Adhesion Molecules (including diseases) Flashcards
What is the function of the BMZ?
Adhere the epidermis to the dermis
What stains can be used to highlight the BMZ?
PAS - purplish
What is the basement membrane?
The thin line seen with light electron microscopy between the epidermis and the dermis
What is the basal lamina?
Dense sheet-like structure seen with electron microscopy which is secreted by epidermal keratinocytes
Traditionally composed of lamina lucida and lamina densa
What is the basement membrane zone?
The complex structure which can be seen with electron microscopy and spans the space between the base of the basal keratinocytes to the underlying dermal matrix.
Consists of:
- Intermediate filaments
- Hemidesmosomes
- Anchoring filaments
- Lamina densa
- Anchoring fibrils
What are the four levels that the BMZ can be divided into when viewed via electron microscopy?
Basal keratinocytes
Lamina lucida (artifact of processing)
Lamina densa
Sublamina densa/superficial papillary dermis
What is the lamina lucida?
Traditionally one of the layers of the basal lamina but is really an artifact caused by dehydration fixation for electron microscopy - is not present when processed with chemical fixation
More historical than scientific significance
Contains extracellular domains of Col XVII, a6b4 integrin and CD151 as well as anchoring filaments (laminin-332)
What are the functions of the cytoskeleton within the basal keratinocytes?
- Structural support
- Cell movement
- Intercellular transport
- Anchor cells
What types of filaments compose the cytoskeleton within the basal keratinocytes?
1) Microfilaments (7nm diameter)
2) ** Intermediate filaments (10 nm diameter)
- most important for the BMZ
3) Microtubules (25 nm diameter)
What are the molecules that keratin intermediate filaments bind to in the BMZ?
- Plectin
- BPAG1e
Both part of the plakin family
Describe the structure of a hemidesmosome.
Two plaque structure (inner and outer) within basal keratinocytes
Composed of at least 5 distinct molecules
- BPAG1e (inner)
- Plectin (inner)
- α6β4 integrin (outer, extends into lamina lucida - transmembrane)
- collagen XVII (outer, extends into lamina lucida -transmembrane)
- CD151
What is BPAG1e aka BP230?
230 kDa, found in the inner plaque of hemidesmosomes
Dumb-bell shaped with 3 domains:
Belongs to plankin family
bindings to b4-subunit of a6b4 integrin, intermediate filaments, COL XVII
Functions:
- structural integrity
- signaling and regulation of cell polarity and migration
- not required for hemidesmosome/BMZ assembly
- no associated genetic disease?
What is plectin?
450-533 kDa, found in the inner plaque of hemidesmosomes
Belongs to the plankin family
Has 4 domains
Bind to keratin intermediate filaments and β4 of α6β4
Interacts with all keratinocyte cytoskeletal proteins
Functions:
- Structural integrity
- Scaffold for signaling molecules
What is α6β4 integrin?
Transmembrane protein
Found in the outer plaque and extends into lamina lucida
a3b1 also exists and is found elsewhere, not big in the BMZ
Alpha chain has 6 domains, shorter, small intracytoplasmic portion
*multiple calcium binding sites
- binds collagen XVII and CD151
Beta chain has 7 domains, longer
- binds to laminin-332, intermediate filaments, BPAG1e, collagen XVII, and plectin
Functions of integrins:
- Structural integrity
- Epidermal adhesion, proliferation, and differentiation
- B1 subunit is important for hair growth and wound healing
What is collagen XVII aka BP180?
Transmembrane protein
180 kDa, outer plaque extending into lamina lucida and lamina densa
Is cleaved extracellularly into 120 kDa LAD-1 and 97 kDa LABD97 which are associated with linear IgA bullous dermatosis
Has 4 domains which can be visualized as a globular head, rigid central rod region and flexible tail
- intracellular aspect (head) binds to plectin, BPAG1e, and a6b4 integrin (b4)
-extracellular NC16A domain (tail) binds to α6β4 integrin (α6) and laminin-332
Functions:
- structural integrity
- basal cell migration and adhesion
- enamel formation
What is CD151?
DO NOT WORRY ABOUT THIS TOO MUCH - NOT IN BIZIKOVA’S LECTURE
29-32 kDA, found in outer plaque of hemidesmosome
6 functional domains
- amino and carboxyl ends are both found within the basal keratinocyte membrane
- long extracellular loop which interacts with α6β4 integrin (a6)
Will cluster and interact with each other and integrins to form a tetraspanin web
What are anchoring filaments?
