Immune-Mediation and its Relevance to Skin Disease

By Gay Wardle

As therapists who are working with the skin it is imperative that we understand the role of the immune system in supporting our efforts to optimise a well-balanced and healthy skin as part of our treatment objectives.

We know that the skin is the largest organ of the body and that it is a barrier to protect our body from noxious influences from the environment. It is also a sensory organ, a metabolic organ and an immune organ all wrapped up into one

Langerhan cells, which are epidermal dendritic cells, reside immediately under the stratum corneum and represent an enormous part of our immune system, On the other hand keratinocytes, which are epidermal cells produce cytokines and chemokines play a very important role in any immune response.

The dermis, however, is home to many different types of lymphocytes and dendritic cells that have pathogen reaction pattern receptors. These receptors attract inflammatory cells such as neutrophil cells as well as other white blood cells.

TYPES OF ALLERGENS

When working on the skin it is important to understand how allergens effect the skin and their manifestations.

An allergy is defined as an immunologically mediated hypersensitivity reaction that can lead to disease. These reactions can be classified into several pathogenic types of immune reactions where different pathogens have caused responses.

Immediate hypersensitivity: This is where we see diseases such as urticarial lesions which are classified as Type 1 allergens. Urticarial lesions are defined as wheals or hives that appear on the skin’s surface lasting for several hours and in some cases two to three days. The reaction is caused by histamine being released into the skin causing itchiness, edema and vasodilatation. They may appear on any part of the body and are due to an allergic reaction of some kind. If the condition is present for longer periods of time, then it is classified as an acute urticarial lesion. Generally speaking, urticarial lesions are associated with a food allergy. These conditions respond well when treated with antihistamines and in a clinic the use of LED light and MLD are both very beneficial.

Thrombocytopenic purpura: This is a cytotoxic immune reaction. It is a classic Type 2 reaction in the skin, where anti-bodies against substances on the surface of platelets lead to thrombocytopenia and non-inflammatory purpura. It is not a common condition and is mainly caused by drugs. The condition is a bleeding disorder where the immune system destroys platelets, which are necessary for normal blood clotting.

Immune complex reactions: These are classified as type 3 allergens. Leukocytoclasticvasculitis is a condition that is associated with immune complex reactions. Leukocytoclasticvasculitis may present as pustules, bullae, vesicles and urticarial plaques in the skin. Often itching, burning and pain are associated with the condition.

Apart from being localised to the skin the condition may be associated with systemic involvement. Inflammation of small blood vessels and debris of neutrophil cells are symptoms of leukocytoclasticvasculitis. It is very difficult to pinpoint an exact cause, though it seems that allergies to drugs, food or food additives support the theory of the immune system playing the dominant role. Where there are single occurrences of skin lesions that disappear once the offending drugs or foods have been removed, the condition is labeled acute leukocytoclasticvasculitis. MLD, LED and massage would be the best treatment options for these conditions.

Cellular hypersensitivity: Eczema and dermatitis come into this category. The classifications of eczema/dermatitis are varied with allergic and irritant falling under the title of contact dermatitis. Intrinsic atopic eczema and extrinsic atopic eczema are under atopic eczema or atopic dermatitis. Allergic contact dermatitis is the most common occupational disease in many countries.

Intercellular edema in the epidermis is the easiest way to describe an allergic contact dermatitis. It is characterised by an itchy skin condition caused by an allergic reaction to an allergen that has been in contact with the skin. If the allergen that has caused the reaction is not identified the person may have persistent or relapsing dermatitis. Characteristics of allergic contact dermatitis in the acute stages would manifest as pruritic papules and pustules that may develop up to one week or longer post contact with the allergen.

Look for things like nickel, rubber gloves, plants, hair dyes, henna tattoos or temporary tattoos, textiles, preservatives, fragrances, sunscreens, corticosteroids, and many other chemicals which are the likely courses of allergic contact dermatitis.

The reactions begins when molecules that are chemically reactive bind with self-proteins to generate haptenisation. Haptens are able to penetrate through intact skin though where there is an impairment in the barrier function patients have an increased risk of sensitisation. Haptens activate Toll-like receptors and activate innate immunity.

Keratinocytes are crucial for the development of ACD as they express most Toll-like receptors that allow them to respond to haptens. Keratinocytes are also a source of interleukin 10, which is an immune-suppressive cytokine that can limit the extent of contact hypersensitivity. It is believed that the longer a person has severe dermatitis, the longer it will take to resolve the problem.

Atopic eczema: This is the most common inflammatory skin disease in childhood starting as early as 6 to 12 weeks of age, though it also occurs in adult hood years. The condition manifests through extreme itchiness where the skin can be scratched so severely that it bleeds. Often bed clothes are bloody, and the quality of life is highly disturbed.

The barrier function is disturbed which most likely due to a mutation in the filaggrin gene. Filaggrin is a protein forming the cornified envelope that helps enable keratin filaments to attach to lipids in the corneum layer. So, when filaggrin is defective the skin becomes dry and shows epidermal barrier dysfunction. The dysfunction is associated with a higher risk of atopic eczema.

Some causes for atopic eczema could be housedust mites, pollen, animals, and foods. Parents with children suffering from the disease often go to many lengths with elimination of foods from the diets. Sadly, this has caused more issues with malnutrition. There is no miracle cream or pill that can help the condition though basic treatments to help maintain the barrier function have been very helpful.

There is no other organ that shows a similar wide spectrum of different pathophysiologic mechanisms as well as clinical manifestations of allergic reactions like the skin.

Gay Wardle is a well-known multi-awarding winning industry expert and a renowned lecturer who conducts advanced skin analysis training for businesses and their staff on all issues pertaining to skin science. Contact Gay on 0418 708 455 or book on-line www.gaywardle.com.au Email: education@gaywardle.com