Epithelium Answers 169Hemidesmosome Increased stability Link intermediate
of epithelia on filaments in the
extracellular cell to the ECM
matrix (ECM) through integrins
rather than cadherins
Communicating Gap junction Selective Connexons in
(nexus) communication hexameric
in the form of arrangement with
diffusible central pores in
molecules adjacent cells
between 1 and align
1.5 kDClassification Type Function Interactions84.The answer is c.(Kasper, pp 311–312. Junqueira, p 366. Kierszenbaum, pp
16, 35, 307. Alberts, p 1072.)In pemphigus vulgaris, autoantibodies to
desmogleins (a member of the cadherin protein family) result in disruption of
the macula adherens (desmosomes). The desmogleins are the transmembrane
linker proteins of the desmosome. Specific desmogleins are the target of the
autoantibodies in different forms of the disease. Cadherins are Ca^2 +–depen-
dent transmembrane linker molecules essential for cell-cell contact, so their
disruption in pemphigus leads to severe blistering of the skin because of dis-
rupted cell-cell interactions early in the differentiation of the keratinocytes
(epidermal cell) and excessive fluid loss. The other parts of the junctional
complex: zonula occludens (answer b)and gap junctions (answer d)are
not affected in pemphigus. The connections to the basal lamina, hemidesmo-
somes(answer a),as well as the basal lamina itself, are not part of the etiol-
ogy of pemphigus. This is in contrast to bullous pemphigoid (BP), where the
BP antigen causes the separation of the epithelium from the basal lamina. Cad-
herins are also critical molecules in the maintenance of the zonula adherens,
but the autoantibodies in pemphigus are specific to the desmogleins. Pemphi-
gus vulgaris, which is described in the clinical scenario, often begins as oral
lesions and subsequently appears cutaneously. The Nikolsky sign is positive
(pressure at the edge of a blister causes extension of the bulla into adjacent nor-
mal skin) in pemphigus, while in bullous pemphigoid the Nikolsky sign is neg-
ative. For more details on junctional complexes, see the table in the answer for
question 83. Also, see questions 197 and 199.