The Group A carbohydrate antigen of Streptococcus pyogenes exhibits cross-reactivity with human_________________?
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Answer: C. Cardiac valves
Explanation
The Group A carbohydrate antigen of Streptococcus pyogenes shows molecular cross-reactivity with human cardiac valve tissue. This structural mimicry tricks the immune system into attacking host heart valves following a throat infection. Such autoimmune cross-reactivity provides the underlying immunopathological mechanism responsible for rheumatic heart disease. Streptococcus pyogenes is a beta-hemolytic bacterium responsible for pharyngitis, scarlet fever, and skin infections. Molecular mimicry occurs when microbial antigens share similar epitopes with normal host structural proteins. Antibodies and T cells generated against bacterial components inadvertently target healthy human tissues by mistake.
Prompt antibiotic treatment of streptococcal pharyngitis prevents the development of acute rheumatic fever complications. Patients with a history of rheumatic heart disease often require prophylactic antibiotics before undergoing dental procedures. Cardiologists monitor valve function in affected individuals to detect chronic inflammatory damage early. Synovial fluid can be involved in reactive arthralgia, but cardiac valves are the primary site for rheumatic damage. Myocardium is affected in rheumatic carditis, but specific carbohydrate cross-reactivity centers on heart valve structures. Vascular intima is involved in general vasculitis, whereas specific valvular cross-reactivity drives rheumatic heart disease.
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