VH GENE-EXPRESSION IN HAIRY-CELL LEUKEMIA

Hairy cells are characterized by their typical morphology and expressi on of specific surface antigens, Although their B-cell origin is now c onfirmed, their exact position in B-cell development remains unclear. To better define the origin of hairy cells, we analysed the immunophen otype and the Ig VH nucleotide sequence of seven cases of hairy cell l eukaemia (HCL), Six of them were typical HCL and the remaining case co rresponded to a variant HCL. Analysis of sequenced VH genes revealed t hat the VH1 family was used in one case, VH2 in one, VH3 in two, VH4 i n two and VH5 in one. No preferential usage of VH genes was observed i n this small series. In five cases high rates of somatic mutations wer e observed, with a predominance of mutations and replacements in CDR r egions for three, indicating that these cells originate from cells tha t have been exposed to the hypermutation mechanism. The distribution o f mutations in our small series provides some evidence of a selective mutational process.