T-CELL RECEPTOR-BETA GENE REARRANGEMENTS IN LEUKEMIC B-CELLS FROM PATIENTS WITH CHRONIC LYMPHOCYTIC-LEUKEMIA - ASSOCIATION WITH CHROMOSOME-6 DELETIONS

Rearrangement of immunoglobulin genes is a characteristic finding in normal B-cells and in leukaemic cells of B-cell origin. In some leukaemic cells simultaneous cross-lineage rearrangement of immunoglobulin- and T-cell receptor (TcR) genes occur. We have analysed TcR beta gene rearrangement in 100 patients with B-cell chronic lymphocytic leukaemia. All samples expressed CD5, CD19 and CD20 and six patients had rearrangements of both immunoglobulin and TcR beta genes. Analysis of gene expression in cells with TcR beta gene rearrangement indicated production of truncated TcR beta transcripts but no expression of the T-cell markers CD3,CD4, CD8, TcR alpha beta or delta on the cell surface. Three of the patients with both Ig and TcR beta rearrangement (50%) were 44 years or younger at diagnosis and cells from three such patients expressed IgG. Three of the six patients had a terminal deletion of the long arm of chromosome 6 with different breakpoints, with or without other chromosomal abnormalities, whereas 6q deletions were found in 4/94 patients without TcR beta gene rearrangement (4.3%) (P=0.001). This study indicates a correlation between TcR beta gene rearrangement and deletion of chromosome 6q.