AID protein expression is associated with ongoing SHM in Ramos but not in DLBCL cell lines. (A) Total cell extracts were prepared from 2 Ramos clones that express (cl.6) or lack (cl.1) AID mRNA expression40 and, from each of them, 3 dilutions were analyzed by immunoblotting using anti-AID Abs and β-actin as control (top). In the bottom panel, the AID protein levels from the top panel, quantitated using the NIH Image software and normalized for β-actin (▪), are compared with the levels of ICV in the corresponding rearranged IgV genes (▨), expressed as frequency of mutations and calculated as described in “Materials and methods.” The mutation frequency in the consensus sequence, defined as the sequence identified by direct sequencing and common to all DNA clones analyzed, is indicated in parentheses below the chart (also see Supplemental Table S1). (B) AID protein expression in 10 DLBCL cell lines (top). The correlation between AID protein levels (▪) and the level of IgV genes ICV (▨), assessed as in panel A, is shown in the bottom panel for 6 representative lines. Numbers in parentheses indicate the mutation frequency in the IgV consensus sequence.
