Maternal microchimerism and cell‐mediated immune‐modulation enhance engraftment following semi‐allogenic intrauterine transplantation

Abstract

Successful intrauterine hematopoietic cell transplantation (IUT) for congenital hemoglobinopathies is hampered by maternal alloresponsiveness. We investigate these interactions in semi‐allogenic murine IUT. E14 fetuses (B6 females × BALB/c males) were each treated with 5E+6 maternal (B6) or paternal (BALB/c) bone marrow cells and serially monitored for chimerism (>1% engraftment), trafficked maternal immune cells, and immune responsiveness to donor cells. A total of 41.0% of maternal IUT recipients (mIUT) were chimeras (mean donor chimerism 3.0 ± 1.3%) versus 75.0% of paternal IUT recipients (pIUT, 3.6 ± 1.1%). Chimeras showed higher maternal microchimerism of CD4, CD8, and CD19 than non‐chimeras. These maternal cells showed minimal responsiveness to B6 or BALB/c stimulation. To interrogate tolerance, mIUT were injected postnatally with 5E+6 B6 cells/pup; pIUT received BALB/c cells. IUT‐treated pups showed no changes in trafficked maternal or fetal immune cell levels compared to controls. Donor‐specific IgM and IgG were expressed by 1%‐3% of recipients. mIUT splenocytes showed greater proliferation of regulatory T cells (Treg) upon BALB/c stimulation, while B6 stimulation upregulated the pro‐inflammatory cytokines more than BALB/c. pIUT splenocytes produced identical Treg and cytokine responses to BALB/c and B6 cells, with higher Treg activity and lower pro‐inflammatory cytokine expression upon exposure to BALB/c. In contrast, naïve fetal splenocytes demonstrated greater alloresponsiveness to BALB/c compared to B6 cells. Thus pIUT, associated with increased maternal cell trafficking, modulates fetal Treg, and cytokine responsiveness to donor cells more efficiently than mIUT, resulting in improved engraftment. Paternal donor cells may be considered alternatively to maternal donor cells for intrauterine and postnatal transplantation to induce tolerance and maintain engraftment.

Maternal Dendritic Cells Influence Fetal Allograft Response and Tolerance

“…Unique maternal and recipient TCR/BCR repertoires may serve as therapeutic targets to improve transplantation outcomes. This clinically relevant data, similar to our previous study, 16 supports paternal IUT for clinical trials and encourages short-term maternal immune suppression at IUT.…”

“…In contrast to other reported models using maternal donor cells, 30,31 the model for IUT clinical trial NCT02986698, we observed microchimerism post-mIUT despite reduced MMc, similar to our earlier work. 16 Thus, DCC appears primarily dependent on cell origin, not MMc. We demonstrated that maternal cell trafficking is an active process, the quality of which appears to influence the fetal recipient's immune response to donor cells.…”

“…[11][12][13] Active maternal-fetal trafficking occurs throughout pregnancy, 14,15 increasing after invasive procedures like IUT. [16][17][18] Fetal alloresponsiveness to IUT and subsequent donor cell chimerism (DCC) may be influenced by trafficked maternal cDC. 19,20 To understand how microchimeric maternal immune cells (MMc) in fetal IUT recipients affect DCC , we investigated semi-allogenic and allogenic DCC following transient depletion of maternal cDC subtypes in a murine IUT model.…”

“…Fresh donor bone marrow mononuclear cells (BM-MNC) were prepared as previously described. 16 The day before IUT (E13), CD11c-DTR pregnant mothers (DT+) were given intraperitoneal DT injections (5ng/g body weight). DT-dams received of saline.…”

“…IUT was performed on E14 and all fetuses received intrahepatic injection of 5E+6 donor inoculum, as described previously. 16 Maternal donor cell IUT (mIUT) was performed using B6 BM-MNC (CD45.1, H-2K b ), BALB/c BM-MNC was administered in paternal donor cell IUT (pIUT) and C3H BM-MNC were used for complete allogenic donor cell IUT (aIUT). Uninjected controls were offspring of DT+ or DT-dams which did not undergo intrauterine transplantation.…”