Prevention of Graft Rejection by Donor Type II CD8⁺ T Cells (Tc2 Cells) Is Not Sufficient to Improve Engraftment in Fetal Transplantation

Abstract

Objectives: Tc2 cells, a subset of CD8⁺ T cells, are able to facilitate engraftment in a murine model of postnatal allogeneic bone marrow transplantation. The purpose of this study was to evaluate whether Tc2 cells could improve engraftment in fetal transplantation. Methods: Gestational day 13 C57BL/6 (H-2^b) fetal mice were used as recipients, adult B6D2F₁ mice (C57BL/6 × DBA/2, H-2^b/d) as donors, and splenocytes from B6C3F₁ (C57BL/6 × C3H/He, H-2^b/k) mice were used as stimulators in cultures used to generate the Tc2 cells from B6D2F₁ mice. Peripheral blood chimerism was examined monthly for 3 months. Thereafter, recipients were sacrificed to evaluate the levels of peritoneal, splenic and bone marrow chimerism. The T-cell responses of recipient splenocytes to cells of host origin were measured as a proliferative response in mixed lymphocyte cultures. Results: Low levels of peripheral blood cell chimerism (<0.3%) were observed at 1 month of age, which declined further by 3 months of age. The levels of donor cells in the spleen, bone marrow and peritoneal cavity were usually not more than 0.05%. The peritoneal cavity tended to have higher levels of donor cells with 1 recipient sustaining as high as 25.03% at the age of 3 months. Higher peritoneal chimerism correlated with a lower donor-specific T-cell response. Conclusions: Transplantation of Tc2 cells was insufficient to improve bone marrow engraftment in utero, suggesting that graft rejection is not the major barrier to successful in utero transplantation. Donor cells can persist in the peritoneal cavity and might play an important role in inducing immune tolerance in fetuses.

Prenatal Tolerance Induction: Relationship between Cell Dose, Marrow T-Cells, Chimerism, and Tolerance

“…LDBMCs (groups I-IV) or TDBMCs (group V) were injected IP in 5-10 µl cells can facilitate engraftment at the expense of graftversus-host disease (GVHD) (29). This "double-edged phosphate-buffered saline (PBS) into gestational day 14 fetuses as previously described (9,10). The pregnant sword" phenomenon has also been observed in IUT models in mice, sheep, and primates (3,12,22,36) that mice were housed in an undisturbed room without bedding changes until the pups were 1 week old.…”

“…Adult light-density BMCs (LDBMCs) from C57BL/ Skin transplantation was performed, using tail skin grafts from FVB/N (syngeneic), C57BL/6 (donor-6 mice (8-24 weeks old) were prepared by density gradient centrifugation as previously described (9,10). Tspecific), and BALB/C (third-party) mice.…”

“…As for recipients with donor cells of <10% at 1 cell installation. In fact, peritoneal donor cells, mostly composed of B and myeloid cells (10), can persist at month old, transient chimerism (<2%) only led to donor-FACING PAGE Figure 4. Donor cell levels of durable and transient low-level chimeras, the survival curves of donor-specific skin grafts, and accepted skin grafts.…”

Cellular therapies supplement: the peritoneum as an ectopic site of hematopoiesis following in utero transplantation

“…We were surprised when we examined cells recovered from the peritoneal cavity of mice that had been transplanted in utero with haplogeneic cells (H-2 b/d B6D2F1 donor cells into H-2 b C57BL/6 recipients) to discover that in some 3-to 5-month-old recipients, donor cells represented as much as 25% of all recovered cells. 14,15 Although in most animals the levels of chimerism were Յ1%, the frequency of donor cells in the peritoneum was higher than in the marrow, peripheral blood, or spleen. The peritoneal cells consisted of B cells, T cells, F4/80-antigen + macrophages, and Gr1 + myeloid cells.…”

“…Our initial observations using the haplogeneic mouse transplant model (H-2 b/d into H-2 b ) demonstrated a correlation between peritoneal chimerism and T-cell tolerance. 14,15 MLRs were performed 3-5 months after IUT, and responses were categorized as normal responsiveness (relative to third-party allogeneic stimulator cells), hyperresponsiveness, or hyporesponsiveness. Donor chimerism in the marrow, blood, and spleen in this set of transplants was low (<1%) or absent.…”