passages.id: split_1_test_3113_passage
passages.type: progene_text
passages.text: Human leukocyte antigen - G ( HLA-G ) has long been speculated as a beneficial factor for a successful pregnancy for its restricted expression on fetal - maternal extravillous cytotrophoblasts and its capability of modulating uterine natural killer cell ( uNK ) function such as cytotoxicity and cytokine production through NK cell receptors .