A study of human leukocyte antigen G expression in hydatidiform moles

OBJECTIVE: Human leukocyte antigen G (HLA-G) is a nonclassic major histocom patibility gene normally expressed only in extravillous trophoblasts throug hout pregnancy. It may be responsible in part for the successful evasion of the hemiallogenic trophoblasts from maternal immune surveillance. We inves tigated whether HLA-G is expressed in molar pregnancies. STUDY DESIGN: We examined 5 complete hydatidiform mole specimens and 5 part ial hydatidiform mole specimens to determine whether HLA-G is expressed by immunohistochemistry and by RNA in situ hybridization analysis. RESULTS: We found that both the protein and RNA of HLA-G is expressed in co mplete and partial hydatidiform moles. CONCLUSION: HLA-G RNA and protein are expressed in molar pregnancies. HLA-G expression is independent of embryonic development and may therefore be an integral part of placental development. Furthermore, expression of HLA-G i n the complete hydatidiform mole, a naturally occurring androgenote, confir ms expression of the paternal allele of HLA-G. Imprinting of HLA-G is there fore unlikely to play a role in protecting fetal trophoblasts from maternal immune rejection.