Section of skin showing large numbers of dendritic (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. From Masci et al., 2009.^[1]

Langerhans cells are dendritic cells^[2] in the epidermis,^[3] containing large granules called Birbeck granules. They are normally present in lymph nodes and other organs, including the stratum spinosum layer of the epidermis. They can be found elsewhere, particularly in association with the condition histiocytosis.

[edit] 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.^[4] He mistakenly identified the cells as part of the nervous system.^[5]

[edit] Function

On infection of an area of skin, the local Langerhans cells will take up and process microbial antigens to become fully-functional antigen-presenting cells.

Generally, dendritic cells in 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 are derived from the cellular differentiation of monocytes with the marker "Gr-1" (also known as "Ly-6G/Ly-6C"). The differentiation requires stimulation by colony stimulating factor (CSF)-1.^[6] They are similar in morphology and function to macrophages. ^[7]

Langerin is a protein found in Langerhans cells,^[8] and other types of dendritic cells.^[9]

[edit] Clinical significance

[edit] LCH

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

[edit] HIV

Langerhans cells capture HIV-1 virions by way of Fc receptor binding to antibody-coated virus. Langerhans cells act as reservoirs for the HIV-1 virus, serving as a site of replication when T-cells become depleted (Robbins Pathology).

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.^[10]

On March 4, 2007 the online Nature Medicine magazine published the letter "Langerin is a natural barrier to HIV-1 transmission by Langerhans cells."^[11] Teunis Geijtenbeek, one of the authors of the study, 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."^[12]

[edit] See also

• Langhans giant cell

[edit] References

[edit] External links

• Langerhans Cell Histiocytosis at eMedicine
• Illustration at trinity.edu
• Birbeck granules at djo.harvard.edu
• MeSH Langerhans+Cells