Regarding the histopathology and immunopathogenesis of acute rheumatic fever (ARF) and rheumatic heart disease (RHD), all of the following statements are correct EXCEPT:
A. Anitschkow cells (caterpillar cells) are pathognomonic for rheumatic carditis and represent activated macrophages
B. Molecular mimicry between streptococcal M protein and cardiac myosin is a proposed mechanism of autoimmunity in ARF
C. CD4+ T cells and B cells are the primary immune cells involved in the pathogenesis of RHD
D. Aschoff bodies are found exclusively in the myocardium and never in the endocardium or pericardium
Explanation
Histopathology and Immunopathogenesis of Acute Rheumatic Fever
Aschoff Bodies: Location and Distribution
Key Point
Aschoff bodies are granulomatous lesions found in ALL three layers of the heart — myocardium, endocardium, and pericardium. They are NOT exclusive to the myocardium.
Table
Layer
Involvement
Lesion Type
Myocardium
Yes
Aschoff bodies, inflammation
Endocardium
Yes
Aschoff bodies, verrucous vegetations
Pericardium
Yes
Aschoff bodies, fibrinous pericarditis
Histological Features of Acute Rheumatic Carditis
1.
Aschoff Bodies — central fibrinoid necrosis surrounded by:
Anitschkow cells (activated macrophages with central wavy ribbon of chromatin — "caterpillar cells")
Aschoff giant cells (multinucleated cells derived from Anitschkow cells)
Lymphocytes and plasma cells
2.
Anitschkow Cells — characteristic but NOT pathognomonic (also seen in other granulomatous conditions and chronic inflammation).
3.
Verrucous Vegetations — small sterile vegetations along the lines of valve closure, seen on endocardium.
High-YieldNEET PG
Aschoff bodies are the hallmark of ARF but are NOT pathognomonic — they can be seen in other conditions. However, they are the MOST specific lesion for ARF.
Molecular Mimicry — streptococcal M protein shares epitopes with cardiac myosin, tropomyosin, and other cardiac antigens; cross-reactive antibodies and T cells attack cardiac tissue.
2.
CD4+ T Cell Response — Th1 and Th17 cells drive inflammation; CD4+ T cells are central to the pathogenesis.
3.
B Cell Response — anti-streptococcal antibodies cross-react with cardiac antigens; produces anti-heart antibodies.
4.
Macrophage Infiltration — activated macrophages form Anitschkow cells and Aschoff giant cells.
Clinical Pearl
The latency period (2–3 weeks between streptococcal infection and ARF onset) reflects the time needed for adaptive immune responses and cross-reactive antibody production.
Why Option 2 is Correct
Aschoff bodies are found in the myocardium, endocardium, AND pericardium — NOT exclusively in the myocardium. This statement is FALSE and is the correct answer to the EXCEPT question.
Robbins 10e Ch 12
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