ROUTINE DIAGNOSIS OF LARGE GRANULAR LYMPHOCYTIC-LEUKEMIA BY SOUTHERN BLOT AND POLYMERASE CHAIN-REACTION ANALYSIS OF CLONAL T-CELL RECEPTOR GENE REARRANGEMENTS

Aims-To compare the polymerase chain reaction (PCR) assay with standar d Southern blot (SE) hybridisation for the detection of clonal T cell receptor (TCR) gene rearrangements in large granular lymphocyte (LGL) proliferations; to evaluate the reliability and practicality of the me thods for routine diagnostic use; and to determine the sensitivity of the PCR method. Methods-Blood lymphocytes were isolated from 12 patien ts with persistent CD3(+)CD8(+) lymphocytosis with LGL morphology. Clo nal rearrangements of the TCR gene were demonstrated by SE hybridisati on with a TCR beta constant probe, and by PCR amplification of portion s of the TCR beta and TCR gamma genes. Results-Monoclonal TCR beta gen e rearrangements were detected in eight patients (67%) by PCR analysis and five patients (42%) by SE hybridisation. PCR analysis also showed that seven patients (58%) had monoclonal TCR gamma gene rearrangement s. All cases which had TCR beta clonal rearrangements shown by SE hybr idisation were similarly identified by PCR. Sensitivity tests suggeste d that the TCR beta PCR technique was capable of detecting clonality i n as little as 50 pg of DNA. The TCR beta primers could detect one clo nal cell in approximately 200 or more normal cells (< 0.5%), a sensiti vity level that at least doubles that of the SE hybridisation techniqu e. Conclusions-The use of PCR technology proved to be superior to SE h ybridisation for the routine investigation of suspected cases of LGL l eukaemia. Nine patients (75%) in this study were found to have TCR bet a and/or TCR gamma monoclonal gene rearrangements. This approach is id eal for distinguishing between reactive and clonal LGL proliferation i n a routine diagnostic laboratory.