Role Of IL-17A In Propionibacterium Acnes-induced Sarcoidosis-like Granulomatosis In Mice

ObjectivesBased on the successful induction of sarcoidosis granulomatous mouse model by propionibacterium acnes in the early stage of our research group,to explore the pathogenic mechanism of IL-17A in sarcoidosis.MethodsWild type C57BL/6 mice were randomized to 3 groups:WT-PA group,WT-PBS group,WT-PA+IL-17Ab group.IL-17A gene knockout(IL-17A-/-)mice were randomized to 2 groups:KO-PA group and KO-PBS group.WT-PA group(n=32)and KO-PA(n=32),in which mice were pre-sensitized by intraperitoneal injection of inactivated PA(0.25 mL,2 mg/mL)and then at 14th,28th,and 42th day after the pre-sensitization the mice were inoculated intratracheally with inactivated PA(0.05 mL,10 mg/mL);WT-PBS group(n=32)and KO-PBS group(n=32),in which mice received intraperitoneal injection of PBS(0.25 mL)and intratracheal inoculation of PBS(0.05 mL)in the same manner as the WT-PA group.WT-PA+IL-17Ab group(n=32),in which wild type mice were pre-sensitized with intraperitoneal injection with inactivated PA(0.25mL,2mg/mL),injected with IL-17Ab(30μg/20g)intraperitoneally at the 14th day after the pre-sensitization,and inoculated intratracheally with inactivated PA(0.05 mL,10 mg/mL)4 hours after the IL-17Ab injection,the 28th,and 42th day after the pre-sensitization.Peripheral blood,BALF,and lung tissue samples of each group were collected on the 17th,21st,28th,and 56th day,respectively.Results1,Lung histopathology:WT-PA group showed inflammatory cell infiltration in t he lung tissues on the 17th,21st,and 28th day,and loose granuloma on the 56th day.The KO-PA and WT-PA+IL-17Ab group showed reduced inflammatory cell infi ltration in the lung tissues on the 17th,21st,and 28th day and no loose granuloma on the 56th day compared with the WT-PA group.2.Detection of inflammatory cells and inflammatory cytokines:Compared with the WT-PA group,the KO-PA group and WT-PA+IL-17Ab group had significantly reduced Th17%(KO-PA vs.WT-PA,P<0.0001;WT-PA+IL-17Ab vs.WT-PA,P<0.0001)in the peripheral blood collected on the 56th day,significantly higher Thl%(KO-PA vs.WT-PA,P=0.0005;WT-PA+IL-17Ab vs.WT-PA,P=0.0262)and Treg cell%(KO-PA vs.WT-PA,P=0.0444;WT-PA+IL-17Ab vs.WT-PA,P=0.0493),and significantly lower Th17/Th1(KO-PA vs.WT-PA,P<0.0001:WT-PA+IL-17Ab vs.WT-PA,P<0.0001)and Th17/Treg ratios(KO-PA vs.WT-PA,P<0.0001;WT-PA+IL-17Ab vs.WT-PA,P<0.0001).Compared with the WT-PA group,the KO-PA group showed significantly lower levels of TH17-associated inflammatory factors in the BALF collected on the 56th day,including IL-17A(p=0.0015)and IL-23(p=0.0015),but higher levels of Treg-associated inflammatory factors including TGF-β1(p=0.0009)and IL-10(p=0.0190).WT-PA+IL-17Ab group showed significantly lower levels of TH17-associated inflammatory factors in the BALF collected on the 56th day,including IL-17A(p=0.0003)and IL-23(p=0.0046),but higher levels of Treg-associated inflammatory factors including TGF-β1(p=0.0226)and IL-10(p=0.0226).ConclusionsIL-17A plays an important role in promoting inflammation in sarcoidosis granuloma tissue formation.