Description
These studies utilized two TCR transgenic mouse lines, LLO118 and LLO56, that our laboratory has developed and characterized, which recognize the same Listeria monocytogenes LLO/IO-Ab epitope with equal affinities. When 104 naive CD4+ LLO T cells are transferred into a B6 mouse and one day later infected with wild type Listeria monocytogenes, the LLO118 T cells have a more robust primary expansion than LLO56. In contrast, after a secondary challenge, LLO56 T cells have a much greater expansion than LLO118 T cells. One striking phenotypic difference between the LLO118 and LLO56 T cells lies in their CD5 expression. CD5 expression has been shown to correlate directly with TCR affinity for self-pMHC and tonic signaling. LLO56 cells have a higher basal phosphorylation of the TCR chain, and they have significantly increased expression of Nur77 mRNA. These transcriptional profiling experiments examined if there were transcriptional differences between LLO118 and LLO56 T cells, either naive or after D7 of infection, that would account for their disparate in vivo behaviors.