Fetal microchimerism cells suppress arthritis progression by inducing CD14+ IL‐10+ cells in pregnant experimental mice

Background Fetal microchimerism occurs in the mother after a pregnancy. To investigate the role of fetal microchimerism cells (FMCs) in rheumatoid arthritis, we analyzed the population of fetal cells in pregnant experimental arthritis mice. Methods We used EGFP+ fetuses, which were mated with either healthy female mice or CIA mice, and male C57BL/6J‐Tg (Pgk1‐EGFP)03Narl mice, to detect the population of FMCs in maternal circulation. The disease progression was determined by measuring the clinical score and histological stains during pregnancy. The fetal cells have been analyzed if expressing EGFP, CD45, and Scal by flow cytometry. We also detected the expression of CD14+ IL‐10+ cells in vivo and in vitro. Results Our data showed that the pregnancy ameliorated the arthritis progression of CIA mice. The IHC stains showed the CD45 −Sca‐1+ EGFP+ FMCs were expressed in the bone marrow and peripheral blood mononuclear cells (PBMC) at 14 gestation days. However, Treg and Tc cell populations showed no significant change in the bone marrow. The data showed the H2Kb + fetal cells induced CD14+ IL10+ cell populations increased in the bone marrow in vitro and in vivo. Conclusion Our investigations demonstrated that the FMCs protected the CIA mice from cartilage damage and triggered an immunosuppressive response in them by increasing the number of CD14+ IL10+ cells. In conclusion, the FMCs could potentially exhibit protective properties within the context of inflammatory arthritis that arises during pregnancy.