Background Immune thrombocytopenia (ITP) is an autoimmune disorder. Deficiency of immune tolerance in antigen-presenting cells and cross-communication between antigen-presenting cells and T cells are involved in the pathogenesis of ITP. Macrophages can polarize into proinflammatory M1 or anti-inflammatory M2 phenotypes in response to different environmental stimuli, and have diverse immunologic functions. Objectives To investigate the M1/M2 imbalance in ITP and whether high-dose dexamethasone (HD-DXM) or all-trans-retinoic acid (ATRA) could restore this imbalance. Methods The numbers of M1 and M2 macrophages in the spleens of ITP patients and patients with traumatic spleen rupture were analyzed by immunofluorescence. Monocyte-derived macrophages were cultured and induced with cytokines and drugs. The expression of M1 and M2 markers and functions of M1 and M2 macrophages before and after modulation by HD-DXM or ATRA were evaluated with flow cytometry and ELISA. Results There was preferred M1 polarization in ITP spleens as compared with healthy controls. Monocyte-derived macrophages from ITP patients had increased expression of M1 markers and impaired immunosuppressive functions. Either HD-DXM or ATRA corrected this imbalance by decreasing the expression of M1 markers and increasing the expression of M2 markers. Moreover, HD-DXM-modulated or ATRA-modulated macrophages suppressed both CD4 and CD8 T-cell proliferation and expanded CD4 CD49 LAG3 type 1 T-regulatory cells. HD-DXM or ATRA modulated macrophages to shift the T-cell cytokine profile towards Th2. Treating patients with HD-DXM or ATRA revealed that macrophages induced from responders showed a predominant M2-like phenotype and immunosuppressive function. Conclusions Aberrant macrophage polarization is involved in the pathogenesis of ITP. Either HD-DXM or ATRA is able to correct this imbalance.
Primary immune thrombocytopaenia (ITP) is the most common haemorrhagic disease. Although most patients respond initially to mainstream therapies, such as corticosteroids, immunosuppressants or rituximab, a large proportion of patients fail to respond or relapse. These treatments only affect B lymphocytes or short-lived plasma cells, but not already existing long-lived plasma cells (LLPCs) which persistently secrete antibodies. We hypothesized that LLPCs may play a role in the corticosteroid-resistant or relapsed ITP patients, and bortezomib, a proteasome inhibitor, may act on plasma cells and offer a therapeutic effect. Although a significant difference in the proportion of CD19−CD38hiCD138+ total LLPCs was not observed by flow cytometry, a glycoprotein (GP) IIb/IIIa-specific enzyme-linked immunosorbent spot (ELISpot) assay of sorted CD19−CD138+ LLPCs confirmed the existence of anti-platelet antibody-secreting LLPCs in ITP patients in contrast to healthy controls. Moreover, the LLPCs could be eliminated in the presence of bortezomib by ELISpot assay, which was also confirmed by flow cytometry. Accordingly, a modified monoclonal antibody immobilization of platelet antigen assay of sorted CD19−CD138+ LLPCs revealed that the concentration of anti-platelet antibodies decreased remarkably when cultured with 0.25 ng/mL bortezomib for 5 days. The apoptosis assay demonstrated that bortezomib could induce apoptosis of LLPCs in a concentration-dependent manner. The proteasome activity assay showed that bortezomib significantly reduced the proteasome activity in sorted CD19−CD138+ LLPCs. Furthermore, in active ITP murine models, bortezomib eliminated LLPCs in vivo and alleviated thrombocytopaenia. We conclude that LLPCs participate in the pathogenesis of ITP and bortezomib may have potential as a novel therapeutic regimen.
Immune thrombocytopenia (ITP) is an autoimmune disorder, in which megakaryocyte dysfunction caused by an autoimmune reaction can lead to thrombocytopenia, although the underlying mechanisms remain unclear. Here, we performed single-cell transcriptome profiling of bone marrow CD34+ hematopoietic stem and progenitor cells (HSPCs) to determine defects in megakaryopoiesis in ITP. Gene expression, cell-cell interactions, and transcriptional regulatory networks varied in HSPCs of ITP, particularly in immune cell progenitors. Differentially expressed gene (DEG) analysis indicated that there was an impaired megakaryopoiesis of ITP. Flow cytometry confirmed that the number of CD9+ and HES1+ cells from Lin−CD34+CD45RA− HSPCs decreased in ITP. Liquid culture assays demonstrated that CD9+Lin−CD34+CD45RA− HSPCs tended to differentiate into megakaryocytes; however, this tendency was not observed in ITP patients and more erythrocytes were produced. The percentage of megakaryocytes differentiated from CD9+Lin−CD34+CD45RA− HSPCs was 3-fold higher than that of the CD9− counterparts from healthy controls (HCs), whereas, in ITP patients, the percentage decreased to only 1/4th of that in the HCs and was comparable to that from the CD9− HSPCs. Additionally, when co-cultured with pre-B cells from ITP patients, the differentiation of CD9+Lin−CD34+CD45RA− HSPCs toward the megakaryopoietic lineage was impaired. Further analysis revealed that megakaryocytic progenitors (MkP) can be divided into seven subclusters with different gene expression patterns and functions. The ITP-associated DEGs were MkP subtype-specific, with most DEGs concentrated in the subcluster possessing dual functions of immunomodulation and platelet generation. This study comprehensively dissects defective hematopoiesis and provides novel insights regarding the pathogenesis of ITP.
No abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.