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

(A) 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) OVαβ TCR transgenic double positive (DP) thymocytes have a minimal upregulaton of CD69, which is an indicator of productive TCR-MHC interactions. (C) FACS analysis of lymph node cells shows that, despite poor positive selection, CD4 T cells accumulate in the OVαβ TCR transgenic mouse.