TBX21 and infection: Upon closer analysis of the Tbet+ TH1 cell population, we found a subset of cells that were Tbet+GATA3+ double-positive that ranged from 13% - 33% of the activated CD4+ T-cells, and that represented a significantly higher proportion of the population at 21 days post-infection compared to the Tbet+GATA3- cells (Figure 8B).