The frequencies of cells expressing CXCR3 increased among effector CD4+Foxp3− T cells as well as CD4+Foxp3+ Tregs as the infection progressed, with ~50% of effector CD4+Foxp3− T cells expressing CXCR3 compared to 33% of CD4+Foxp3+ Tregs on day 8 p.i. The level of CXCR3 expression was up-regulated on CD4+Foxp3+ T cells from infected compared to naïve B6 mice as shown by significantly higher MFIs on days 8 and 11 p.i. (Supplementary Figure 1B). The gene discussed is CXCR3; the disease is infection.