Immunoregulatory properties of decidua macrophages

Abstract

About 15–20% of bone marrow derived cells in the endometrium and the decidua are CD14‐positive macrophages coexpressing the scavenger receptor CD163. The costimulatory molecule CD86 (B7‐2) but not CD80 (B7‐1) is found expressed on first trimester and term decidua macrophages (D‐Mph). The number of D‐Mph increases at the implantation site in the basal decidua, where they are in contact with the HLA‐G‐positive invading extravillous cytotrophoblast. As D‐Mph express the inhibitory receptors CD85d (ILT4, LIR‐2) and CD85e (ILT2, LIR‐1), they are potentially susceptible to inhibition by class Ia and class Ib molecules. D‐Mph may have specific functions relating to successful pregnancy, and phenotypic and functional properties may differ between early and term pregnancy. A number of data make their molecular repertoire comparable to those of alternatively activated macrophages which are immunosuppressive. For instance, first trimester decidua macrophages express IL‐10 and the MS‐1 high molecular weight antigen on the cell surface fibronectin and F XIIIa are detectable. Functional data are required to complement these studies.