Molecular immunoglobulin/T-cell receptor clonality diagnosis by gene scan in lymphoproliferative disorders

Abstract

There remains significant controversy over the techniques used for clonal diagnosis of lymphoproliferative disorders because of questions regarding the sensitivity, specificity and throughput. This has stimulated us to explore the use of gene scan to determine clonality of Immunoglobulin (Ig)/T-cell receptor (TCR) (γ gene rearrangement in a variety of morphologically, cytochemically, pathologically and immunophenotypically defined precursor B/T-ALL (12 patients), 5 patients with NHL, 10 patients with CLL and a group of reactive lymphocytosis as a reference group (10 subjects).

Polymerase chain reaction (PCR) was done for IgH gene (FR3a, FR2b, LJH and JH primers) and for TCR γ gene and the malignant clone was identified using gene scan (GS) analysis.

In the ALL group, monoclonality was detected using GS and using IgH (FR2b) 75% had a clonal band, 63% with IgH (FR3a) and 88% with a combination of FR3a/FR2b. The results of TCR γ monoclonality were 50% using primer mix I, 25% using primer mix II and 75% using a combination. In the CLL group, clonal IgH gene rearrangement was detected by FR2b in 80% of cases, while by FR3a clonal rearrangement was detected in 60%, the combination of FR2b and FR3a increased the detection rate to 90%. In B-cell NHL, the FR2b was clonally rearranged in 50% while FR3 was positive in 25%. In reactive lymphocytosis, all cases revealed polyclonal rearrangement with TCR γ primers. The sensitivity and positive predictive value of GS was 100% and the specificity and negative predictive value was 86.6%

In conclusion, gene scanning provides a sensitive and specific method for detection of the malignant clone in PCR product in patients with lymphoproliferative disorders.

Keywords:

• POLYMERASE CHAIN REACTION
• GENE SCAN
• IGH GENE
• TCR GAMMA PRIMER