THE EXPRESSION OF HLA-G ANTIGEN IN DIFFERENT HUMAN TISSUES AND PLACENTAS AT DIFFERENT STAGES OF PREGNANCY

Abstract

The distribution of HLA-G antigens in human tissues including placents was examined by immunohistochemical methods, using monoclonal antibody (Mab) specific to HLA-G antigen (87 G). Comparatively, class Ⅰ specific Mab, W 6/32 was also employed for the detection of the antigen. W 6/32 reacted with a wide variety of cells and tissues throughout the body, whereas Mab 87 G did not react at all with these W 6/32 reactive cells except for those of placental tissues. Mab 87 G reacted with extravillous cytotrophoblast cells such as cytotrophoblastic cell columns, cytotrophoblastic shell and invasive cytotrophoblast but not other parts of placentas throughout the pregnant periods. Essentially the same results were obtained with W 6/32 staining in placentas. These results indicate that HLA-G antigens are exclusively expressed in extravillous cytotrophoblast cells although we cannot rule out the possibility that undetectable amounts of the HLA-G antigen or its isoforms which cannot be recognized by the Mabs used in this study are synthesized in some other tissues.