ZAP-70 expression is associated with increased CD4 central memory T cells in chronic lymphocytic leukemia: cross-sectional study

ABSTRACT Background: Although chronic lymphocytic leukemia is basically a B cell disease, its pathophysiology and evolution are thought to be significantly influenced by T cells, as these are probably the most important interaction partner of neoplastic B cells, participating in their expansion, differentiation and survival. Chronic lymphocytic leukemia B cells may also drive functional and phenotypic changes of non-malignant T cells. There are few data about the association between memory T cells and prognosis, especially related to ZAP-70, a common reliable surrogate of the gold standard chronic lymphocytic leukemia prognostic markers. Objective: The aim of this study was to investigate whether the expression of ZAP-70 in chronic lymphocytic leukemia patients is associated with abnormal patterns of the distribution of naïve and memory T cells related to crosstalk between these cells. Methods: In this cross-sectional, controlled study, patients with chronic lymphocytic leukemia were compared with healthy blood donors regarding the expression of ZAP-70 and the distribution of naïve and memory T cell subsets in peripheral blood as measured by flow cytometry. Results: ZAP-70 positive patients presented an increased frequency and absolute number of central memory CD4+ T cells, but not CD8+ T cells, compared to ZAP-70 negative patients and age-matched apparently healthy donors. Conclusions: Because central memory CD4+ T cells are located in lymph nodes and express CD40L, we consider that malignant ZAP-70-positive B cells may receive beneficial signals from central memory CD4+ T cells as they accumulate, which could contribute to more aggressive disease.

Involvement of memory T-cells in the pathophysiology of chronic lymphocytic leukemia

The role of T-cells in the pathogenesis of chronic lymphocytic leukemia has recently gained much attention due to the importance of the constant interaction between neoplastic B-cells with microenvironment substratum and T-cells. It is believed that these interactions modulate the clinical course of the disease, mainly through the regulation of the expansion, differentiation, and survival of chronic lymphocytic leukemia B-cells. Importantly, this crosstalk may also change the number, function, and memory phenotype of normal T-cells, thereby altering the amplitude and/or efficiency of adaptive immunity in chronic lymphocytic leukemia patients. The present study presents an overview on important aspects of this immunological crosstalk, particularly on the abnormalities of chronic lymphocytic leukemia B-cells and the alterations in normal T-cells, with focus on the CD4 memory T-cell compartment that could offer survival signals to chronic lymphocytic leukemia B-cell clone(s) and contribute to the establishment and progression of the disease. The authors believe that understanding the biological consequences of the interaction between normal T- and neoplastic B-cells in chronic lymphocytic leukemia may allow for improvements in the prognostic information and therapeutic approaches for this disease.