Although we observed by flow cytometry an upregulation of PD-1 in both CD4+ and CD8+ T cells (S6A and S6B Fig) and in Pdcd1 gene expression (S1B Fig and S1C File) during the acute phase of infection, its antibody-mediated blockade failed to enhance parasite clearance in AT (S6C and S6D Fig). The gene discussed is PDCD1; the disease is infection.