Decidua as a Site of Extrathymic VγI T-cell Differentiation

Abstract

PROBLEM: 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⁻ CD56^bright large granular lymphocytes. METHODS: In this study we analyzed expression of TCR Vγδ gene segments in peripheral lymphocytes and decidual and nonpregnant endometrial samples using RT‐PCR and oligonucleotide hybridization. RESULTS: Interestingly, a limited repertoire of Vγ gene segments were discovered in decidual lymphocytes of normal pregnancy when compared with peripheral lymphocytes, whereas usage of Vδ gene segments were ubiquitous in peripheral and decidual lymphocytes. Strong expression of VγI gene segment, often exceeding 50% of total Vγ, were noted in all (13/13) pregnant decidual tissues obtained at different gestational stages. Interestingly, this predominance of VγI gene is also noted in nonpregnant endometrial samples and the decidua of patients with ectopic pregnancies. CONCLUSIONS: Our results suggest the nature of decidual VγI T cells as possible suppressors of rejective maternal cytotoxic T cells during the maintenance of normal pregnancies.