Evidence for involvement of activated CD8+/HLA-DR+ cells in the pathogenesis of neutropenia in patients with B-cell chronic lymphocytic leukaemia.
B-cell chronic lymphocytic leukaemia (B-CLL) is often associated with peripheral blood cytopenias resulting, in most cases, from bone marrow infiltration, hypersplenism, or circulating autoantibodies. The present study was undertaken to investigate the possible involvement of a cell-mediated suppression of granulopoiesis in these patients. We studied two groups of patients, 8 neutropenic and 26 non-neutropenic, defined by the arbitrarily taken cutoff count of 2000 neutrophils/microliters. We found that neutropenic patients had higher numbers of peripheral blood CD3+, CD8+ and CD57+ cells, and higher numbers of activated CD8+/HLA-DR+ cells than the non-neutropenic ones. A negative correlation between CD8+ cells and circulating neutrophils, and a suggested negative correlation between CD8+/HLA-DR+ cells and circulating neutrophils were noted in the patients studied. Furthermore, we investigated the capacity of immunomagnetically isolated CD8+ cells to inhibit in vitro colony formation by normal granulocyte/macrophage colony-forming units (CFU-GM) and we found that inhibition was more pronounced when CD8+ cells, added in the culture, were derived from neutropenic than from non-neutropenic patients. The degree of colony inhibition correlated with the number of circulating neutrophils and the numbers of CD8+ and CD8+/HLA-DR+ cells in the patients studied. Since tumour necrosis factor-alpha (TNF-alpha) has been reported to be involved in myelosuppression, we also investigated the capacity of isolated CD8+ cells to release this cytokine into the culture supernatant fluids, and we found that comparable amounts of TNF-alpha were produced after stimulation in both neutropenic and non-neutropenic patients. Elevated serum TNF-alpha concentrations were noted only in a number of neutropenic and non-neutropenic patients. All these data taken together provide strong evidence that a T-cell subpopulation of activated CD8+/HLA-DR+ cells may be involved in the pathogenesis of neutropenia, at least in a subset of B-CLL patients, suppressing myelopoiesis by a TNF-alpha-unrelated mechanism. Efforts to isolate this cell subpopulation by flow cytometry for further analysis and a better understanding of its effect on myelopoiesis in patients with B-CLL are in progress in our laboratory.
Katrinakis
G
G
Division of Haematology, University of Crete School of Medicine, University Hospital of Heraklion, Greece.
Kyriakou
D
D
Alexandrakis
M
M
Sakellariou
D
D
Foudoulakis
A
A
Eliopoulos
G D
GD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017951:Antigen Presentation; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D005260:Female; D006684:HLA-DR Antigens / Q000096:biosynthesis*; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology / Q000503:physiopathology*; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D009503:Neutropenia / Q000276:immunology / Q000503:physiopathology*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D006684:HLA-DR Antigens; D014409:Tumor Necrosis Factor-alpha