• Pregnancy immunology;
  • immunology of decidua;
  • cell traffic;
  • suppressor cells

ABSTRACT: Recent studies of the surface markers on cells in murine decidua have suggested that a proportion of the cells originate from the bone marrow. To examine directly the migration of bone marrow cells to decidua, we labeled whole bone marrow with TRITC and counted the number of cells appearing in decidua following adoptive transfer to virgin or allopregnant C3H mice. Labeled cells were readily identified in decidua by 3 hours after injection, and fewer cells were seen in the lining of the virgin uterus compared to allopregnant recipients. The presence of labeled cells could not be explained by blood contamination. The TRITC-labeled cells were found preferentially at the implantation sites, and while labeled bone marrow cells could be found in spleen as well as in decidua, adoptively transferred TRITC-labeled spleen cells localized preferentially in spleen and lymph nodes draining the uterus rather than in decidua. Velocity sedimentation analysis showed that the labeled bone marrow cells lodging in decidua were small lymphocytic cells (S = 2.5–4 mm/hr) and appeared to derive preferentially from small-sized bone marrow cells (S < 4.3 mm/hr). These observations indicate that a subpopulation of bone marrow cells selectively homes to the implantation site in decidua during successful allopregnancy. The possible significance of this observation is discussed.