Signaling through pathogen-associated and damage-associated molecular patterns drives chronic inflammation in diseases like rheumatoid arthritis. Bacterial DNA, peptidoglycans, muramyl dipeptide and viral molecules have been found in arthritic joints. These microbial pathogen-associated molecular patterns (PAMPs) can drive inflammation through the membrane-bound (Toll-like receptor (TLR)) and cytosolic (NOD-like receptor (NLR)) pattern recognition receptors (PRRs). The resulting release in inflammatory cytokines can drive the damage of host tissue releasing damage-associated molecular patterns (DAMPs), such as high-mobility group box protein 1, GP96, heat shock proteins and ATP, which also activate both types of PRR resulting in a vicious cycle of inflammation.
McCormack et al. Arthritis Research & Therapy 2009 11:243 doi:10.1186/ar2729