Background M. Behçet as systemic vasculitis with a genetic susceptibility in association to HLA-B*51 has been claimed to show hyper-reactivity of granulocytes as one important factor in the pathogenesis of the disease. IL-17A primarily found in a T-helper cell subset has been also reported to be expressed in γδ-T-Cells, NK cells and certain myeloid cells. It is implicated as key pro-inflammatory cytokine in different autoimmune diseases.
Objectives In this study, IL-17 expression was investigated in peripheral granulocytes from 15 patients with M. Behçet in comparison to 15 normal controls to investigate influence on hyperreactivity.
Methods Granulocytes were isolated by densitiy gradient centrifugation (Polymorphprep) from citrated blood samples. In addition isolated granulocytes of 9 patients and 7 controls were stimulated with a formyl-peptide (fMLP) for one hour. Expression of IL-17 was investigated by flow cytometry and Western Blotting of cell lysates with a specific monoclonal anti-IL-17 antibody. Enriched granulocytes were tested for purity by the expression of CD66b.
Results Patients tended to have higher levels of CD66b+ granulocytes than controls. In both patients and controls IL-17 expression was found by FACS analysis in CD66b+ CD14- granulocytes irrespective of additional presence of CD11b. These results were confirmed by Western Blotting of lysates of the enriched granulocytes in comparison to the lymphocyte fraction with the specific IL-17 antibody. Stimulation of granulocytes with the bacterial fMLP peptide slightly increased IL-17 expression in controls, but strongly reduced it in the patient
Conclusions Patients with M. Behçet, but also healthy controls express IL-17 in CD66b+ granulocytes which may contribute to pro-inflammatory activities when they migrate into tissues. Negative regulation of IL-17 in response to bacterial formyl-peptides, however, could point to specific defects in granulocytes in immune responses.
Disclosure of Interest None Declared