This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
What is the mechanism of acute rheumatic lever - 
Select and explain. 
A. Cross reactivity with host antigen, B. Innocent by slender effect, C. Due to toxin secretion by streptococci, D. Release of pyrogenic cytokines
A: Cross reactivity with host antigen
Answer: A: Cross reactivity with host antigen 
Explanation: Rheumatic fever is an acute, immunologically mediated, multisystem inflammatory disease that occurs after group A b-hemolytic streptococcal infections (usually pharyngitis, but also rarely with infections at other sites such as skin). Rheumatic hea disease is the cardiac manifestation of rheumatic fever. Acute rheumatic fever is a hypersensitivity reaction classically attributed to antibodies directed against group A streptococcal molecules that also are cross-reactive with host antigens. (Robbins basic pathology,9th edition,pg no.391)