KLRG1 and infection: In contrast, anti-IL-12p40 treatment from day 7 of infection (beginning immediately prior to increase in IL-12 production in WSX-1−/− mice) significantly reduced the frequencies and numbers of effector CD4+ T-bet+ T cells (to WT levels) and repressed the development of KLRG-1+ terminally differentiated cells (Figure 5A–F).