Skin-associated lymph tissue consists of Langerhans' cells
Langerhans' cells are a type of resident macrophage found in
the epidermis of skin.
When Langerhans' cells are depleted, the skin can neither
initiate an immune response nor support a skin-localized
delayed hypersensitivity response.
What causes Langerhans' cells to become depleted?
May 6, '07
the spectrum of ultraviolet rays is divided into three regions: uvc (200-290 nm), uvb (290-320 nm) and uva (320-400 nm). uva is subdivided into short wave or uva ii (320-340 nm) and long wave or uva i (340-400 nm). uvc is very toxic and carcinogenic to humans. uvb and uva radiation causes sunburn, photoageing and skin cancers. the epidermis absorbs the uvb but uva penetrates deep into the skin. the amount of solar ultraviolet radiation reaching the earth’s surface depends upon thickness of ozone layer, latitude, altitude and season. the ozone layer is a canopy of oxygen in the atmosphere that blocks all uvc and part of uvb radiation2. gradual depletion of ozone by chlorofluorocarbons (a product of refrigeration and air-conditioning units) is responsible for increasing incidence of photoageing and skin cancers. the intensity of ultraviolet radiation on the earth’s surface is high around the solar zenith, at high altitudes near the equator and in summer. radiation intensity of ultraviolet rays is increased by reflection from snow (85%), sand (25%) and rippling water (5%). it is decreased by clouds (20 - 90%) and by traveling through water (60% for every 50 cm). an individual’s susceptibility to photoageing and skin cancers also depends upon melanin content of the skin. fair-skinned people are more prone to benign and malignant skin changes than asians and blacks. cigarette smokers and outdoor workers (sailors and farmers) are severely affected3. photoaged skin shows many histological changes. in epidermis there is increased compaction of stratum corneum, increased thickness of granular cell layer, irregular cellular hyper or hypoplasia, nuclear atypia, reduced or increased number of dopa-positive melanocytes, reduced population of langerhan’s cells, elongation of rete ridges and reduced mucin content. dermis shows decreased collagen, increased glyco-seaminoglycanes, increased elastin, fragility of blood vessels and concentric hyperplasia of sebaceous glands4. there is contraction of septae in subcutaneous fat. (from http://www.pjms.com.pk/issues/octdec01/page2.html)
Last edit by IMustBeCrazy on May 6, '07