to investigate, whether one of the two alternative therapy strategies (antibiotic plus immunostimulation versus antibiotic plus immunosuppression) in chronic reactive arthritis is therapeutical superior to conventionel standardtherapy (DMARD).|to investigate, whether one or more of the different therapy strategies cause an altered detection of bacterial DNA in the joint or colon.|to measure the antigen-specific and -unspecific immune response (predominantly t-cell response) during therapy and correlate it with the clinical course.|to gain knowledge from these analyses and the clinical course concerning the pathogenesis and the point of attack for possible therapies in chronic reactive arthritis.|to compare cytokine-profiles of CD4- and CD8-positive T-cells from patients treated with infliximab to those treated with etanercept.