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β-Defensin-4 is a peptide with antimicrobial properties that protects the skin and mucosal membranes of the respiratory, genitourinary, and gastrointestinal tracts.¹ It induces migration of monocytes in vitro when used at a concentration of 10 nM but does not affect migration of neutrophils and eosinophils.² β-Defensin-4 (30 μg/ml) stimulates gene expression and production of IL-6, IL-10, CXCL10, CCL2, MIP-3α, and RANTES by keratinocytes.³ It also stimulates calcium mobilization, migration, and proliferation of keratinocytes when used at concentrations of 30, 10, and 40 μg/ml, respectively. β-Defensin-4 induces IL-31 production by human peripheral blood-derived mast cells in vitro when used at a concentration of 10 μg/ml and by rat mast cells in vivo following a 500 ng intradermal dose.⁴ It also inhibits growth of E. coli, P. aeruginosa, and S. aureus with lethal concentration (LC) values of 5, 12, and 15 μM, respectively, of S. carnosus (MIC = 4.5 μg/ml), and of C. albicans with a minimum fungicidal concentration (MFC) value of 7.5 μM.^2,5

1. Lehrer, R.I. Primate defensins Nat. Rev. Microbiol. 2(9),727-738(2004).
2. García, J.R., Krause, A., Schulz, S., et al. Human β-defensin 4: A novel inducible peptide with a specific salt-sensitive spectrum of antimicrobial activity FASEB J. 15(10),1819-1821(2001).
3. Niyonsaba, F., Ushio, H., Nakano, N., et al. Antimicrobial peptides human β-defensins stimulate epidermal keratinocyte migration, proliferation and production of proinflammatory cytokines and chemokines J. Invest. Dermatol. 127(3),594-604(2007).
4. Niyonsaba, F., Ushio, H., Hara, M., et al. Antimicrobial peptides human β-defensins and cathelicidin LL-37 induce the secretion of a pruritogenic cytokine IL-31 by human mast cells J. Immunol. 184(7),3526-3534(2010).
5. Sharma, H., and Nagaraj, R. Antimicrobial activity of human β-defensin 4 analogs: Insights into the role of disulfide linkages in modulating activity Peptides 38(2),255-265(2012).