Characterization of a new subset of CD8+HLA-DR+ T cells in human decidua

Abstract

We previously showed that human peripheral blood CD8+HLA-DR+ T cells represent a natural regulatory T cell subset, which acts through cell contact involving CTLA-4. Hereby, our aim was to characterize this T cell subset in first trimester human decidua.CD45+ cells were sorted from elective pregnancy termination tissues (n=8) and stained for surface and intracellular markers. Intracellular staining was performed after PMA stimulation using fixed and permeabilized cells. Flow cytometry analysis revealed that 23±15% of gated lymphocytes were CD3+ cells, among which CD8+ and CD4+ T cell frequencies were 43±13% and 47±16% respectively. Whilst HLA-DR+ cells constituted 42±7% of CD8+ T cells, CD4+Foxp3+ Tregs represented 12.4±6.7% of CD4+ cells. CD8+HLA-DR- cells exhibited a more differentiated CD45RO+CD27-CD28- phenotype (p<0.01) than CD8+HLA-DR+ cells, with a memory-like CD45RO+CD27+CD28+ phenotype (p<0.05). Compared to CD8+HLA-DR-, we observed higher PD-1 (p<0.001) and PD-1/TIM-3 (p<0.05) positivity in CD8+HLA-DR+ T cells, which also expressed higher levels of CXCR3 (p<0.01). CD8+HLA-DR+ cells also showed increased frequency of intracellular (n=5) IL-10 (p<0.001), IFN-γ (p<0.05) and CD107a (p<0.01) positivity than CD8+HLA-DR-.Although additional functional studies are required, we newly identified a subset of memory CD8+HLA-DR+ T cells which could contribute to the tolerogenic capacity of the human decidua acting either through IL-10 secretion or enhanced cytotoxic potential.