The T cell costimulators ICOSLG (inducible T cell costimulator ligand) and PD-L2 were downregulated during infection, as was butyrophilin subfamily 3 member A1 (BTN3A1), recently shown to present phosphoantigens to Vγ9Vδ2+ T cells (Vavassori et al., 2013). The gene discussed is BTN3A1; the disease is infection.