CD33(+) /HLA-DR(neg) and CD33(+) /HLA-DR(+/-) Cells: Rare Populations in the Human Decidua with Characteristics of MDSC.

Problem Human pregnancy needs a remarkable local immune tolerance toward the conceptus. Myeloid-derived suppressor cells (MDSC) are important players promoting cancer initiation and progression by suppressing T-cell functions and thus inducing immune tolerance. Therefore, MDSC were expected within decidua. Methods Subpopulations of CD33+ immune cells were isolated from human early pregnancy decidua and characterized phenotypically and functionally by microscopy, FACS analysis, RT-PCR, Western blotting and in the coculture with T cells. Results Decidua harbors CD33+/HLA-DRneg and CD33+/HLA-DR+/− cells which both express arginase, iNOS and IDO and a typical cytokine profile. Both subtypes potently suppress T-cell proliferation and therefore fulfill the criteria of MDSC. Conclusion We characterized a new population of CD33+/HLA-DRneg and CD33+/HLA-DR+/− cells in human early pregnancy decidua with properties of classical MDSC and thus potentially being an important player in immune tolerance in pregnancy.