Analysis of VH genes rearranged by individual B cells in dermal infiltrates of patients with mycosis fungoides

Abstract

SUMMARY In patients with cutaneous T cell lymphomas such as mycosis fungoides B cells can frequently be detected in the lymphocytic dermal infiltrate. To analyse their immunoglobulin heavy chain gene repertoire, single B cells were obtained from tissue sections of two typical patients with mycosis fungoides using hydraulic micromanipulation followed by specific amplification of the respective gene segments by single-cell polymerase chain reaction (PCR) technique. A total of 21 VHDJH genes was sequenced. From each individual B cell a single productive VHDJH rearrangement was obtained. There was no clonal relationship detected between any of these rearrangements suggesting polyclonality of the infiltrating B cells. The representation of VH families was in accordance with the germ-line complexity. A remarkably high number of VH genes (5/13 in patient 1; 3/8 in patient 2) was completely or nearly germ-line-identical. Five of seven VH4 family genes were nearly unmutated. On the other hand, most of the VH3 gene family members were somatically mutated in an antigen-driven manner. The proportion of germ-line-identical VH genes, the usage of individual VH, D, JH gene elements, and the pattern of somatic mutations found in the B cells infiltrating skin lesions of patients with mycosis fungoides resembles the peripheral blood repertoire, suggesting a bystander role of these cells.