Antimicrobial Peptides in Host Defense: Functions Beyond Antimicrobial Activity

Abstract

Antimicrobial peptides are well known for their important roles in host defense by enhancing the barrier function and limiting microbial populations of the skin and mucosa. However, many of these peptides are now known to have additional roles assisting innate and adaptive immune functions. To facilitate innate immunity, antimicrobial peptides activate complement, chemoattract cells (e.g., monocytes, macrophages, T cells, neutrophils, immature dendritic cells, and mast cells), enhance phagocytosis, and modulate the production of chemokines and proinfl ammatory cytokines in other cells. At local sites of initiation, antimicrobial peptides can act as opsonins to enhance phagocytosis by monocytes and phagocytes and can activate cells. In the latter, for example, treatment of osteoblasts and osteoblast-like MG63 cells with human beta-defensin (HBD)2 increases their proliferation rates. Treatment of osteoblast-like MG63 cells with HBD2 and HBD3 increases transcript levels of osteogenic markers for differentiation, increases antileukoprotease (ALP) levels, and enhances mineralized nodule formation. To facilitate adaptive immunity, antimicrobial peptides assist the uptake of antigens by monocytes or other antigen-presenting cells and later direct the process toward a Th1 or Th2 adaptive immune response. More commonly though, antimicrobial peptides induce a mixed response characterized by Th1-/Th2-specifi c antibodies and Th1/Th2 cytokines from antigen-exposed splenocytes of immunized animals. Finally, antimicrobial peptides can be detected in the margins around both oral and cutaneous wounds, and there is

Cytotoxicity of HBD3 for dendritic cells, normal human epidermal keratinocytes, hTERT keratinocytes, and primary oral gingival epithelial keratinocytes in cell culture conditions

“…HBD3 has a strong role in innate and adaptive immunity (Brogden et al, 2015). HBD3 enhances the barrier function of skin or mucosa by regulating permeability and membrane tight junctions in keratinocytes (Kiatsurayanon et al, 2014); stimulates the production of several chemokines from epithelial cells including macrophage inhibitory peptide (MIP) 3α, IFN-inducible protein (IP)-10, and IL-18 (Meisch et al, 2013); chemoattracts monocytes, macrophages, T cells, neutrophils, immature dendritic cells (DCs), and mast cells; promotes differentiation of human mesenchymal stem cells and osteoblasts (Kraus et al, 2012); and regulates complement activation (Prohaszka et al, 1997; van den Berg et al, 1998).…”

A Novel Antimicrobial Peptide Scyreprocin From Mud Crab Scylla paramamosain Showing Potent Antifungal and Anti-biofilm Activity

“…Antimicrobial peptides are short peptides with broad-spectrum antimicrobial activities. As an important component of innate immunity, AMPs have been found in almost all life forms and play important roles in defending against pathogen invasions ( Jenssen et al, 2006 ) and assisting both innate and adaptive immune functions by activating complement and chemoattract cells ( Brogden et al, 2016 ). This non-specific mechanism of action is highly effective, allowing AMPs to possess multiple activities against a variety of microorganisms ( Cushnie et al, 2016 ).…”

HBD3 Induces PD-L1 Expression on Head and Neck Squamous Cell Carcinoma Cell Lines

“…HBD3 is a potent host defense peptide [25]. It has 45 amino acid residues and a monoisotopic mass of 5157.7 Da [26].…”