As mentioned above, a critical AID co-factor might not be expressed in U-CLL cells because of the activation/maturation pathway these cells might follow (T-cell dependent vs. T-cell independent [32]), which would make the AID-expressing subset of lymphocytes unable to generate V region mutations but capable of CSR [45] and therefore continued interaction with an auto- (or exo-) antigen might drive the proliferative subsets of IgG-positive / AID-positive cells that are often observed in U-CLL [26]. Here, AICDA is linked to B-cell chronic lymphocytic leukemia.