Compared to CD8+CXCR5- T cells, CD8+CXCR5+ T cells produce different levels of interferon (IFN)-γ and tumor necrosis factor (TNF)-α during infection with lymphocytic choriomeningitis virus (LCMV) [8] or HIV [11], and in chronic infections [12]. The gene discussed is CXCR5; the disease is infection.