Assessing Clonality and Disease Burden of T-Cell Large Granular Lymphocyte Leukemia (T-LGL) by TCR-V Flow Cytometric Analysis
B Feng, JL Jorgensen, LJ Medeiros, SA Wang. UT MD Anderson Cancer Center, Houston, TX
Background: T-large granular lymphocyte leukemia (T-LGLL) is characterized by a monoclonal proliferation of LGLs of T-cell lineage. Because increased T-LGL are commonly seen in reactive conditions as well as in monoclonal T-LGL proliferations of uncertain significance, the diagnosis of T-LGLL requires assessment of both clonality and tumor burden. In this study we assessed the utility of flow cytometry analysis (FCM) of T-cell receptor b chain gene variable region (TCR-V) repertoires in the diagnosis of T-LGLL.
Design: Peripheral blood samples of 20 T-LGLL patients and 18 controls were analyzed by 4-color FCM assessing CD2, CD3, CD4, CD5, CD8, CD7, CD16, CD26, CD56, CD57, CD158a, 158b, and 158e. Vb expression was studied by using 24 antibodies reactive to 70% of the TCR-V repertoire on the cell population of interest. TCR and TCR gene rearrangement were assessed by PCR in 20/20 T-LGLL and 12/18 controls.
Results: All 20 cases of T-LGLL demonstrated morphologic evidence of bone marrow involvement. By FCM immunophenotyping, 19/20 T-LGLL cases were CD3+CD8+CD57+ and 1 case was CD3+CD4+CD57+.15/20 (75%) T-LGLL cases demonstrated at least an aberrant immunophenotype, with altered CD5 expression most frequent. Abnormal TCR-V expression was detected in 17/20(85%) T-LGLL cases, showing 95% concordance with TCR gene rearrangement results. Strong correlations between absolute counts of the expanded V clone and cells with a T-LGLL immunophenotype cells was observed (r=0.8). Although an abnormal CD4:CD8 ratio was sensitive for detecting T-LGLL, its correlation with the disease burden was poor.
Table 1. Summary of TCR-V Flow Cytometric and Hematologic Parameters from 20 T-LGLL and 18 Control Cases
|ABS Lymphs X10(9)/L||3.53(0.81-23.94)||2.08(0.67-23.12)|
|% of V+ Lymphs||74.00(28-91)||NA|
|ABS V+ X10(9)/L||2.77(0.228-17.65)||NA|
|% of Bone marrow involvement||30.00(8.00-62.00)||NA|
Conclusions: FCM analysis of the TCR-V repertoire is a fast, reliable and quantitative method for assessing T-LGLL clonality and tumor burden. Its clinical utility is not limited to the initial diagnosis but also the disease monitoring during therapy.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 186, Wednesday Morning