Abstract
Monocytes are one of the least studied immune cells with a potentially important role in the pathogenesis of chronic lymphocytic leukemia (CLL). Nevertheless, data regarding the role of subpopulations of monocytes in the CLL microenvironment are still limited. For the very first time, this study presents an assessment of monocyte subsets divided according to SLAN and CD16 expression in CLL patients. The study involved 70 freshly diagnosed CLL patients and 35 healthy donors. Using flow cytometry, monocyte subpopulations were assessed among PBMCs. CD14+ monocytes can be divided into: “classical” (CD14+CD16−SLAN−), “intermediate” (CD14+CD16+SLAN−) and “non-classical” (CD14dimCD16+SLAN+). In our study, we noted an increased percentage of non-classical monocytes with intracellular expression of TNF and IL-12. On the other hand, among the intermediate monocytes, a significantly higher percentage of cells synthesizing anti-inflammatory IL-10 was detected. The percentage of CD14dimCD16+SLAN+ monocytes producing TNF and IL-12 decreased with the stage of CLL and inversely correlated with the expression of the prognostic factors ZAP-70 and CD38. Moreover, the percentage of CD14dimCD16+SLAN+ monocytes producing TNF and IL-12 was lower in CLL patients requiring treatment. This may indicate the beneficial effect of non-classical monocytes on the anti-tumor response.
Highlights
In chronic lymphocytic leukemia (CLL), one may observe several immune abnormalities, among which one can find changes in monocyte count and function
The transmembrane isoform (FcγRIIIa) is located on monocytes, macrophages and NK cells and is involved in the antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism [6,7], while the FcγRIIIb form is present on the surface of neutrophils [8]
The Percentage of the SLAN-Positive and SLAN-Negative CD16+ Monocytes Is Increased in CLL
Summary
In CLL, one may observe several immune abnormalities, among which one can find changes in monocyte count and function. Initial studies have shown that the population of peripheral blood monocytes is heterogeneous due to the different expression of surface markers, namely CD14 and CD16 (FcγRIII) [1,2]. The transmembrane isoform (FcγRIIIa) is located on monocytes, macrophages and NK cells and is involved in the antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism [6,7], while the FcγRIIIb form is present on the surface of neutrophils [8]. We proved that, within CD16-positive monocytes, it is possible to distinguish cells with similar levels of expression of CD14 and CD16 molecules (CD14+CD16+). They were identified as the so-called intermediate monocytes. Numerous attempts were made to understand the phenotypic and functional heterogeneity of each of the three discovered monocyte subpopulations [3,11]
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