As a proof of concept, we perform a curated in vivo screen in the LCMV Clone 13 infection model and show that deletion of Ptpn2 enhances CD8+ T cell responses to LCMV Clone 13, thereby revealing a negative regulatory role for Ptpn2 in CD8+ T cell-mediated responses to LCMV Clone 13. The gene discussed is CD8A; the disease is infection.