Langerhans cell
Also known as: epidermal dendritic cell, intraepidermal macrophage (old term)
Langerhans cells are antigen-presenting dendritic cells of the epidermis that capture antigens and migrate to regional lymph nodes to activate T cells; they contain characteristic Birbeck granules.
Overview
Langerhans cells form a network of dendrites among keratinocytes, mostly in the stratum spinosum, and make up ≈2–5% of epidermal cells. They are a specialised member of the mononuclear phagocyte family: in the steady state they derive from embryonic (yolk-sac and fetal-liver) precursors that colonise the epidermis before birth and self-renew locally, while after inflammation they are replenished from blood monocytes. They express CD1a (which presents lipid antigens), MHC class II, S100 and the C-type lectin langerin (CD207), which forms the rod-shaped, "tennis-racket" Birbeck granules seen by electron microscopy.
They sample antigens penetrating the barrier through dendrites that can reach between tight junctions. On activation they mature, upregulate CCR7 and co-stimulatory molecules and migrate via dermal lymphatics to the paracortex of the draining lymph node, where they present antigen to naive T cells. They are central to the sensitisation phase of allergic contact dermatitis and to skin immune tolerance. UV radiation depletes Langerhans cells, contributing to UV-induced local immunosuppression.
- Location
Mainly the stratum spinosum of the epidermis; also stratified squamous epithelia of the oral cavity, oesophagus, vagina and cervix.
Anatomy
- Histology
Not distinct on H&E (pale cells with indented nucleus); identified by CD1a, langerin (CD207) and S100 immunostaining or Birbeck granules on electron microscopy.
Function
- Capture and process antigens penetrating the skin
- Migrate to regional lymph nodes and present antigen to T cells
- Initiate type IV (contact) hypersensitivity and promote tolerance to commensals
- Present lipid antigens via CD1a
Clinical significance
Allergic contact dermatitis
Small haptens (nickel, poison ivy urushiol, fragrances, hair dyes) bind self-proteins, are carried to lymph nodes by Langerhans and dermal dendritic cells, and sensitise T cells; re-exposure triggers a type IV (delayed, T cell-mediated) hypersensitivity eczematous reaction 48–72 h later. Diagnosed by patch testing.
Langerhans cell histiocytosis
Clonal proliferation of Langerhans-type cells (often BRAF V600E-mutant) causing lytic skull lesions, seborrhoeic-like rash, diabetes insipidus and exophthalmos; lesional cells are CD1a+/langerin+ with Birbeck granules.
Test yourself
On electron microscopy, a dendritic cell in the stratum spinosum contains rod-shaped "tennis-racket" granules. What is this cell?
- Melanocyte
- Merkel cell
- Langerhans cell
- Mast cell
Answer: Langerhans cell
Birbeck granules, formed by the lectin langerin (CD207), are characteristic of Langerhans cells, the antigen-presenting dendritic cells of the epidermis (also CD1a and S100 positive).
Compiled from standard anatomy and physiology references — see the Integumentary System sources. For education only; not medical advice.