Background/Purpose: Behçet’s disease (BD) is a systemic vasculitis of unknown etiopathogenesis. Increased neutrophil activation has been previously shown in BD patients and it is unclear whether neutrophil activation occurs constitutively or if it is secondary to a yet unknown stimulus or some serum or tissue soluble factor. The hypersensitivity to Streptococcus sanguinis antigens suggests that infectious agents may play a role in BD pathogenesis. Recently, it has been postulated that BD may be a form of auto-inflammatory disease. The present study investigated several aspects of cellular activation in neutrophils and peripheral blood mononuclear cells (PBMC) of patients with active and inactive BD.
Methods: four study groups were analyzed: active BD (aBD; n=17), inactive BD (iBD; n=26); septic patients (SP; n=10); healthy controls (HC; n=10). BD activity was established as Behçet’s Disease Current Activity Form simplified (BDCAFs) score³2. Flow cytometry analysis evaluated phagocytosis (zymosan particles, Stretococcus pneumoniae and Candida albicans) and the oxidative metabolism before and after stimulation with phorbol myristate acetate (PMA). The shedding of CD62L was determined after stimulation of TLR-2, -3, -4, -5, -7. Microbicidal activity against Streptococcus and Candida was determined by means of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and absorbance read by ELISA. The supernatant of PBMC cultures under TLR or microbial stimuli were used for determination of TNFa, IFNg, IL-12p70, IL-23, IL-6 and IL-10 by ELISA. The supernatant of neutrophil cultures under PMA, LPS or microbial stimuli were used for determination of IL-1β and IL-8.
Results: There was no difference in medication use between aBD and iBD. Phagocytosis, microbial killing activity and oxidative burst assays in PMN and monocytes showed no difference among the four groups. The activated monocyte index of shedding assay showed higher activation by TLR3 in iBD (31±28%, p=0.022) and aBD (27±20%, p=0.029) than in SP (3.4±25%). In contrast, the activation by TLR7 was lower in iBD (27±23%, p=0.022) and aBD (32±27%, p=0.029) than in SP (74±39%). BD monocytes did not differ from HC monocytes regarding activation via TLR stimuli. Neutrophils from aBD produced less IL-1β after stimulus with S. pneumoniae (68±61 pg/mL) than HC (273±174 pg/mL, p=0.05) and showed a trend for lower values comparing to iBD (175±93 pg/mL, p=0.076). There was no difference in the production rate of other cytokines.
Conclusion:
These results showed that phagocytes in BD are not constitutively activated. This negative evidence suggests that the marked involvement of neutrophils in BD pathophysiology may be caused by some kind of stimuli produced by other cells at or close to the target tissues. Thence, further studies should address proteomic analyses of the serum and samples from target tissues in BD in an attempt to identify possible metabolic pathways involved in neutrophil activation in BD.
Disclosure:
S. F. Perazzio,
None;
P. V. S. Pereira,
None;
A. W. S. de Souza,
None;
A. Condino-Neto,
None;
L. E. C. Andrade,
Fleury Medicine and Health Laboratories,
5.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/aspects-of-innate-immunity-in-behcets-disease-a-model-of-autoinflammatory-disease/