Inducible T cell co-stimulator (ICOS+) CD4 + T cells were shown to expand in the tumor and peripheral blood of anti-CTLA-4 treated patients in several clinical studies covering a range of solid tumor types [38–44], although their frequency in the periphery was not found to be impacted by CTLA-4 blockade in 2 others [28, 29]. The gene discussed is CD4; the disease is neoplasm.