Synchronous deletion of Mtv-superantigen-reactive thymocytes in the CD3(medium/high) CD4(+)CD8(+) subset

Prenatal Allogeneic Tolerance in Mice Remains Stable Despite Potent Viral Immune Activation

Transplanting stem cells before birth offers an unparalleled opportunity to initiate corrective treatment for numerous childhood diseases with minimal or no host conditioning. Although long-term engraftment has been demonstrated following in utero hematopoietic cellular transplantation during immune quiescence, it is unclear if prenatal tolerance becomes unstable with immune activation such as during a viral syndrome. Using a murine model of in utero hematopoietic cellular transplantation, the impact of an infection with lymphocytic choriomeningitis virus on prenatal allospecific tolerance was examined. The findings in this report illustrate that established mechanisms of donor-specific tolerance are strained during potent immune activation. Specifically, a transient reversal in the anergy of alloreactive lymphocytes is seen in parallel with the global immune response toward the virus. However, these changes return to baseline following resolution of the infection. Importantly, prenatal engraftment remains stable during and after immune activation. Collectively, these findings illustrate the robust nature of allospecific tolerance in prenatal mixed chimerism compared with models of postnatal chimerism and provides additional support for the prenatal approach to the treatment of congenital benign cellular disease.

The NOD allele of the Idd5 locus on chromosome 1 mediates a non-cell-autonomous defect in negative selection of T cells

Recent data have suggested that non-obese diabetic (NOD) mice display a defect in negative thymic selection. Using mixed bone marrow chimeras, we demonstrate that the NOD allele of the diabetes susceptibility region 5 (Idd5) locus on chromosome 1, confers defective negative selection in response to endogenous superantigens (SAg) Mtv8 and Mtv9. We generated mixed bone marrow (BM) chimeras in which the donor cells of NOD and C3H or NOD.Idd5(b10) and C3H coexist and are similarly exposed to the Mtv8 and Mtv9 SAg. Under these conditions, SAg-mediated deletion of Vbeta11+ T cells is less efficient in chimeric mice reconstituted with NOD+C3H BM, compared with chimeras reconstituted with NOD.Idd5(b10)+C3H BM. Interestingly, the observed discrepancy was not T cell autonomous but was found to be mediated by a BM derived cellular subset, and under control of a gene(s) in the Idd5 region.