The IFN-γ-expressing T effector cells generated following P. chabaudi were predominantly positive for CXCR5, a marker for TFH cells, and acquired the ability to express IL-21 and IFN-γ, later in the course of infection and in the memory phase of the immune response (Carpio et al., 2015). The gene discussed is CXCR5; the disease is infection.