Viral Infection: A Potent Barrier to Transplantation Tolerance

Figure 5

Heterologous immunity; cross-reactivity between viral and allogeneic antigens. Unlike the very small proportion of naive T cells that can respond to any given pathogen (reported to be ~1:200 000), the frequency of T cells that directly recognize allogeneic antigens, such as MHC, is thought to be within 1:100–1:10. A proportion of those TCRs that recognize alloantigens, therefore, may have arisen as a result of virus infection that induces virus-specific T cells that cross-react with allo-MHC. Activation of these T cells may result in the recognition of MHC molecules found on donor tissues, such as the endothelium of transplanted organs, precipitating allograft rejection.