Risk stratification of adult T-cell leukemia/lymphoma using immunophenotyping.

Adult T-cell leukemia/lymphoma (ATL), a human T-lymphotropic virus type 1 (HTLV-1)-associated disease, has a highly variable clinical course and four subtypes with therapeutic and prognostic implications. However, there are overlapping features between ATL subtypes and between ATL and nonmalignant (non-ATL) HTLV-1 infection complicating diagnosis and prognostication. To further refine the diagnosis and prognosis of ATL, we characterized the immunophenotype of HTLV-1-infected cells in ATL and non-ATL. A retrospective study of peripheral blood samples from 10 HTLV-1-uninfected subjects (UI), 54 HTLV-1-infected patients with non-ATL, and 22 with ATL was performed using flow cytometry. All patients with ATL had CD4  CCR4  CD26 immunophenotype and the frequency of CD4  CCR4  CD26 T cells correlated highly significantly with the proviral load in non-ATL suggesting CD4  CCR4  CD26 as a marker of HTLV-1-infected cells. Further immunophenotyping of CD4  CCR4   CD26 cells revealed that 95% patients with ATL had a CD7 (≤30% CD7 cells), whereas 95% HTLV+ non-ATL had CD7 (>30% CD7 cells) immunophenotype. All patients with aggressive ATL had a CCR7 (≥30%), whereas 92% with indolent ATL and 100% non-ATL had a CCR7 (<30%) immunophenotype. Patients with nonprogressing indolent ATL were CD127 but those with progressive lymphocytosis requiring systemic therapy had a CD127 (≤30%) immunophenotype. In summary, HTLV-1-infected cells have a CD4  CCR4  CD26 immunophenotype. Within this population, CD7 phenotype suggests a diagnosis of ATL, CCR7 phenotype identifies aggressive ATL, while CCR7 CD127 phenotype identifies progressive indolent ATL.