CD200 and leukemia: Ibrutinib can reduce the expression of CXC chemokine receptor 4 (CXCR4) in leukemia cells, and inhibit the signal transduction downstream of CXCR4, disrupt the homing of leukemia cells to lymphoid tissue, and promote its release into the circulation, reducing malignant CD200 (OX2) expression on cells and decreasing expression of immunosuppressive cytokines [101].