Langerhans cells and skin ageing

The skin is the largest, most visible and outermost layer of the body with an extensive surface area of approximately 18 m2. It is a dynamic, regenerating organ and is the body’s primary defense structure. It is the first line of defense against several external and environmental pathogens.
Langerhans cells
Specialized immune cells are present in skin such as Langerhans cells. They are also found around blood vessels, in the mucosa of the mouth, foreskin, and vaginal epithelium. They can be found in other tissues, such as lymph nodes.

The Langerhans cell is named after its discoverer, Paul Langerhans, a German physician and anatomist. Because of their dendritic cell-like appearance, langerhans cells are mistakenly identified as the cells of the nervous system.

Langerhans cells are mobile, dendritic antigen-presenting cells, present in the epidermis of skin, forming a dense network with which potential invaders must interact.
They are uniquely specialized at “sensing” the environment, by extending dendritic processes through intercellular tight junctions to the outermost layers of the skin and thus they act as the regulators of immune responses.
They induce the first reactions against pathogens which come into contact with the skin.
To fulfill their immunoregulatory role, LC (Langerhans cells) leave the epidermis and migrate to the regional lymph node. Antigen uptake by steady-state LCs, can play a critical role in preventing viral infections.

They play a key role in the pathogenesis of various dermatoses (any disease of the skin).
LCs constitute approximately 3–8% of all the cells in the epidermis of the skin. The number and appearance of LC, change depending on the type of dermatosis and also during the skin ageing processes.

Skin ageing

Skin ageing is a complex process and it depends on external, genetic and hormonal factors.
Aging is a complex process leading to biologic attrition at the cellular level that is manifested in several ways.
Skin aging involves chronological or intrinsically aged skin and photoaged skin changes.
Photoaging is caused by repeated exposure to ultraviolet radiation; whereas, intrinsic skin aging is the naturally occurring biological aging processes in sun-protected areas.
Ultraviolet exposure will speed up chronological skin changes, and with increasing age, the impact of photoaging increases and the effect of the underlying genetic tendencies decreases. All of the functions of the skin change with age.
Foreign chemicals, soaps, and antigens may penetrate and injure the skin more easily.
Antioxidant protection is reduced and ultraviolet light causes more damage. Wound healing and barrier disruption become incomplete and slowed. Thermoregulation, sensation, and vascular reserve are also blunted.
Skin immunity decreases with age due to the increased susceptibility to skin infections and rising incidence of skin neoplasms (an abnormal growth of cells). During the process of skin ageing, changes occur in all skin layers and all cells, including the langerhans cells leading to changes in skin immune composition and reduction in langerhans cells..

The structure and number of LC, depend on the type of skin ageing.
In the case of menopausal and chronological ageing, LC are characterized by long and multi-branched dendritic processes and large cell bodies.
In the case of photoageing, the LC has short and poorly branched dendritic processes and small cell bodies.
During ageing, the capacity of Langerhans cells to migrate declines. This compromises immunity and exposes the skin to infectious diseases and cancer.
Langerhans cells number also decreases during ageing and by age 80, the decrease in number may be as much as 50%.
Aging results in Langerhans (dendritic) cells with fewer dendrite projections infiltrating the skin, and with reduced antigen trapping capacity.

Treatment

• Preventive and active treatment are required for aging skin and they include several strategies.
• Essential fatty acids are important to the proper development of skin. The most important factor for healthy skin is adequate moisture.
• Topical nourishment should be provided to enhance maintenance and repair and to enhance skin miniaturization and conditioning.
• Skin cleansers combined with moisturizers help replace and repair the barrier disrupted by cleaning. Moisturizers such as petrolatum-type products or silicone prevent water loss from the skin.
• To reduce skin disruption, frequency of the use of soaps should be minimized and liquid and foam soaps are to be used rather than bar soaps.
• Using a soft cloth and cooler water are some strategies to reduce skin disruption.
• A cleanser that maintains the acidic pH of the skin (about 5.5) is to be used because pH directly affects the integrity of the skin. Cleanser surfactants can cause immediate after-wash tightness.
• Mild moisturizing cleanser provides cleansing benefits without negatively altering the hydration and viscoelastic properties of skin.
• Modern approaches such as skin therapy are used that include topical and oral vitamins, minerals, fatty acids, cholesterol, alpha-hydroxy acids, glycerol, antioxidants, melatonin, creatine, amino acids, peptides, and hormones.
• Topical and oral vitamins that may be of benefit include vitamins A, C, D, niacinamide, panthenol, and pyridoxine.
• Oral and topical applications of selenium, calcium, and zinc, physiologic lipids like fatty acids and omega-3 fatty acids enhance the development of the skin barrier.
• Implementation of curative, and therapeutic treatments for abnormal ailing skin can help restore function.
• Topical therapy can affect degenerative dermal changes and it is extensively supported scientifically also.

The skin, an essential organ that undergoes many changes as the individual ages. It is metabolically active and regenerative throughout life. So, understanding the aging process of skin helps predict the problems of skin in aged people.