Interleukin-10: Role in increasing susceptibility and pathogenesis of rheumatic fever/rheumatic heart disease.

Streptococcus pyogenes (group A streptococcus) causes rheumatic fever (RF) which later progresses towards rheumatic heart disease (RHD) in the susceptible individuals. RF and RHD both contribute towards increasing global burden of disease, especially in developing countries. RHD is one of the most common acquired heart diseases causing permanent damage to heart valves which ultimately leads to heart failure. In RHD, heart valve lesions are formed which are mediated by autoimmune reaction between streptococcal antigens (M protein and group A carbohydrate epitope GlcNAc) and heart tissues. On the other hand, inflammatory response generated by cytokines promotes chronicity of the disease. Varying concentrations of interleukin-10 (IL-10) in patients and controls are reported and are also found to be associated with IL-10 gene polymorphism in RF/RHD patients. Although the effect of IL-10 gene polymorphism on the functionality of IL-10 is unknown, many investigations suggest an important role of IL-10 and its polymorphism in immune regulation and progression of disease in RF/RHD. This review summarizes the studies based on association of interleukin-10 with RHD in different populations to understand the role of IL-10 in susceptibility and pathogenesis of the disease.