What is the mechanism of acute rheumatic fever -

Ans. is 'a' i.e., Cross reactivity with endogenous antigen Acute Rheumatic fever results from immune response to group A streptococci.The main factor responsible for virulence in infection with streptococcal A group is "M" protein.The body mounts an immune response against streptococci A organism by producing antibodies directed against the "M" protein.Antibodies directed against the "M" protein of streptococci have been shown to cross react with self antigens in the heartThe streptococcal M protein and the human myocardium appears to be identical antigenically.Epitopes present in the cell wall membrane and the A, B, C repeat regions of the "M" protein are immunologically similar to molecules in human myosin, tropomyosin, keratin actin, laminin, vimentin."This molecular mimicry is the basis for autoimmune response that leads to Acute Rheumatic fever".