Polychromatic flow cytometry and immune cell-specific gene expression profiling ; an integrated approach to identify and validate new biomarkers and signatures of immune responses in chronic inflammatory rheumatic diseases ; Polychromatische Durchflusszytometrie und immunzellspezifische Genexpressionsanalyse ; ein übergreifendes Konzept zur Identifizierung und Validierung neuer Biomarker und Signaturen der Immunreaktion bei chronisch-entzündlichen rheumatischen Erkrankungen

Autoimmune diseases like ankylosing spondylitis (AS), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are characterised by chronic inflammatory immune responses towards the body’s own tissues. Uncertain diagnosis especially in early states and not fully understood etiopathology hamper a curative breakthrough in these diseases. This work introduces a novel multicolour flow cytometry approach for the development of diagnostic procedures based on a complex characterization of the inflammatory condition by simultaneous assessment of numerous peripheral blood leukocyte subsets from the expression of 50 surface CD antigens. A newly developed bioinformatic strategy for the analysis of 800 immunophenotypic parameters revealed a distinct pattern of differentially expressed surface molecules from AS patients compared to healthy individuals. In phenotypes, that determined the pattern of AS from the peripheral blood, the expression of surface molecules CD14, CD1c, CD1a, CXCR4, CD62L and CD69 was most pronounced. An even more enhanced expression of the above-mentioned molecules has also been demonstrated on cells from the synovial fluid of patients with AS, which showed impressively that this pattern typical for a local inflammation could be evaluated already from the analysis of immune cells in the peripheral blood. A comparable analysis of the peripheral blood from AS, RA and SLE patients indicated that not a single marker but a characteristic pattern of differently regulated surface molecules, in terms of an immunophenotypic signature, made it possible to distinguish between various rheumatic diseases. In addition, complex flow cytometric immunophenotyping provides an attractive opportunity to validate candidate genes at the protein level, which were identified by gene expression studies. Cell-specific gene expression analysis of peripheral monocytes from SLE patients showed a dominant type I interferon (IFN) signature. As a reliable surrogate marker for type I IFN-induced responses, the sialic ...