ZAP70 and B-cell chronic lymphocytic leukemia: Such variability is not unprecedented as Messmer et al (submitted manuscript) have demonstrated differences in CXCL12-mediated MEK and ERK activation in different ZAP-70 subgroups of CLL, and Montresor et al demonstrated differences in CXCL12-mediated lymphocyte function-associated antigen-1 (LFA-1) activation in normal B cells compared to CLL B cells and amongst the cells of different CLL patients [38].