THE MAJORITY OF HUMAN TONSILLAR CD5+ B-CELLS EXPRESS SOMATICALLY MUTATED V(CHI)4 GENES

We have fractionated human tonsillar B cells on the basis of CD5 expression and determined the nucleotide sequences of immunoglobin light chain variable (V) regions encoded by the single member of the V(kappa)4 gene family in both CD5+ and CD5- populations. The majority of cDNA from both CD5+ and CD5- B cells populations harbored somatic mutations. Thus, human tonsillar CD5+ B cells, unlike their murine counterparts, are capable of activating their somatic hypermutation mechanism, resulting in the accumulation of somatic mutation in the V(L) regions.