Infectious agents in reactive arthritis.

It is now clear that the deposition and persistence of bacterial antigens in the joint are significant features of reactive arthritis. It is possible that in some instances this represents persistence of live bacteria, and several studies point to the potential value of antimicrobial therapy. Searches for bacterial DNA and RNA have yielded conflicting data, however, so further developments in this area will be of great importance. It is likely that bacterial antigens interact in some way with class I major histocompatibility complex (MHC) antigens in the pathogenesis of reactive arthritis. However, with the increasing understanding of the structure and function of HLA molecules, some evidence of a classic antigen-class I MHC-CD8 T-lymphocyte interaction is now emerging. Thus far, the mechanisms that link HLA-B27 and bacterial antigens with reactive arthritis remain unclear.