Thymocytes expressing the OVαβ TCR are poorly positively selected even in the absence of endogenous TCRs.

<p>(<b>A</b>) As compared to thymocytes expressing the high affinity MPBαβ TCR, the OVαβ TCR is very inefficiently positively selected, which is reflected in a much lower percentage of CD4SP thymocytes. (<b>B</b>) OVαβ TCR transgenic double positive (DP) thymocytes have a minimal upregulaton of CD69, which is an indicator of productive TCR-MHC interactions. (<b>C</b>) FACS analysis of lymph node cells shows that, despite poor positive selection, CD4 T cells accumulate in the OVαβ TCR transgenic mouse.