~800 nm wide structures seen within the lamina lucida on electron microscopy
-composition is controversial but may include laminin-332** (believed to be the main component) and Col XVII +/- a6b4 integrin, CD151, or laminin-311
Describe laminin-332 (old name laminin-5)
410 kDa
Large glycoproteins composed of 3 chains (a, b, y) connected with disulfide bonds - name come from the numbers associated with the chains
Forms a t shape
Secreted by keratinocytes as a precursor that then assembles
alpha 3 arm binds α6β4 integrin
beta 3 arm binds Col VII and other laminins
gamma 2 chain binds Col IV, Col VII, Col XVII and perlecan
Other laminins (511 and 311) are also found in the BMZ but this is considered the prototype
Functions:
- structural integrity
- embryogenesis
- tissue morphogenesis
- regulation of proliferation and differentiation
- tumorigenesis
What is the lamina densa?
The electron dense zone seen on electron microscopy below the lamina lucida
Contains collagen IV, laminin-332, nidogen, and perlecan
Also contains portions of a6b4 integrin
Is made of lattices of collagen IV molecules (majority) and others of laminin-332 molecules
What is collagen IV?
Made in the rough ER and secreted into the basement membrane
Resembles pro-collagen because has amino and carboxyl termina
Triple helical structure with 3 domains (like all collagens)
Self assembles into 3 dimensional hexagonal lattice structures of tetramers
There are a variety of formations due to the alpha chains which can be found in various places, one variant found just in the glomerulus
Within the lamina densa
Complex binding with other BMZ components (laminin-332, perlecan, nidogen, fibronectin, collagen VII)
Functions:
- structural integrity
- tumorigenesis
Describe nidogen 1 and 2?
1500-200 kDa, found in the lamina densa
Sulfated monomeric glycoprotein with 4 domains, dumb-bell shaped
Within the lamina densa
- One end binds Col IV and perlecan
- Other end binds laminin 311
Functions:
- structural integrity
- embryogenesis
- tumorigenesis
Describe perlecan
A heparan sulfate proteoglycan found in the lamina densa
680-770 kDa
Central core has 5 domains
- bind to nidogen, collagen IV and other less common molecules
Functions:
- negative charge for the basement mebrane
- structural integrity
- permeability barrier
- regulation of angiogenesis, etc
- cellular adhesion
- epidermal morphogenesis
- tumorigenesis
Describe the anchoring fibrils
Found in the sublamina densa/superficial papillary dermis
Semi-circular loops of collagen VII which resemble Velcro
The lattices of the lamina densa weave through them
Describe collagen VII
290 kDA triple helical molecules, found in the lamina densa and sublamina densa
Makes up anchoring fibrils
Has 3 main domains
Self-assembles into antiparallel dimers with carboxyl terminal ends touching (cystine residues creating disulfide bonds)
- this NC2 domain is cleaved by BP1 during creation of the anchoring fibrils
NC1 domains(amino terminal) interacts with Laminin-332 and Collagen IV
Function: loops around dermal collagen
What are the functions of intermediate filaments?
- Structural and mechanical cellular integrity
- Organization of cytoplasmic architecture
- Intracellular signaling
- Regulation of transcription
What are the congenital diseases associated with intermediate keratin filaments?
Epidermolysis bullosa simplex (EBS)
- KRT5 in cattle
- KRT14 in cats
What are the auto-immune diseases associated with intermediate keratin filaments?
Not confirmed in veterinary medicine
Which keratin intermediate filaments are associated with the BMZ?
K5, K14
Coded by genes KRT5 and KRT14
What congenital diseases are associated with plectin?
Epidermolysis bullosa simplex
- Eurasier dog
- one foal with signs of EBS and laminitis
What is epidermolysis bullosa simplex in dogs?
Congenital autosomal recessive mutation in PLEC (plectin)
- reported in Eurasier dogs
- clinical signs by 20 days of age
- blistering/ulcers on haired skin, footpads (sloughing), and oral cavity
- most are euthanized
*UPenn can test for it
What autoimmune diseases are associated with plectin?
Not confirmed in veterinary medicine
What congenital diseases are associated with BPAG1e?
None confirmed in veterinary medicine
What autoimmune diseases are associated with BPAG1e?
- Bullous pemphigoid, rare, dogs
- Mucous membrane pemphigoid, rare, dogs
What congenital diseases are associated with a6b4 integrin?
Junctional epidermolysis bullosa (JEB)
- ITB4 in cattle and sheep
What autoimmune diseases are associated with a6b4 integrin?
Not confirmed in veterinary medicine
What congenital diseases are associated with collagen XVII?
Junctional epidermolysis bullosa in two cats
What autoimmune diseases are associated with collagen XVII?
- Bullous pemphigoid (major target = NC16A domain) in dog, horse, cat, pig
- Mucous membrane pemphigoid in dogs, cat
- Linear IgA bullous diseases in dogs (due to LAD-1)
What congenital diseases are associated with laminin 332?
