Hemidesmosome (BP180, BP230, integrin alpha-6 beta-4)
Adhesion & dermo-epidermal junction · BP180 / BP230 Integrin α6β4 Pemphigoid
The half-desmosome that clamps the basal keratinocyte to the basement membrane. Transmembrane BP180 (type XVII collagen) and integrin alpha-6 beta-4 reach into the lamina lucida to bind laminin-332, while BP230 and plectin tie the plaque to K5/K14 filaments inside the cell.
Traced from the start
- Stratum basale (germinativum)
- Hemidesmosome (BP180, BP230, integrin alpha-6 beta-4)
Detail
- Transmembrane
- BP180 (type XVII collagen), whose NC16A ectodomain is the immunodominant epitope, and integrin alpha-6 beta-4
- Intracellular plaque
- BP230 and plectin, linking to the basal keratinocyte keratin cytoskeleton
- Extracellular partner
- Laminin-332, the core of the anchoring filaments crossing the lamina lucida
- Failure mode
- The whole epidermis lifts off intact, so blisters are tense and Nikolsky is negative — the opposite of acantholysis
When it goes wrong
IgG against BP180 NC16A, often with anti-BP230 (bullous pemphigoid)
Elderly patient with intense itch for weeks before tense blisters appear on flexures and trunk; mucosa usually spared, Nikolsky negative, blood and tissue eosinophilia; direct immunofluorescence shows linear IgG and C3 along the basement membrane
Mutation in laminin-332 or integrin alpha-6 beta-4 (junctional epidermolysis bullosa)
Blistering from birth at the lamina lucida with periorificial granulation tissue; the Herlitz form is usually fatal in infancy
Anti-BP180 in pregnancy (pemphigoid gestationis)
Blistering starting periumbilically in the second or third trimester, with a risk of prematurity and transient neonatal blistering from transplacental IgG
Practise this structure
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