Langerhans Cell Definition
Langerhans cells are immune cells mostly found in the epidermis that play a critical role in the activation and inhibition of adaptive immunological responses. These are antigen-presenting cells that are a subset of dendritic cells. If a Langerhans cell gets into touch with a pathogen, it eats it whole and fragments it into tiny pieces of protein. To elicit an immunological response, many of these fragments are displayed on the cell surface and transported to lymph node-derived naïve T cells.
What is a Langerhans Cell?
Langerhans cells are immune cells found in the skin (AKA the epidermis). As with other immune cells, Langerhans cells are created in the bone marrow. They circulate in the blood after their release from the bone marrow and migrate to the epidermis, where the immune cells defend it against pathogen invasion.
Langerhans cells are antigen-presenting cells (APCs) in the skin and belong to the dendritic cell family. They capture pathogens as they pass through the epidermis and display their antigens on their surface, activating other immune cells.
Where Are Langerhans Cells Found?
Langerhans cells may be found throughout the epidermis, as well as in the respiratory, digestive, and urogenital tracts. When Langerhans cells come into contact with a pathogen, they then migrate to lymph nodes, where they expose their antigens to naïve T cells, initiating the adaptive immune response.
Function of Langerhans Cells
Dendritic cells, including Langerhans cells, are a kind of dendritic cell. Their major role is to alert other components of the adaptive immune system to the existence of infections, as well as other infectious substances on the epidermis.
Langerhans Cells as Antigen-Presenting Cells (APCs)
Langerhans cells are phagocytic, taking up other cells or particles. Additionally, they are antigen-presenting cells (APCs) that may express pathogen fragments on their cell surface in order to elicit an adaptive immune response.
When a Langerhans cell comes into contact with a pathogen that is detrimental to the skin, it consumes it and degrades it into protein fragments. As part of the Major Histocompatibility Complex, several of these pieces are shown on the top of Langerhans cells (MHC).
Langerhans cells then move to lymph nodes, where they deliver their antigens to naive T lymphocytes. This induces T cells to seek out and eliminate the invading virus, triggering an immune response.
Immune Suppression by Langerhans Cells
Langerhans cells stimulate the adaptive immune response to infections, but they have also been shown to decrease immunological activity. Although “foreign” to the body, the skin is naturally colonised by friendly bacteria that are not known to cause illness. The Langerhans cells coordinate immunological tolerance in the presence of non-pathogenic microorganisms, preventing the immune system from reacting. This prevents the immune system from being activated unnecessarily and maybe harmfully.
Langerhans Cells Prevent Autoimmunity
By establishing immunological tolerance, Langerhans cells contribute to the avoidance of autoimmunity (an immune reaction against healthy cells).
Under “non-dangerous” conditions, Langerhans cells encourage the activation and proliferation of T regulatory (Treg) cells in the epidermis (i.e., when there is an absence of pathogenic agents). Treg cells release cytokines that enhance immunological tolerance and inhibit immune activation that is unneeded and possibly damaging.
However, in the existence of a pathogen, Langerhans cells boost effector T cell activation while limiting Treg cell activation. They activate effector cells (aid and cytotoxic T cells) to launch an immune response against the invader and rid the skin of infections.
What is Langerhans Cell Histiocytosis (LCH)?
Langerhans Cell Histiocytosis (LHC) is a rare cancer characterised by the rapid proliferation and replication of abnormal Langerhans cells. This results in an accumulation of Langerhans cells in several locations, including the skin, mouth, lymph nodes, thymus, eyes, endocrine system, central nervous system (CNS), liver, spleen, lungs, and bone marrow. Langerhans cell abnormal growth may result in tissue injury and lesions in affected body locations, with symptoms differing according to the affected body part.
LCH affects the bones in around 80% of patients (usually the skull or the arm or leg bones). This results in discomfort and swelling, as well as the possibility of fractured bone. LHC is also proven to have an effect on the skin. It causes rashes, pimples, and blisters that may range from minor to severe. In addition, LHC may alter hormone synthesis if the pituitary gland is damaged, which may cause infertility or delayed or missed puberty in adolescents and children. The thyroid may be affected by LHC, resulting in changes in the skin and hair texture, body temperature, and behaviour of the patient.