Comparative Analysis of the Immunophenotypes of Decidual and Peripheral Blood Large Granular Lymphocytes and T Cells During Early Human Pregnancy

PROBLEM : The functional role of the leukocytes in the decidua is not clear. They may regulate the maternal immune response to the fetal allograft. However, the factors controlling maternal and fetal communication have not yet been identified. METHOD : A comparative analysis of the phenotypes of decidual and peripheral blood large granular lymphocytes (LGLs) and T lymphocytes in early human pregnancy was performed on decidual tissue and blood samples obtained from ten patients at therapeutic abortion. RESULTS : Whereas most of the decidual LGLs were found to have a CD56^bright++ phenotype, most of the peripheral blood NK cells (90%) showed the classical CD56^dim+ phenotype, and only a small proportion were CD56^bright+ cells. Another striking difference was found in the expression of very late antigen 1 (VLA-1, CD49a): Almost all the decidual CD56^bright++ LGLs, but virtually none of the peripheral blood CD56⁺ NK cells expressed this antigen. Further differences were found in the expression of CD16, CD44, CD45RA, CD54, and CD57. There were also differences in phenotype between T cells derived from decidual tissue and those derived from peripheral blood. Approximately 31% of the CD3⁺ decidual T cells expressed VLA-1, but this antigen was virtually absent on peripheral blood T cells. A further difference was seen in the expression of HLA-DR. This activation antigen was found on 32 ± 13% of the decidual T cells but only 8 ± 5% of the peripheral blood T cells. Additionally, the proportion of cells expressing CD38 was higher among decidual than peripheral blood T cells. CONCLUSION : The findings suggest that both decidual LGLs and a subset of decidual T cells are activated and possibly play a role in the control of trophoblast growth and placental development.