STAT1 and infection: STAT1+/+ mice displayed a significantly higher titer of IgG2a anti-T. crassiceps antibodies than STAT1−/− at 4 and 8 weeks post-infection (Figure 1B), whereas there were no significant differences in IgG1 production between STAT1+/+ and STAT1−/− mice at any time during infection (Figure 1C).