Human defensins and LL‐37 in mucosal immunity

Doss, Mona; White, Mitchell R.; Tecle, Tesfaldet; Hartshorn, Kevan L.

Defensins are widespread in nature and have activity against a broad range of pathogens. Defensins have direct antimicrobial effects and also modulate innate and adaptive immune responses. We consider the role of human defensins and the cathelicidin LL‐37 in defense of respiratory, gastrointestinal, and genitourinary tracts and the oral cavity, skin, and eye. Human β‐defensins (hBDs) and human defensins 5 and 6 (HD5 and −6) are involved most obviously in mucosal responses, as they are produced principally by epithelial cells. Human α‐defensins 1–4 (or HNPs 1–4) are produced principally by neutrophils recruited to the mucosa. Understanding the biology of defensins and LL‐37 is the beginning to clarify the pathophysiology of mucosal inflammatory and infectious diseases (e.g., Crohn's disease, atopic dermatitis, lung or urinary infections). Challenges for these studies are the redundancy of innate defense mechanisms and the presence and interactions of many innate defense proteins in mucosal secretions.