcriptase-polymerase chain reaction, Northern blot hybridization, and in situ hybridization; and (c) methylation status.


RESULTS
In normal testicular tissue we observe a lack of HLA-class I (classical) antigens expression and inversely related expression pattern of HLA class I classical and nonclassical genes. HLA-A, -B, -C, and -E loci are likewise methylated in somatic and germ cells, whereas -F and -G genes are less methylated in sperm precursors.


CONCLUSIONS
Immunologic tolerance in human testis is actively maintained by the specific expression pattern of HLA genes regulated by hormones and growth factors.
Fiszer
D
D
Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland.
Kurpisz
M
M
D015870:Gene Expression; D006680:HLA Antigens / Q000096:biosynthesis* / Q000276:immunology; D006801:Humans; D008297:Male; D013094:Spermatozoa / Q000276:immunology / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000276:immunology / Q000378:metabolism
D006680:HLA Antigens