Aim. Investigation of associations of reactive arthritis (ReA) with histocompatibility antigens class I and II and determination of new approaches to assessment of association ReA with antigen HLA B27. Materials and methods. 118 ReA patients,vith associated intestinal and 82 ReA patients with associated urogenital infection were studied The infection was identified bacteriologically, with agglutination reaction, enzyme immunoassay, direct and indirect immunofluorescence, culturing. HLA-antigens were studied in lymphocytotoxic test: locus A. B and C in all the patients, DR in 65 patients. Results. ReA triggers were intracellularly parasite bacteria: facultative parasites in the enterocolitic variant (Yersinia, as a rule), obligate parasite in the urogenital (Chlamidia, as a rule). HLA B27 antigen runs discovered in 77.5% of patients (RR 45.8), HLA DR1 - in 48.4% of patients (RR 3.3). in urogenital variant HLA B27 antigen occurred more frequently than in enterocolitic: 87.8% (RR 95.6) versus 70.3% (RR 31.5); p < 0.01). In HLA-B27-positive patients compared to HLA-B27-negative ones there were higher ESR (p < 0.001), leukocyte count (p < 0.05), concentrations of CRP and alpha-2-globulins (p < 0.001). Conclusion, In HLA-B27-subjects optimal conditions exist for generalization of obligate parasites and favorable for production of facultative ones. The degree of association of ReA with HLA B27 antigens is dependent on adaptive features of microorganisms appearing in the process of evolution - obligaty and facultativeness of their internal parasitivity.
