In systemic lupus erythematosus (SLE), the defective clearance of apoptotic cellular debris is central to pathogenesis. Which serum protein, when deficient, is most strongly associated with increased susceptibility to SLE due to impaired clearance of apoptotic cells?
- A C1q ✓
- B C3
- C Mannose-binding lectin (MBL)
- D Properdin
Explanation
C1q is the recognition subunit of the classical complement pathway and a key opsonin for apoptotic cell debris. C1q directly binds DNA, phosphatidylserine, and other 'eat-me' signals on apoptotic cells, promoting their phagocytosis by macrophages. C1q deficiency is the single strongest complement-mediated genetic risk factor for SLE (>90% of complete C1q-deficient individuals develop SLE-like disease). Without C1q-mediated clearance, uncleared apoptotic nuclei release autoantigens (DNA, histones, ribonucleoproteins) that stimulate autoreactive B and T cells. MBL deficiency increases infection risk but has only weak SLE association.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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