CD4 and neoplasm: CTLs recognise antigenic peptides on tumour cells and elicit tumouricidal functions.31,32 However, some studies have shown that CTLs fail to produce inflammatory cytokines that promote tumour cell death.33,34 Ibrutinib has been shown to promote both CD8+ and CD4+ T cells by driving TH1-selective pressure in T lymphocytes.1,35 We therefore determined the effect of ibrutinib treatment on proliferation and effector functions of T cells in vivo.