The Skin is an Active Part In Host Defense and Immunity

To the naked eye, skin is an elegantly simple fabric of multi-toned hues, remarkable in its soft flexibility and wonderfully responsive to touch. What belies this simplicity is the fact that human skin is rich in complexity, performing many roles in the service of your body. One of the most astounding roles your skin plays is in the immune process.

In fact, the skin is an active, and in many ways unique, immunological microenvironment quite different from the other primary interfaces between the body and the environment (namely the mucosae).

Here, below, Jan D. Bos and Martien L. Kapsenberg identify the components of the skin immune system and describe the inflammatory and immunological responses that they can mount. New findings with regard to the immunophysiology and physiopathology of the human integument are emphasized.

Skin is an immunological organ consisting of epidermal cells, i.e. keratinocytes and Langerhans cells (LCs, antigen-presenting dendritic cells), and both innate and acquired immune systems operate upon exposure of the skin to various external microbes or their elements.
Multifunctional antimicrobial proteins and peptides: natural activators of immune systems

In addition to the physical barrier of the stratum corneum, cutaneous innate immunity also includes the release of various humoral mediators, such as cytokines and chemokines, recruitment and activation of phagocytes, and the production of antimicrobial proteins/peptides (AMPs). AMPs form an innate epithelial chemical shield, which provides a front-line component in innate immunity to inhibit microbial invasion; however, this might be an oversimplification of the diverse functions of these molecules. In fact, apart from exhibiting a broad spectrum of microbicidal properties, it is increasingly evident that AMPs display additional activities that are related to the stimulation and modulation of the cutaneous immune system.

These diverse functions include chemoattraction and activation of immune and/or inflammatory cells, the production and release of cytokines and chemokines, acceleration of angiogenesis, promotion of wound healing, neutralization of harmful microbial products, and bridging of both innate and adaptive immunity. Thus, better understanding of the functions of AMPs in skin and identification of their signaling mechanisms may offer new strategies for the development of potential therapeutics for the treatment of infection- and/or inflammation-related skin diseases.

AMPed up immunity: how antimicrobial peptides have multiple roles in immune defense.

Antimicrobial peptides (AMPs) are widely expressed and rapidly induced at epithelial surfaces to repel assault from diverse infectious agents including bacteria, viruses, fungi and parasites. Much information suggests that AMPs act by mechanisms that extend beyond their capacity to serve as gene-encoded antibiotics. For example, some AMPs alter the properties of the mammalian membrane or interact with its receptors to influence diverse cellular processes including cytokine release, chemotaxis, antigen presentation, angiogenesis and wound healing. These functions complement their antimicrobial action and favor resolution of infection and repair of damaged epithelia. Opposing this, some microbes have evolved mechanisms to inactivate or avoid AMPs and subsequently become pathogens. Thus, AMPs are multifunctional molecules that have a central role in infection and inflammation.
Skin peptides: biological activity and therapeutic opportunities.

The skin provides an effective barrier to the loss of body fluids and environmental assault. In addition to the physical barrier provided by the stratum corneum, the skin also contains a chemical barrier consisting of antimicrobial peptides (AMPs), which control microbial growth on the surface. These AMPs also have multiple roles as mediators of inflammation with effects on epithelial and inflammatory cells, influencing cell proliferation, wound healing, cytokine/chemokine production and chemotaxis. This review describes the range of peptides found in the skin, both constitutive and those induced in response to injury. The role these peptides play in normal skin function and in various skin conditions is described. A better understanding of their role in normal and skin disease may offer new strategies in skin disease, dermatology and as cosmeceuticals.

Functions of antimicrobial peptides in host defense and immunity.

Antimicrobial peptides (AMPs) are effector molecules of the innate immune system. AMPs have a broad antimicrobial spectrum and lyse microbial cells by interaction with biomembranes. Besides their direct antimicrobial function, they have multiple roles as mediators of inflammation with impact on epithelial and inflammatory cells influencing diverse processes such as cytokine release, cell proliferation, angiogenesis, wound healing, chemotaxis, immune induction, and protease-antiprotease balance. Furthermore, AMPs qualify as prototypes of innovative drugs that may be used as antibiotics, anti-lipopolysaccharide drugs, or modifiers of inflammation.

Multifunctional antimicrobial peptides: therapeutic targets in several human diseases.

Antimicrobial peptides have emerged as promising agents against antibiotic-resistant pathogens. They represent essential components of the innate immunity and permit humans to resist infection by microbes. These gene-encoded peptides are found mainly in phagocytes and epithelial cells, showing a direct activity against a wide range of microorganisms. Their role has now broadened from that of simply endogenous antibiotics to multifunctional mediators, and their antimicrobial activity is probably not the only primary function. Although antimicrobial peptide deficiency, dysregulation, or overproduction is not known to be a direct cause of any single human disease, numerous studies have now provided compelling evidence for their involvement in the complex network of immune responses and inflammatory diseases, thereby influencing diverse processes including cytokine release, chemotaxis, angiogenesis, wound repair, and adaptive immune induction.

Antimicrobial peptides in innate immune responses.

Antimicrobial peptides (AMPs) are ancient effector molecules in the innate immune response of eukaryotes. These peptides are important for the antimicrobial efficacy of phagocytes and for the innate immune response mounted by epithelia of humans and other mammals. AMPs are generated either by de novo synthesis or by proteolytic cleavage from antimicrobially inactive proproteins. Studies of human diseases and animal studies have given important clues to the in vivo role of AMPs. It is now evident that dysregulation of the generation of AMPs in innate immune responses plays a role in certain diseases like Crohn’s disease and atopic dermatitis. AMPs are attractive candidates for development of novel antibiotics due to their in vivo activity profile and some peptides may serve as templates for further drug development.

It’s only fitting that the immune function should be strongly represented in the organ that is most directly responsible for physically separating the self from the non-self. The skin not only provides immune protection for its own tissue, but plays a role – a role that most professional don’t understand very well – in protecting the whole body.

More action is seen at the biological border between you and your external environment than almost any other area of your body. Bacteria, viruses, mold, yeast, fungus and other threats to health can use the skin as a landing zone to gain entry into your interior. Yet, unless wounds, abrasions or disease are present, most of these would – be invaders are repelled by your skin.

Nevertheless, improving the skin’s cellular defense system is the best way for not only a healthier – looking skin, but can possibly benefit in the health of your body a well.

Vitamins can be one way to help bolster the skin’s cellular defense system. Vitamin E an antioxidant free – radical fighter is known to keep all cells, including those wearing the “immune” tag, safe from degradation. Vitamin E is the most important immune stimulant I have ever seen for both internal and external use. Vitamin A and C and the trace minerals selenium have similar immune – boosting effects. In fact, Dr. Karen Burke, at Cornell University, discovered antioxid-ant applied to the skin can help delay skin cancer or even prevent its formation. Similar reports are found in antioxidants for both internal and external findings.

Plants can also help bolster your skin’s immunity. Like all living things, plants contain the chemicals of life: vitamins, trace minerals, enzy-mes, and proteins. These elements can often penetrate the skin’s barrier, perhaps assisting the immune battle of fighting off skin problems such as blemishes, wrinkles, redness or blotchy skin and/or age spots. Some dermatologists are now beginning to suspect that these and others problems in the skin are due to breakdowns in the skin’s immune system. While more research is needed, certain ingredients are already being targeted as part of a new family of immune boosters for the skin.

Products being sold as cosmetics may contain ingredients that enhance the immune system. But cosmetics cannot make health claims without legally being classified as drugs. That is why most cosmetics use words such as: “appear” “softer looking,” “moisturizers,” “aids in,” and so on.