CLL.(23) Patients with clinical MBL appear to be predominantly IGHV mutated (77–90%)(18, 19) and have an IGHV repertoire that closely resembles that of mutated CLL with IGHV3-07, IGHV3-23, and IGHV4-34 genes utilized in around half of the cases.(18) While some of these genes (i.e. IGHV 3-07, IGHV 3-23 and IGHV 4-34) have been also found to be expressed in familial population-screening MBL,(15) the overall IGHV repertoire of population-screening MBL appears strikingly different.(8, 9) Specifically, the absence of IGHV 1-69 and an under-representation of both IGHV 4-34 and IGHV 3-23 genes was apparent in individuals with population-screening MBL relative to those with CLL or clinical MBL.(8, 9) While a biased usage of the IGHV 4-59/61 gene in population-screening MBL has been suggested,(8) larger datasets are needed to determine whether or not a distinct restriction in IGHV repertoire occurs in patients with population-screening MBL and to define the random origin from the unselected repertoire expressed by the normal B lymphocyte pool.
