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 n ormal B-cells and in leukaemic cells of B-cell origin. In some leukaem ic cells simultaneous cross-lineage rearrangement of immunoglobulin- a nd T-cell receptor (TcR) genes occur. We have analysed TcR beta gene r earrangement in 100 patients with B-cell chronic lymphocytic leukaemia . All samples expressed CD5, CD19 and CD20 and six patients had rearra ngements of both immunoglobulin and TcR beta genes. Analysis of gene e xpression in cells with TcR beta gene rearrangement indicated producti on of truncated TcR beta transcripts but no expression of the T-cell m arkers CD3,CD4, CD8, TcR alpha beta or delta on the cell surface. Thre e of the patients with both Ig and TcR beta rearrangement (50%) were 4 4 years or younger at diagnosis and cells from three such patients exp ressed IgG. Three of the six patients had a terminal deletion of the l ong arm of chromosome 6 with different breakpoints, with or without ot her chromosomal abnormalities, whereas 6q deletions were found in 4/94 patients without TcR beta gene rearrangement (4.3%) (P=0.001). This s tudy indicates a correlation between TcR beta gene rearrangement and d eletion of chromosome 6q.