IL4 and B-cell chronic lymphocytic leukemia: Previous studies have found that ibrutinib markedly improves T cell numbers and function in CLL patients.35,45 Furthermore, ibrutinib has been shown to increase the production of pro-inflammatory cytokines IFN-γ, IL-6, and TNF-α and concomitantly suppress the production of anti-inflammatory cytokines IL-4, IL-13, and IL-10.1,46 Consistent with these findings, we also found that the splenocytes of ibrutinib-treated mice showed enhanced proliferation and skewed TH1 responses through elevated levels of IFN-γ, IL-6, and TNF-α.