CLL-like B-lymphocytes are systematically present at very low numbers in peripheral blood of healthy adults

Abstract

[EN] Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in the Western world. The disease is typically diagnosed in adults >40 years old, who show an expansion (>5 × 109 cells per l) of clonal B-cells with a unique CD5+, CD23+, B-cell receptor (BCR)low immunophenotype in peripheral blood (PB) and bone marrow, frequently in association with involvement of other lymphoid tissues, disease symptoms and a heterogeneous clinical outcome. In parallel, monoclonal B-cell lymphocytosis (MBL), typically characterized by an expansion of clonal CLL-like B-cells (<5 × 109 cells per l), has been also frequently reported in otherwise asymptomatic subjects.1, 2 Increasing evidence suggests that this could represent a pre-leukemic condition, as CLL frequently develops in individuals with previous history of MBL, and MBL cases progress to CLL at a rate of 1% per year.