A Study On The Level Of Peripheral Blood Neutrophil Activation And Its Significance In Patients With MPO-ANCA Associated Vasculitis

ObjectiveTo detect changes in the expression levels of indicators of peripheral blood neutrophil activation in patients with anti-neutrophil myeloperoxidase antibody(MPO-ANCA)-associated vasculitis(MPO-AAV)and to explore their role in pathogenesis and clinical significance.MethodsThirty-nine patients with MPO-AAV,40 disease controls with Systemic Lupus Erythematosus(SLE)and 32 healthy controls who were clearly diagnosed in our hospital from October 2021 to December 2022 were selected.Peripheral venous blood was collected from all subjects,and the mean fluorescence intensity(MFI)of peripheral blood neutrophils CD11 b,CD35,CD55,and MPO was measured by flow cytometry(FCM).The expression levels of serum MPO,neutrophil extracellular traps(NETs),and endothelialcellspecificmolecule-1(ESM-1)were measured by enzyme-linked immunosorbent assay(ELISA).The differences between MPO-AAV and control groups were compared,and the correlation between each index was analyzed to initially explore the relationship between them and the degree of disease activity,organ damage and clinical data.Results1.General clinical data: a total of 39 patients with MPO-AAV were included,27(69.23%)of them were women and 12(30.77%)were men,aged 35-84(65.38±11.79) years,with a disease duration of 12(4,72)months.Of these,22 cases were in active phase,13(59.09%)in women and 9(40.91%)in men,age 39-84(65.82±12.21)years;the remaining 17 cases were in remission,14(82.35%)in women and 3(17.65%)in men,age 35-78(64.82±11.57)years.patients with MPO-AAV were more Organ damage was more common in the kidneys and lungs,with 33 cases(84.62%)of kidney damage and 27 cases(69.23%)of lung damage.There were 32 healthy volunteers,11 males(34.38%)and 21 females(65.62%),aged 45-77(63.78±6.76).there were no age(t=0.718,P=0.476)and gender(c2=0.104,P=0.747)compositions between the MPO-AAV group and the healthy control group statistically different.2.Neutrophil CD11 b,CD35,CD55 MFI: MPO-AAV patient group were significantly higher than healthy control group(P < 0.01),all higher than SLE group(P < 0.001),and MPO-AAV active phase was significantly higher than remission phase(P < 0.05).Neutrophil intracellular MPO MFI: The MPO-AAV group was lower than the healthy control group(P < 0.05),and the difference with the SLE group was not statistically significant(P > 0.05),and the active phase of MPO-AAV was significantly lower than the remission phase(P < 0.001).3.Serum MPO,NETs,and ESM-1 concentrations were significantly higher in the MPOAAV group than in the healthy control group(P < 0.001)and in the SLE group(P < 0.05).In contrast,serum MPO,NETs,and ESM-1 levels were not statistically different between the two groups in the active and remission phases of MPO-AAV(P > 0.05).4.Neutrophil CD11 b MFI was positively correlated with CD35 MFI and CD55 MFI in the MPO-AAV group(r=0.572,P<0.01;r=0.388,P<0.05);CD35 MFI was positively correlated with CD55 MFI(r=0.669,P<0.01).Serum MPO concentration was positively correlated with NETs and ESM-1(r=0.977,P<0.01;r=0.977,P<0.01);NETs level was positively correlated with ESM-1(r=1,P<0.01).5.CD11 b MFI in the MPO-AAV group was positively correlated with BVAS score(r=0.340,P<0.05);CD35 MFI was positively correlated with ESR and BVAS score(r=0.326,P<0.05;r=0.473,P<0.01);CD55 MFI was negatively correlated with disease duration(r=-0.389,P<0.05),and positively correlated with ESR,CRP,and BVAS scores(r=0.405,P<0.05;r=0.447,P<0.01;r=0.683,P<0.01);intracellular MPO MFI negatively correlated with ESR,MPO-ANCA,and BVAS scores(r=-0.411,P<0.01;r=-0.451,P<0.01;r=-0.525,P<0.01);while serum MPO,NETs,and ESM-1 levels did not correlate with clinical indicators and BVAS(P>0.05).6.CD35 expression was higher in the MPO-AAV with lung damage group [1809.00(1102.00,3363.00)] than in the group without lung damage [1274.50(909.25,1594.25),P=0.031],as was CD55 expression(3424.15±1074.41)than in the group without lung damage(2267.75± 658.14,P=0.001);while the intracellular MPO levels in patients in the group without lung damage(7651.75±3531.80)were higher than those in the group with lung damage(5223.52±2080.12,P=0.043);the intracellular MPO levels in patients without renal damage(9369.67±3366.27)were higher than those in the group with renal damage(5352.67± 2236.86,P=0.001).7.Pulmonary BVAS scores were positively correlated with CD35 and CD55 MFI(r=0.493,P=0.001;r=0.702,P<0.001),and both pulmonary BVAS and renal BVAS scores were negatively correlated with MPO MFI(r=-0.401,P=0.011;r=-0.380,P=0.017).Conclusions1.Peripheral blood neutrophils from MPO-AAV patients are in an activated state with upregulated expression of phenotypes CD11 b,CD35 and CD55,downregulated intracellular MPO levels,degranulation to release MPO,production of Nets possibly leading to endothelial damage and involvement in MPO-AAV pathogenesis.2.CD11 b,CD35,CD55,and MPO MFI were significantly different between the two groups in the active and remission phases of MPO-AAV and correlated with BVAS score,CRP,and ESR,helping to determine the activity of MPO-AAV disease.3.Patients with MPO-AAV with elevated CD35 and CD55 expression may be more prone to lung damage,and those with decreased intracellular MPO expression may be more susceptible to lung and kidney involvement.4.Compared to SLE,which is also an autoimmune disease,neutrophil activation levels were significantly higher in patients with MPO-AAV,suggesting that neutrophils are specific in the pathogenesis of MPO-AAV.