Langerhans-Zellen

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Section of skin showing large numbers of dendritic cells (Langerhans cells) in the epidermis. (M. ulcerans infection, S100 immunoperoxidase stain.)

The representation of Langerhans cells in the Cell Ontology. A portion of the Cell Ontology is shown with ovals corresponding to cell types defined in the ontology and arrows corresponding to relations between those cell types. Langerhans cell is represented by a yellow oval; blue arrows correspond to is_a relations, and orange arrows correspond to develops_from relations. Only a subset of Langerhans cell parent types are included in the figure.

Langerhans cells are dendritic cells (antigen-presenting immune cells) of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominent in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as in the oral mucosa, foreskin, and vagina. They can be found in other tissues, such as lymph nodes, particularly in association with the condition Langerhans cell histiocytosis (LCH).

History

The Langerhans cell is named after Paul Langerhans, a German physician and anatomist, who discovered the cells at the age of 21 while he was a medical student. Because of their dendritic nature, he mistakenly identified the cells as part of the nervous system.

Funktion

In skin infections, the local Langerhans cells take up and process microbial antigens to become fully functional antigen-presenting cells.

Generally, dendritic cells in biological tissue are active in the capture, uptake and processing of antigens. Once dendritic cells arrive in secondary lymphoid tissue, however, they lose these properties while gaining the capacity to interact with naive T-cells.

Langerhans cells derive from the cellular differentiation of monocytes with the marker "Gr-1" (also known as "Ly-6G/Ly-6C"). This differentiation requires stimulation by colony stimulating factor (CSF)-1. They are similar in morphology and function to macrophages.

Langerin is a protein found in Langerhans cells, and other types of dendritic cells.

Clinical significance

LCH

In the rare disease Langerhans cell histiocytosis (LCH), an excess of these cells is produced. This can cause damage to skin, bone and other organs.

HIV

Former hypothesis

Kawamura et al. (2005) suggested Langerhans cells may be initial cellular targets in the sexual transmission of HIV, and as a target, reservoir, and vector of dissemination.

Hussain & Lehner (2005) observed Langerhans cells have been observed in foreskin, vaginal, and oral mucosa of humans; the lower concentrations in oral mucosa suggest that it is not a likely source of HIV infection relative to foreskin and vaginal mucosa.

Present view

On March 4, 2007 the online Nature Medicine magazine published the letter "Langerin is a natural barrier to HIV-1 transmission by Langerhans cells." One of the authors of the study, Teunis Geijtenbeek, said that "Langerin is able to scavenge viruses from the surrounding environment, thereby preventing infection" and "since generally all tissues on the outside of our bodies have Langerhans cells, we think that the human body is equipped with an antiviral defense mechanism, destroying incoming viruses."