What is the mechanism of acute rheumatic fever ?

Ans. is 'a' i.e., Cross reactivity with endogenous antigeno Various streptococcal components (specially strep. pyogenes) exhibit antigenic cross reaction with different tissues of the human body. The impoant ones are :Streptococcal component Human tissueCapsular hyaluronic acid synol fluidCell wall protein myocardiumGroup A carbohydrate cardiac valvesCytoplasmic membrane antigen vascular intimaPeptidoglycans skin antigenso This antigen cross reactivity is resoponsible for the production of cross reacting antibodies, i.e. antibodies are formed against streptococcal antigens but they damage host tissue antigens because of similarity between streptococcal antigens and human tissue antigens --> antigenic cross reactivity.o Antigenic cross reactivity is responsible for nonsuppurative manifestations, e.g. acute rheumatic carditis.