Expression of host defense scavenger receptors in spondylarthropathy

Objective. Reactive arthritis (ReA) is postulated to be caused by a defecti ve host defense against gramnegative bacteria. HLA-B27 could play a role in this process, but does not account for the many HLA-B27 negative patients. The objective of this study was to test the expression of 3 macrophage sca venger receptors (SRs) that are responsible for innate immunity against gra m-negative bacteria: SR class A type I (SR-AI), SR-AII, and the macrophage receptor with collagenous structure (MARCO). We postulate that defects in s uch receptors might also contribute to the host risk factors that increase the predisposition to ReA and perhaps other subtypes of spondylarthropathy (SpA). Methods. Peripheral blood, synovial fluid, and synovial tissue samples were obtained from patients with recent Salmonella infection, ReA, other SpA, a nd rheumatoid arthritis (RA). The expression of SRs receptors was assessed by semiquantitative reverse transcriptase-polymerase chain reaction. Results. Evaluation of the peripheral blood mononuclear cells (PBMC) from 4 patients who were recently infected with Salmonella, showed that PBMC from 2 patients who developed ReA expressed positive levels of MARCO, while PBM C from 2 patients who recovered from infection without sequelae did not. Th e synovial fluid mononuclear cells (SFMC) from some ReA patients expressed MARCO, but the levels were only moderate. The level of MARCO in the SFMC fr om the SpA patient group was low. In marked contrast, MARCO expression was high in almost all samples of RA SFMC. These findings also extended to syno vial tissues. Conclusion. Expression of the host defense gene MARCO was susceptible to mo dulation, not only during infections, but also in the inflammatory arthriti s conditions RA and SpA. MARCO is a variable to be considered as a candidat e factor that might contribute to ReA.