During phagocytosis of an encapsulated bacterium, recognition is greatly enhanced when the organism is coated with specific molecules. Which pair constitutes the two most important opsonins?

• A IgG Fc portion and C3b ✓
• B C5a and leukotriene B4
• C Mannose-binding lectin and properdin
• D Fibronectin and serum amyloid A

Explanation

Coating of microbes with IgG and C3b markedly enhances phagocytosis because neutrophils and macrophages express receptors for both: Fc-gamma receptors bind the IgG heavy chain, and complement receptor 3 and 4 bind iC3b and C3b. Binding of these receptors also activates phagocytosis synergistically. C5a and LTB4 are chemoattractants, while properdin stabilizes the alternative pathway convertase and does not coat organisms.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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