Durchflusszytometrische Analyse der Oberflächenmarker auf Neutrophilen Granulozyten bei Rheumatoider Arthritis

Abstract Background and Objective Neutrophil granulocytes represent the most prominent cell type of the innate immune system during acute inflammation. The activity of these cells can be significantly influenced by surface proteins, which can modulate effector functions and differentiation processes as in the form of receptors. In autoimmune diseases, there may be an upregulation or downregulation of the expression of individual proteins. The aim of this study was to identify previously unknown surface proteins that exhibit altered expression as immune markers on neutrophil granulocytes in rheumatoid arthritis (RA). Methods In a preliminary experiment, the expression of 354 surface proteins was analyzed on neutrophil granulocytes from four RA patients and four healthy donors using a flow cytometry-based multiplex system to identify candidate proteins with potential expression differences between the subject groups. In the main experiment, eight proteins were further analyzed using flow cytometry on neutrophil granulocytes from 59 RA patients and 25 control subjects. For the experimental procedure, RA patients were recruited as blood donors from the Medical Clinic 3 – Rheumatology and Immunology at the University Hospital Erlangen. A control group of healthy donors, matched as closely as possible in terms of age and gender, was used for comparison. Results Of the eight selected proteins from the preliminary experiment, a significantly higher expression of TNFR-2 (p = 0.029) was observed on neutrophil granulocytes in RA patients compared to healthy donors, with no difference between patients with active disease and those in remission. ADAM10 was found to be significantly less expressed in active RA (p = 0.0378) compared to remission (defined by the DAS28 score). At higher disease activity, DEC-205 (p = 0.0401) and CD221 (p = 0.0064) showed significantly increased expression, while Siglec-5 (p = 0.0273) was expressed at lower levels. Conclusion In summary, we found some new proteins that are differentially expressed in RA patients. This might help to understand disease mechanisms better and serve as a potential target for pharmacological treatments. Particularly interesting was TNFR-2 which is upregulated on neutrophil granulocytes in the context of RA.