Detailed Explanation
Defensins are classified into α-defensins and β-defensins based on the spacing of their six conserved cysteine residues. Human α-defensins (HNP-1 through HNP-4, HD-5, HD-6) are found in neutrophil granules (HNP) and intestinal Paneth cells (HD). β-Defensins (hBD-1 through hBD-4) are expressed in skin, airways, and urogenital epithelia. Defensins kill bacteria by disrupting their negatively charged membranes — bacterial membranes are rich in phosphatidylglycerol and lipopolysaccharide, while mammalian membranes are rich in neutral cholesterol and phosphatidylcholine, providing selectivity. Beyond direct antimicrobial activity, defensins recruit immune cells, activate complement, and bridge innate and adaptive immunity.
Key Facts
- Defensins are classified into α-defensins and β-defensins based on the spacing of their six conserved cysteine residues
- Human α-defensins (HNP-1 through HNP-4, HD-5, HD-6) are found in neutrophil granules (HNP) and intestinal Paneth cells (HD)
- β-Defensins (hBD-1 through hBD-4) are expressed in skin, airways, and urogenital epithelia
- Defensins kill bacteria by disrupting their negatively charged membranes — bacterial membranes are rich in phosphatidylglycerol and lipopolysaccharide, while mammalian membranes are rich in neutral cholesterol and phosphatidylcholine, providing selectivity
- Beyond direct antimicrobial activity, defensins recruit immune cells, activate complement, and bridge innate and adaptive immunity
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