Abstract
BackgroundAlthough impaired myeloid-derived suppressor cells (MDSCs) recently have been studied in immune thrombocytopenia (ITP), another myeloid-derived cell population signified as M2 macrophages has not been investigated properly in ITP patients. In the present study, we intended to determine the features of circulating M2-like macrophages, to examine its relationship with MDSCs, and to explore their prognostic values in ITP.MethodsPeripheral blood mononuclear cells from healthy controls and primary ITP patients were isolated to test the circulating M2-like macrophages and MDSCs. The circulating M2-like macrophage population defined as CD68+CD163+ and circulating MDSC population as CD11b+CD33+HLA-DR− were determined by flow cytometry. Plasma inflammatory cytokines were measured by multiplex ELISA.ResultsThe percentages of MDSCs were found to be expanded in newly diagnosed patients of ITP, especially among those of the complete response (CR) group (p < 0.0001). Positive linear correlation was verified between percentages of M2-like macrophages and MDSCs. The same correlation was also determined in the CR group. After treatment, the percentages of M2-like macrophages and MDSCs were both increased significantly in CR group, while those patients among the PR + NR group manifested a significant numeric decrease of MDSCs but only a moderate decrease in M2-like macrophages. MIP-1α/CCL3 was negatively correlated with M2-like macrophages while MCP-1 possessed a positive correlation with M2-like macrophages, eotaxin-1/CCL11 was negatively correlated with MDSCs and interleukin-1β (IL-1β) was found to be negatively correlated with both M2-like macrophages and MDSCs.ConclusionsThe present findings indicated critical roles of both circulating M2-like macrophages and MDSCs in ITP. The positive correlation between them might be related to inflammatory factors-mediated bidirectional interactions or partially due to their similar background patterns during differentiation. MIP-1α/CCL3, MCP-1, eotaxin-1/CCL11 and IL-1β might play a critical role in the expansion of both M2 macrophages and MDSCs population in ITP patients, which deserves further investigation.
Highlights
Impaired myeloid-derived suppressor cells (MDSCs) recently have been studied in immune thrombocytopenia (ITP), another myeloid-derived cell population signified as M2 macrophages has not been investigated properly in ITP patients
The present study focused on the correlative observation of M2-like macrophages and MDSCs in ITP
The percentages of circulating MDSCs expand in newly diagnosed ITP patients, it might just reflect the quick response to the pathologic environment without any immunosuppressive properties
Summary
Impaired myeloid-derived suppressor cells (MDSCs) recently have been studied in immune thrombocytopenia (ITP), another myeloid-derived cell population signified as M2 macrophages has not been investigated properly in ITP patients. Impaired MDSCs have been implicated in the pathogenesis of ITP [6] via direct inhibition of T cell activation or the indirect induction of regulatory T cells (Tregs), which could act as a prognostic marker for treatment responses in ITP [7]. As another important myeloidderived cell compartment, macrophages have been implicated to be active in the perturbation of immune tolerance in ITP. M2 macrophages have not yet been investigated properly in ITP patients
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