Langerhans cell

Langerhans cell is a type of dendritic cell found in the epidermis, the outermost layer of the skin. Named after the German physician Paul Langerhans, who first described them in 1868, these cells play a crucial role in the immune system, particularly in the body's response to external pathogens and in the process of inflammation.

Structure and Location

Langerhans cells are present in all layers of the epidermis and are most abundant in the stratum spinosum. They are also found in other tissues, such as the mucosa, particularly in the oral cavity, vagina, and foreskin. Morphologically, they are characterized by their large size, oval shape, and the presence of Birbeck granules, rod-shaped structures visible under an electron microscope.

Function

Langerhans cells are part of the body's first line of defense against pathogenic invasion. They are capable of phagocytosis, a process by which they engulf and destroy pathogens. Once a pathogen is internalized, Langerhans cells process the pathogen's antigens and present them on their surface to T cells, a type of white blood cell. This antigen presentation triggers an immune response, leading to the destruction of the pathogen.

In addition to their role in immune response, Langerhans cells are involved in the process of inflammation. They release cytokines and chemokines, signaling molecules that attract other immune cells to the site of infection or injury.

Clinical Significance

Abnormalities in Langerhans cells can lead to several diseases. Langerhans cell histiocytosis is a rare disorder characterized by an overproduction of Langerhans cells, leading to tissue damage and organ dysfunction. On the other hand, a decrease in the number of Langerhans cells is associated with certain skin conditions, such as psoriasis and eczema.

Langerhans cells also play a role in HIV infection. The virus can bind to these cells and be transported to the lymph nodes, where it replicates and spreads throughout the body.

See Also

• Dendritic cell
• Immune system
• Inflammation
• Langerhans cell histiocytosis