Human decidual tissue contains disarmed CD8+ Effector-Memory T cells (48.2)

Abstract

Abstract During pregnancy maternal lymphocytes at the fetal-maternal interface play a key role in the immune acceptance of the allogeneic fetus. Recently, CD4+CD25bright regulatory T cells have shown to be concentrated in decidual tissue where they are able to suppress fetus-specific immune responses. Decidual CD8+ T cells form the largest fraction of T cells at the fetal-maternal interface but limited data is present on the characteristics of these cells. In this study we examined decidual and peripheral CD8+ T cells for CD45RA, CCR7, CD28 and CD27 expression using nine-colour flowcytometry. Our data demonstrate that decidual CD8+ T cells mainly consist of differentiated CD45RA-CCR7- effector-memory (EM) cells while unprimed CD45RA+CCR7+ naïve cells are absent. Unlike peripheral blood EM T cells, the decidual EM T cells do not express perforin and have a reduced expression of granzyme B, which was confirmed by immunohistochemistry of decidual tissue sections. Interestingly, quantitative PCR shows an increased perforin and granzyme B mRNA content in decidual EM T cells in comparison to peripheral blood. The presence of high levels of perforin and granzyme B mRNA in decidual EM T cells suggests that decidual CD8+ T cells pursue alternative means of EM cell differentiation that may include a blockade of perforin and granzyme B mRNA translation into functional proteins. Regulation of decidual CD8+ T cell differentiation may play a crucial role in maternal immune tolerance to the fetus.