PTPRC and B-cell chronic lymphocytic leukemia: In support of this notion, at 3 d after immunization, we found similar frequencies of HEL-specific B220+CD38+GL7+CCR6+ B cells in CLL- and PBS-L–treated animals (Fig. 4 A and B), a population that has been shown to represent a transitional stage between naïve and GC B cells (pre-GCs) (34, 39).