Inherent and iatrogenic immune defects in hairy cell leukemia: revisited.

IMPORTANCE OF THE FIELD: T- and NK-cell abnormalities, decreased number and function of monocytes, neutrophils and dendritic cells, decreased production of certain cytokines and increased incidence of certain autoimmune conditions have been identified in untreated hairy cell leukemia (HCL) patients. These alterations are responsible for an increased rate of infections and additional malignancies in HCL. AREAS COVERED IN THIS REVIEW: The authors offer a focused review of the most relevant preclinical and clinical studies exploring the immune abnormalities in both untreated and treated HCL. WHAT THE READER WILL GAIN: The use of potent immunosuppressive agents such as cladribine and pentostatin in HCL therapeutics has generated increasing concerns about the likelihood of additional immune impairments in these patients. While the NK cells, monocytes and neutrophils were shown to recover shortly after complete responses are achieved with these agents, the CD4(+) T-cell counts may require in excess of 2 - 3 years in order to re-enter the normal range. TAKE HOME MESSAGE: Given the advent of new molecular, genetic and immunologic techniques, a comprehensive characterization of the immune abnormalities in untreated and treated HCL represents a reachable goal and could translate into improved outcomes in clinical practice.