What do alpha defensins do?

The α and β defensins are small cationic antimicrobial peptides which have the capacity to kill bacteria, fungi, and enveloped viruses by disruption of the microbial membrane. In vivo they are probably most important in phagocytic vacuoles and on the surface of skin and mucosal epithelia.

Where are alpha defensins found?

Alpha-defensins, which have been identified in humans, monkeys and several rodent species, are particularly abundant in neutrophils, certain macrophage populations and Paneth cells of the small intestine.

What do defensins target?

Plant defensins have a range of biological activities and target a wide range of plant pests, including fungi, bacteria, and insects. Additionally, their modes of action are more diverse than those observed for thionins. Plant defensin expression is often induced upon infection with plant pathogens.

How do defensins help prevent viral infection?

The effect of defensins on viral infection is specific to the defensin, virus and target cell. Furthermore, defensins can inhibit or enhance viral infection. This effect is achieved through direct interaction with viral envelopes or through interactions with potential target cells.

What do defensins do to bacteria?

Defensins are capable of killing bacteria or inhibiting bacterial growth through a multiplicity of antimicrobial mechanisms such as direct membrane disruption (11, 65, 66) and inhibition of bacterial cell wall synthesis (67–69). Defensins can also reduce bacterial infection by neutralizing secreted toxins (70–73).

What is human defensin?

Human defensins are cationic peptides of approximately 30 amino acids; they are classified into two subfamilies, α-, and β- defensins, based on their disulfide bond linkages (Fig. 1, reviewed in [1,3,9]). Most human defensins within the same family have similar structure, and form dimers or oligomers [3,10,11].

How do Cathelicidins work?

Cathelicidins rapidly destroy the lipoprotein membranes of microbes enveloped in phagosomes after fusion with lysosomes in macrophages. Therefore, LL-37 can inhibit the formation of bacterial biofilms.

What are the 3 antimicrobial proteins?

Blood and interstitial fluids contain three main types of antimicrobial proteins that discourage microbial growth.

• Interferons (IFN’s) Lymphocytes, macrophages and fibroblasts infected with viruses produce proteins called interferons.
• Complement System.

Where are antimicrobial peptides found in humans?

These peptides are tissue-specific as they are only expressed in the Paneth cells of human intestines. The six human α-defensins (Table 1) share the same disulfide bond pattern. If we number the six cysteines in Roman numbers: I, II, III, to VI, the three disulfide bonds in α-defensins are CI–CVI, CII–CIV, and CIII–CV.

What is another name for human alpha defensin?

Human defensins. Initially human alpha defensin peptides were isolated from the neutrophils and are thus called human neutrophil peptides. Human neutrophil peptides are also known as α- defensins .

What is the difference between alpha and beta defensins?

Alpha defensins are produced mainly in neutrophils and Paneth cells, while the beta defensins are widely expressed in epithelial tissues, including those of the respiratory, gastrointestinal and reproductive systems and the skin. α-Defensins are expressed predominantly in cells of myeloid origin or in Paneth cells ( Selsted and Ouellette, 1995 ).

What are the different types of defensins?

On the basis of their size and pattern of disulfide bonding, mammalian defensins are classified into alpha, beta and theta categories. Alpha-defensins, which have been identified in humans, monkeys and several rodent species, are particularly abundant in neutrophils, certain macrophage populations and Paneth cells of the small intestine.

Where is the defensin gene located?

The defensin gene locus maps to chromosome 8 at 8p21-8pter through 8p23 in human and is syntenic in mice ( Patil et al., 2004; Sparkes et al., 1989; Ouellette et al., 1989a ). α-Defensin genes expressed in cells of myeloid origin consist of three exons, and those expressed in Paneth cells consist of only two exons ( Figure 1 ).