Diagrammatic representation of the effects of IL-4 as elucidated by Aguilar-Hernandez et al and others.^5,6,8  Overall BCR signaling in CLL acts to increase proliferation and survival, whereas CXCR4 appears to mediate lymph node retention as well as survival. (1) IL-4 promotes a BCR pathway to ERK but not NF-κB. (2) IL-4 induces CD79A and CD79B and increases surface IgM. (3) IL-4 represses CXCR4.