Junctional epidermolysis bullosa (JEB)
- LAMA3 in dog, horse, and cow
- LAMB3 in a dog
- LAMC2 in draft horses, cow and a sheep
What autoimmune diseases are associated with laminin 332?
- Mucous membrane pemphigoid (dog, cat)
- Aquired JEB (dogs)
- Mixed subepidermal blistering skin disease (dogs along with VII)
What congenital diseases are associated with collagen IV?
COL4A5 in a Samoyed (Alport syndrome, early onset renal failure)
COL4A4 in an English Cocker (autosomal recessive nephropathy)
What autoimmune diseases are associated with collagen IV?
Not recognized in veterinary medicine
What diseases are associated with nidogens?
Congenital:
- not recognized in veterinary medicine
Autoimmune:
- not recognized in veterinary medicine
What diseases are associated with perlecan?
Congenital:
- not recognized in veterinary medicine
Autoimmune:
- not recognized in veterinary medicine
What congenital diseases are associated with collagen VII?
Dystrophic epidermolysis bullosa (cattle and dogs)
- retrievers have a mild variant
What autoimmune diseases are associated with collagen VII?
- Epidermolysis bullosa acquistita (dog)
- Type I bullous systemic lupus erythematosus (one dog)
What genes are associated with the intermediate filaments in the BMZ?
KRT5, KRT14
What gene is associated with plectin?
PLEC1
What gene is associated with BPAG1e
BPAG1 (DST)
What genes are associated a6b4 integrin?
ITGA6, IGB4
What gene is associated with collagen XVII?
COL17A1
What genes are associated with laminin-332?
LAMA3, LAMB3, LAMC2
What genes are associated with collagen IV?
COL4A1 to COL4A6 (6 different alpha chains)
What genes are associated with nidogens?
NID1, NID2
What gene is associated with perlecan?
HSPG2
What gene is associated with Collagen VII?
COL7A1
What species has MMP been reported in and what is the age predilection?
Dogs (most common AISBD), human, cat
Breed predilection: GSD
Age predisposition: middle-aged
What are the clinical signs associated with MMP?
Distribution: mucocutaneous junctions, mucosa, infrequent haired skin
Lesions: tense vesicles (rare), deep erosions/ulcers, infrequent scarring
Which are the antigens are associated with mucous membrane pemphigus?
Immunologically heterogenous
Major antigen: Collagen XVII
Minor antigens: laminin-332, BPAG1e/BP230
What are the histopathologic findings associated with mucous membrane pemphigoid?
Level of split: lamina lucida
Histopathology: subepidermal vesiculation +/- minimal inflammation in vesicle
Variable non-inflammatory to perivascular dermal inflammation
May have lichenoid pattern because it is a mucocutaneous junction
Superficial dermal fibrosis
PAS or col IV stain on the dermal side
What is the immunopathology staining pattern of MMP?
IgG >C3, IgM, IgA at basement membrane
- higher than reported in ppl, maybe because it has been needed for publications
Salt split staining can be epidermal (most cases), dermal or both sides
What is the treatment of MMP?
No spontaneous remission
Many achieve remission, may flare
Monotherapy or combined
- Prednisone/lone
- tetracycline or doxycycline and niacinamide
- ciclosporin
- azathioprine
- chlorambucil
- mycophenolate mofetil
- dapsone
Monotherapy with glucocorticoids reported as least successful, tetracyclines as most
1/4 cats was able to have drug withdrawn
Which species has epidermolysis bullosa acquisitia (EBA) been reported in and at what age does it typically occur?
Dogs with Great danes being predisposed (over 1/2)
- Young, almost half of dogs reported developed lesions by 1 yr of age
*may be a genetic predisposition
Other species: human
- a childhood form is reported but mostly occurs in older adults
What are the clinical signs associated with epidermolysis bullosa acquisitia (EBA)?
Skin lesions: erythematous macules and papules; tense vesicles; deep erosions/ulcers
- often have pain and sometimes pruritus
Distribution: haired skin, footpads, and mucosae/mucocutaneous junctions
- footpad sloughing is frequent
Usually have fever, lethargy, lymphadenopathy and anorexia
Most would fall into “BP-like EBA variant” in the human naming system
What are the immunopathology associated with epidermolysis bullosa acquisitia (EBA)?
Major antigen: Collagen VII (NC1 domain)
Minor antigens: nd
IgG
What are the histopathologic findings associated with epidermolysis bullosa aquisita (EBA)?
Level of split: sublamina densa
Histopathology:
- subepidermal vesiculation with no to variable amounts of neutrophilic inflammation +/- fibrin or minor hemorrhage
- vacuolation and rowing of neutrophils and/or histiocytes occurs just below the BMZ
- Superficial dermal perivascular to interstitial dermatitis
What is the treatment for epidermolysis bullosa acquisitia (EBA)?
