Decidua as a site of extrathymic V gamma I T-cell differentiation.

Abstract

Decidual tissue is an interface between the host and fetus, which is regarded as a natural allograft. We have reported the possible presence of extrathymic T cells in human decidua through the expression of recombinase-activating genes in the decidual CD16-CD56bright large granular lymphocytes. In this study we analyzed expression of TCR V gamma delta gene segments in peripheral lymphocytes and decidual and nonpregnant endometrial samples using RT-PCR and oligonucleotide hybridization. Interestingly, a limited repertoire of V gamma gene segments were discovered in decidual lymphocytes of normal pregnancy when compared with peripheral lymphocytes, whereas usage of V delta gene segments were ubiquitous in peripheral and decidual lymphocytes. Strong expression of V gamma I gene segment, often exceeding 50% of total V gamma, were noted in all (13/13) pregnant decidual tissues obtained at different gestational stages. Interestingly, this predominance of V gamma I gene is also noted in nonpregnant endometrial samples and the decidua of patients with ectopic pregnancies. Our results suggest the nature of decidual V gamma I T cells as possible suppressors of rejective maternal cytotoxic T cells during the maintenance of normal pregnancies.