<prompt> The mechanism of the development of Acute Rheumatic Fever is which of the following?Cross reactivity with exogenous antigenInnocent bystander effectDue to toxin secretion by streptococciRelease of pyrogenic cytokines  <response>: Acute rheumatic fever results from immune response to group A streptococci Strep. pyogenes which cross-reacts with host tissues. The antibodies directed against the M proteins of streptococci cross react with the self antigens in the hea. In addition, CD4 T cells specific for streptococcal peptides also react with self proteins in the hea and produce macrophage activating cytokines. So, the damage to the hea tissue is a combination of antibody and T-cell mediated reactions 