IDO1 and diffuse large B-cell lymphoma: Working on the hypothesis that macrophages would prove to be prognostically important in HIV-DLBCL, we also measured a number of potential peripheral blood biomarkers of macrophage numbers (including several cytokines, monocyte fluorescence and HLA-DR expression, Treg numbers, IDO activity, immune cell numbers (including monocytes, lymphocytes and neutrophils), ferritin and CRP levels).