T-large granular lymphocyte lymphoproliferative disorder: expression of CD26 as a marker of clinically aggressive disease and characterization of marrow inhibition

T-large granular lymphocyte lymphoproliferative disorder (T-LGL LPD) is an indolent disease characterized by prolonged cytopenia and the presence of circulating large granular lymphocytes in the patient's peripheral blood. Although the disease is commonly thought of as indolent, most patients eventually require therapy because of recurrent infections secondary to neutropenia as well as a need for frequent blood product transfusions. CD26 is a 110-kDa surface glycoprotein with an essential role in T-cell function, including being a marker of T-cell activation and a mediator of T-cell activating signals. In this study, we evaluated CD26 expression in T-LGL patients and correlate CD26 expression with clinical behaviour. In addition, we examined the potential mechanism of cytopenia that is associated with this disorder. Our findings suggest that CD26 is a marker of aggressive T-LGL LPD and that CD26-related signalling may be aberrant in T-LGL LPD. Furthermore, inhibition of granulocyte-macrophage colony-forming units may be mediated by CD8(+) cells of T-LGL LPD patients and is major histocompatibility complex class I-restricted.