CXCL12 and B-cell chronic lymphocytic leukemia: In particular, BAFF, APRIL and CXCL12 are linked to concomitant downregulation of Bim and increased pro-survival expression.27, 28, 29 Furthermore, stromal cell interaction, particularly with follicular dendritic cells, has been identified as a major determinant of survival in CLL and the Eμ-Tcl1 Tg model, via CD44-mediated Mcl-1 upregulation and subsequent apoptotic resistance.48, 49 Cumulatively, these studies suggest a conserved link between BCR, cytokines/chemokines and cellular interactions in the regulation of intrinsic apoptosis and B-cell homeostasis.