Peripheral Blood Immune Cell Spectrum Analysis Of Langerhans Cell Histiocytosis,Erdheim-Chester Disease,and Rosai-Dorfman Disease

Background and ObjectivesHistiocytosis,including Langerhans cell histiocytosis(LCH),Erdheim-Chester disease(ECD),and Rosai-Dorfman disease(RDD),are rare diseases characterized by abnormal accumulation of cells originated from the mononuclear phagocyte system.Histiocytes in LCH,ECD,and RDD carry activation mutations in the MAPK pathway,which is regarded as the pivot in the pathogenesis of histiocytosis.However,the pathology and clinical manifestations are distinctive among LCH,ECD,and RDD,there are still substantial gaps from the similar genotype to distinguishing phenotypes.Simultaneously,those pathological histiocytes retained abnormal antigen-presenting cell function,which would recruit suppressive immune cells,promote the suppressive microenvironment in the lesions.In addition,elevated levels of pro-inflammatory cytokines were detected in peripheral blood,which might be secreted by peripheral blood immune cells,aggravating the diseases.Hence,there are two major research fields about the pathogenesis of histiocytosis.Firstly,revealing the progenitor cells of pathogenic histiocytes is the basis of investigating the role of MAPK pathway activation in the proliferation and differentiation in abnormal histiocytes.Secondly,analyzing the inflammatory components comprehensively is vital for understanding the inflammatory state of histiocytosis patients,which will facilitate finding novel treatment targets.This research will analyze the components and phenotypes of peripheral blood immune cells from LCH,ECD,and RDD patients,in order to divulge the circulating progenitor cells of histiocyte and compare the immune cell components among the diseases.Methods and MaterialsPeripheral blood was collected from 9 LCH patient,3 ECD patients,and 3 RDD patients,who were diagnosed between October 2020 and March 2021 in Peking Union Medical College Hospital.Mass cytometry analysis including 42 surface markers was performed,the output data was analyzed by an unsupervised clustering algorithm,and clusters of cells were generated.The phenotypes of cell clusters were translated by a surface marker enrichment model.ResultsIn this study,41 cell clusters,including monocytes,dendritic cells,NK cells,NKT cells,γδT cells,CD8+T cells,CD4+T cells,B cells,and progenitor cells,comprise the intact peripheral immune cell spectrum.Classic monocytes with CD14+CD16-CD163+CD56+phenotype could nearly only be detected in peripheral blood from ECD patients(ECD-01:3.56%;ECD-02:12.16%).In LCH-SS patients,the CD16+NK cells/all NK cells ratio was significantly decreased compared with health controls(LCH-SS vs.health controls,2.48%(2.01-5.88)vs.90.7%(88.7-91.3),p<0.0001).In LCH-MS patients,the CD16+NK cells/all NK cells ratio was also decreased,whereas not statistically significant(LCH-MS vs.health controls,43.8%(0.376-94.3)vs.90.7%(88.7-91.3),p=0.12).The CD56+Tregs were mainly detected in the peripheral blood of LCH patients(CD56+Treg cells/all Treg cells ratio,in health controls,RDD,LCH-SS,LCH-MS,and ECD were 1.06%(0.00-2.39),0.285%(0.201-0.307),0.524%(0.353-3.94),3.68%(1.23-34.1),and 0.235%(0.00-0.469),respectively).In ECD patients,the classic monocytes/all monocytes ratio was significantly increased compared with health controls(ECD vs.health controls,0.955(0.926-0.965)vs.0.854(0.839-0.869),p=0.0035).The Th2 cell/Th1 cell ratio was increased compared with health controls in ECD patients(ECD vs.health controls,0.751(0.547-0.850)vs.0.470(0.331-0.513),p=0.069),whereas no evident differences in RDD,LCH-SS or LCH-MS(in RDD,LCH-SS and LCH-MS were 0.477(0.369-0.779),0.441(0.310-0.643),and 0.562(0.466-0.730),respectively).In RDD patients,the number of γδT cells was significantly decreased compared with health controls(RDD vs.health controls,1.78%(1.49-1.79)vs.5.42%(3.79-5.49),p=0.049).The memory B cells were significantly increased(RDD vs.health controls,0.336%(0.0636-0.406)vs.0.00%(0.00-0.0477),p=0.046).Conclusion1.The classic monocytes with CD14+CD16-CD163+CD56+phenotype in peripheral blood are supposed to be the progenitor cell of ECD histiocytes;2.The components and phenotypes of immune cells from histiocytosis patients exhibit a chronic antigen stimulation and inflammatory state.RDD and ECD shared more immune cell component characteristics.RDD,ECD,and LCH also have distinctive immune cell spectrum features:In LCH patients,the CD16+NK cell/all NK cells ratio was significantly decreased.The CD56+Treg cells could nearly only be detected in LCH patients.In RDD patients,the number of γδT cells was significantly decreased,the number of memory B cells was significantly increased.In ECD patients,the classic monocytes/all monocytes ratio was significantly increased,and the Th2 cells/Th1 cells ratio was increased.