A Th2 chemokine, TARC, produced by trophoblasts and endometrial gland cells, regulates the infiltration of CCR4⁺ T lymphocytes into human decidua at early pregnancy

Problem: A chemokine receptor, CCR4 preferentially expressed on type 2 helper T (Th2-type) cells, and its ligand, thymus and activation regulated chemokine - (TARC/CCL)- play important roles in the recruitment of Th2-type cells. We examined the distribution of CCR4 expressing CD4⁺ and CD8⁺-T cells in human decidua at early pregnancy, and localized TARC in the decidual tissue and chorionic tissue. Method of study: Decidual tissue was obtained by legal abortion. The percentages of CCR4 expressing CD⁺ and CD8⁺-T cells were analyzed by flow cytometry. Localization of TARC protein was evaluated by immunofluorescence staining. The expression of TARC mRNA in the choriocarcinoma cell line and endometrial cell line was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). Result: The percentages of CCR4⁺ cells in CD4⁺-T cells and CD8⁺-T cells were significantly increased in human early pregnancy decidua compared with those in peripheral blood. An another marker of human Th2 and Tc2 cells, CRTH2 molecules was also expressed on CCR4⁺ CD4⁺-T cells and CCR4⁺ CD8⁺-T cells. In addition, we found that trophoblasts, uterine epithelial cells and endometrial gland cells produce TARC by immunohistochemical staining and the RT-PCR method. Conclusion: Our findings imply that TARC secreted in decidua mediates the infiltration of CCR4⁺ T-cell migration into the fetomaternal interface, decidua, resulting in the maintenance of pregnancy.