Enumeration and characterization of self-reactive T cells in polyclonal populations (111.25)

Abstract

Abstract The thymic processes of positive and negative selection are crucial for the formation of a functional T cell repertoire. TCR transgenic models have provided crucial insight into these processes, but it has not been possible to quantitate positive and negative selection in normal diverse polyclonal populations. We developed a Nur77GFP transgenic reporter mouse that specifically expresses GFP in T cells in response to TCR stimulation. Using Nur77GFP mice crossed to mice deficient in the pro-apoptotic molecule Bim, we found that two times more DP thymocytes are negatively selected by high affinity interactions than are positively selected by low affinity interactions. We also identified the fraction of SP thymocytes undergoing further deletion in the medulla, after positive selection. Cells that are rescued from negative selection have increased Nur77GFP compared to foxP3+ T regulatory cells, suggesting that T cells undergoing negative selection have TCRs with higher affinity for self compared to developing T regulatory cells. Finally, our results identify a population of self-reactive CD25-CD44+ CD4 T cells in mesenteric LNs, which have a phenotype consistent with clonal anergy. Future studies using this model will allow us to identify and quantitate selection defects in various mutant or autoimmune prone animals.