BMZ, adhesion molecules, AISBDs Flashcards
What is the keratin composition of intermediate filaments?
Keratin-5 (basic), keratin-14 (acidic)
Define intermediate filament
Connection between the keratinocyte nucleus to hemidesmosomes on the keratinocyte membrane. Responsible for structure of basal keratinocytes
What is the composition of the inner plaque of the hemidesmosome?
Plectin
BPAG1-e
What is the composition of the outer plaque of the hemidesmosome?
Integrin alpha6beta4
collagen XVII (cytoplasmic domain)
Define anchoring fibrils
Connections extending from lamina densa to collagen fibers in the dermis
What is the collagen composition of anchoring fibrils?
Collagen VII
Define integrins
Cell adhesion molecules that connect the extracellular matrix to the cytoskeleton
What family is BPAG1-e a member of?
Plakins
What autoimmune conditions in dogs may result from autoantibodies against BPAG1e?
Bullous pemphigoid, MMP
Which classes of adhesion molecules (CAMs) operate independent of Ca++?
integrins, IgCAMs
Which classes of adhesion molecules (CAMs) are dependent on Ca++?
cadherins, selectins
What class of adhesion molecules is present on leukocytes, allowing for leukocyte adhesion to the endothelium?
Integrins
What type of integrins bind leukocytes to the endothelium?
Beta2
What type of integrins bind T-cells to APCs?
Beta2
What beta2 chain is common to many integrins?
CD18
What is a primary role of beta3 integrins?
Clotting
What integrin on T-cells binds to ICAM-1 on APCs to allow for successful antigen recognition?
LFA-1
What integrin on endothelial cells is important for extravasation of leukocytes when bound?
ICAM-2 (bound by LFA-1 on neuts)
What does alpha6beta4 bind to extracellularly?
Laminin 332
In what layer(s) of the epidermis are integrins expressed?
Stratum basale only
What cell adhesion molecule is present on inflamed endothelial cells and binds VLA-4 to allow for generation of ROS?
VCAM-1 (CD106)
What are the classical type 1 cadherins?
E-cadherin, N-cadherin, P-cadherin
What cell types express N-cadherin?
Myocytes, neurons, fibroblasts
What are the classical type 2 cadherins?
VE-cadherin, M-cadherin
What cadherin becomes temporarily dysregulated to allow for diapedesis?
VE-cadherin
What is the major autoantigen in human PF?
Desmoglein-1
What is the major autoantigen in canine PF?
Desmocollin-1
What is the autoantigen in pemphigus vulgaris?
Desmoglein-3
Describe the locations of desmogleins 1-3 in the epidermis
Desmoglein-1: superficial epidermis
Desmoglein-2: basal layer
Desmoglein-3: deep epidermis
Name two major functions of selectins
- Mediate initial low-affinity adhesion of WBC to endothelium
- Lymphocyte homing
What cell types express P-selectin?
Endothelial cells, platelets
What structures within endothelial cells store P-selectin?
Weibel-palade bodies
What structures within platelets store P-selectin?
alpha granules
What activates P-selectin?
Histamine, thrombin
What cells express E-selectin?
Endothelial cells
What triggers activate E-selectin?
IL-1, TNF, LPS
What cells express L-selectin?
Leukocytes (NOT endothelial cells)
What dog breed is reported to be associated with canine leukocyte adhesion deficiency (CLAD)?
Irish Setters
Describe the pathogenesis of canine leukocyte adhesion deficiency
Single missense mutation in beta2-integrin subunit gene –> cysteine replaced by serine at AA36 –> disulfide bond disruption in CD18 leading to less WBC binding –> recurrent infections despite normal or high WBC counts
How would you diagnose CLAD?
PCR (can be done on oral swab)
What cow breed has been reported in bovine leukocyte adhesion deficiency (BLAD)?
Holstein
Describe the pathogenesis of BLAD
Point mutation in CD18 gene –> aspartic acid replaced by glycine –> dysfunctional integrin assembly and lack of WBC diapedesis
What are the 4 major types of adhesive structures in the epidermis?
Adherens junctions, desmosomes, tight junctions, hemidesmosomes
What histologic stain could be useful to highlight the BMZ?
PAS
Name the layers of the basement membrane zone
Basal keratinocyte –> basal lamina (lamina lucida + lamina densa) –> sublamina densa
Know the locations of various molecules in each layer of the BMZ
Define the location of hemidesmosomes
Found along the ventral aspect of the basal keratinocyte
Name the 4 components of a hemidesmosome
BPAG-1
plectin
integrin alpha6beta4
collagen XVII
What is the molecular target of epidermolysis bullosa simplex in cattle and dogs?
KRT5
What is the molecular target of epidermolysis bullosa simplex in cats?
KRT14
What is the molecular target of epidermolysis bullosa simplex in Eurasier dogs?
Plectin
What is the molecular target of junctional epidermolysis bullosa in cattle?
ITGA6 (integrin alpha6), ITGB4 (integrin beta4)
What is the molecular target of junctional epidermolysis bullosa in sheep?
ITGB4 (integrin beta4)
What would be considered the primary inflammatory cell infiltrate in bullous pemphigoid in dogs?
Eosinophils
What is the target of bullous pemphigoid in dogs?
NC16A domain of collagen XVII
What does PAS stain in the lamina densa?
Nidogen and perlecan (proteoglycans)
What component of the basement membrane zone forms a hexagonal meshwork/lattice?
Collagen IV (lamina densa)
What is the main molecular target of epidermolysis bullosa acquisita (EBA) in dogs?
Collagen VII (esp NC1 domain)
What is unique in regards to EBA compared to other acquired AISBDs in dogs?
Age of onset- EBA has young onset (1-2 years though puppies may be affected), other AISBDs have 5-6 year of age onset
The “floor” stains on indirect immunofluorescence on salt split mucosa. What is/are the most likely differential(s)?
EBA
JEBA
bullous SLE
MMP (can be roof or floor)
mixed AISBD
The “roof”/epidermal side stains on indirect immunofluorescence on salt split mucosa. What is/are the most likely differential(s)?
BP (others: MMP, linear IgA)
There is “mixed” staining on indirect immunofluorescence on salt split mucosa. What is/are the most likely differential(s)?
MMP (usually roof stains but can be both)
JEBA
A ragged, intracellular split occurs on PAS staining of a suspect AISBD. What is the most likely differential?
EB simplex (targets KIF)
What is the major autoantigen in MMP?
NC16A domain of collagen XVII (BPAG2)
–BPAG1e and laminin 332 also reported
What is the major autoantigen in canine JEBA?
Laminin 332
What antigens stain on the floor of salt-split skin?
Laminin 332, collagen IV, collagen VII
What antigens stain on the roof of salt-split skin?
K5, K14, plectin, BPAG1, BPAG2, integrin alpha6beta4
What is the most common AISBD in dogs?
MMP
What dog breed has a suspected genetic predisposition to EBA?
Great Dane (and less so GSP)