CD19⁺CD5⁺ cells have decreased CXCR4, CD38, and Ki67 expression following ibrutinib treatment. (A) Reduction of CD38 expression (mean fluorescence intensity ratio [MFIR]) in CD19⁺CD5⁺ cells but not CD19⁺CD5^– cells during 4 weeks of treatment in 4 patients treated with ibrutinib. (B) Surface CD38 expression (left panel; *P < .05) and intracellular Ki67 (right panel; **P < .01) is significantly reduced following 1 week of treatment. MFIR of intracellular phospho-ERK (pT202/Y204/ERK1/2) of CD20⁺CD5⁺ cells from healthy participants or MCL patients treated with ibrutinib before treatment (day 1 [D1]) and after 1 week of treatment (D8) (lower panel; *P < .05). (C) Significant reduction of surface CXCR4 expression (MFIR) in CD19⁺CD5⁺ cells following 1 week of ibrutinib treatment (n = 14; *P < .05). The line between the dot plots shows the mean. (D) CXCR4 and CD38 expression from LN biopsies and PBMCs (PB) of three MCL patients (patients A, B, and C) not treated with drug. (E) Plasma chemokine and cytokine concentrations on day 8 (D8; left) or day 29 (D29; right) of ibrutinib-treated MCL patients compared with pretreatment times 100% (n = 9).