Human leukocyte antigen F protein is expressed in the extra-villous trophoblasts but not on the cell surface of them.

PROBLEM: Human leukocyte antigen (HLA)-F together with other class 1b HLAs may play a pivotal role in immunological interaction at feto-maternal interface. However, it is not elucidated whether HLA-F is expressed on cell surface of extra-villous trophoblasts (EVTs). METHOD OF STUDY: The localization of HLA-F in placenta of each trimester was investigated by immunohistochemistry. The expression modality of HLA-F molecule was compared with that of HLA-G in cultured EVTs using flowcytometry. RESULTS AND
CONCLUSION: In immunohistochemical study, remarkable staining for HLA-F was confirmed in EVTs throughout gestation. HLA-F expression was restricted to be intracellular in cultured EVTs. HLA-F expression was increased with time in culture, which was accompanied by the increase of cell surface HLA-G. Consequently, HLA-F lacking in cell surface expression on EVTs may not contribute to the direct cell-to-cell immune reaction but might work supportively modifying the function of HLA-G.