KLRG-1 expressing Th1 cells in infected WSX-1−/− mice appeared highly proliferative but were not more potent sources of IFN-γ or TNF than the KLRG-1− Th1 cells on any examined day following PMA/ionomycin stimulation (Figure S5), and produced only slightly more IFN-γ on day 14 of infection following malaria-antigen stimulation (results not shown), suggesting that they may be atypical terminally differentiated cells. This evidence concerns the gene KLRG1 and infection.