PROBLEM: The T-cell antigen receptor (TCR) has been reported to be down-regulated on T-cells in the decidualized endometrium in early pregnancy.
METHOD OF STUDY: The expression of CD3ζ, a component of the TCR complex, has been investigated in human first-trimester decidual T-cells using flow cytometric analysis of permeabilized cells.
RESULTS: Levels of CD3ζ expression were significantly lower in decidual than in peripheral T-cells from non-pregnant women, as assessed by mean fluorescence intensity (4.2 vs. 5.5. logarithmic scale, P < 0.05). However, when decidual and peripheral T-cells from the same subjects were analyzed (n = 10), mean levels of CD3ζ were slightly, but not significantly, lower in decidual than in peripheral T-cells (P > 0.1). CD3ζ was not substantially down-regulated systemically as mean cytoplasmic CD3ζ levels did not differ significantly between peripheral blood T-cells from pregnant women and non-pregnant controls (P > 0.2). CD8+ cells outnumber CD4+ cells in decidua, but neither the proportions of these two T-cell subsets positive for cytoplasmic CD3ζ nor the mean levels of CD3ζ were significantly different.
CONCLUSIONS: These results indicate that human decidual T-cells do not greatly down-regulate CD3ζ, but it is unclear if a small decrease in mean levels may be sufficient to compromise their capacity for activation.