No spontaneous remission
Some may be euthanized (more so in the past)
Current success in 2-3 months with immunosuppression
- oral glucocorticoids
- various non-steroidal immunosuppressants (azathioprine, mycophenolate mofetil, etc.)
- colchicine is used in people and was successful for some dogs
Almost half of the dogs were able to discontinue medications
What species has bullous pemphigoid been reported in and what is the age predisposition?
Dog breed disposition: nd but maybe dachshund and GSD
Other species: human, cat, horse, (Yucatan) pig, possibly a macaque
Relatively rare
May be more mild in cats
May be worse in horses
Age predisposition: middle-age
What are the clinical lesions associated with bullous pemphigoid?
Skin lesions: erythematous macules and papules; tense vesicles; deep erosions/ulcers
Distribution: haired skin esp in pressure points but (footpads are rarely affected) and mucosae/mucocutaneous junctions
Usually healthy except horses are usually systemically unwell
What are the antigens associated with bullous pemphigoid?
Major antigen: Collagen XVII
Minor antigens: BPAG1e/BP230
What is the immunopathology of bullous pemphigoid?
Tissue-bound IgG and IgM autoantibodies along the BMZ
Circulating IgG, predominantly IgG1
Circulating IgE targeting BMZ (60%)
What are the histopathologic findings associated with bullous pemphigoid?
Level of split: lamina lucida
Histopathology: subepidermal vesiculation +/- eos, neuts, fibrin
- Eos in the superficial dermis
- IgG, IgM, or IgA and/or complement deposited at the BMZ
What is the treatment for bullous pemphigoid?
Spontaneous remission reported in 1/7 dogs
Immunosuppression induced complete remission
- glucocorticoids
- oclacitinib
- pred + azathioprine
- pred + pentoxifylline
- doxycycline and niacinamide
40% of dogs were able to stop medications
*most horses were euthanized due to poor response or side effects of medications
What species are reported to have junctional epidermolysis bullosa aquisita (JEBA) and what age is predisposed?
Dog breed disposition: nd (rare and only described in 5 dogs)
Other species: single human case with same features
Age predisposition: nd (6mo to 8yr, median 2.5)
What are the clinical signs associated with junctional EBA?
Skin lesions: erythema, vesicles, deep erosions/ulcers
Distribution: haired skin (pinnae, axillae/abdomen, footpads) and mucosae/mucocutaneous junctions
- footpad sloughing is frequent
May or may not be systemically ill
What is the immunopathology of Junctional EBA?
Major antigen: Laminin-332
Minor antigens: nd
IgG> C3, IgA
What is the histopathology associated with Junctional EBA?
Level of split: lamina lucida
Histopathology: subepidermal vesiculation +/-neutrophilic inflammation +/- eos
- potential superficial dermal perivascular to interstitial inflammation
How do you treat Junctional EBA?
Immunosuppression
- may end up being euthanized due to side effects or incomplete remission
- may be able to taper and stop medications
Which species has mixed AISBD been reported in and what is the age predilection?
Dog
- breed disposition: nd
- Age predisposition: young (2-4 yrs)
*But there have only been 3 cases
Other species: humans (different nomenclature)
What is the clinical presentation of mixed AISBD?
Skin lesions: erythema, tense vesicles and bullae, deep erosions/ulcers
Distribution: haired skin (concave pinnae, trunk; footpad sloughing is rare) and mucosae/mucocutaneous junctions
What is the immunopathology of mixed AISBD?
Major antigen: Collagen VII (like EBA) and laminin-332 (like JEBA)
Minor antigens: nd
IgG, IgA, C3
What are the histopathologic signs associated with mixed AISBD?
Level of split: lamina lucida
Histopathology: microscopic subepidermal vesiculation with mixed neutrophilic eosinophilic inflammation
What is the treatment for mixed AISBD?
Immunosuppression
Unknown how it works since all dogs were lost to follow up or euthanized due to treatment cost
What species has Linear IgA Disease (LAD) been reported in and what is the age predilection?
Dog breed disposition: nd
- only 2 reported, one was 3 and other was 4
Other species: human
- biphasic in young children and older adults
What is the clinical presentation of Linear IgA Disease (LAD)?
Skin lesions: erythema, vesicles, deep erosions/ulcers
Distribution: mucosae and haired skin (ears, nasal planum, footpad)
In humans it frequently looks like a “string of pearls” hence the name linear
What is the immunopathology of Linear IgA Disease (LAD)?
IgA (+/− IgG) reactivity against soluble antigens of collagen XVII cleavage products (LAD-1)
What are the histopathologic findings of Linear IgA Disease (LAD)?
Level of split: lamina lucida
Histopathology: microscopic subepidermal vesiculation +/- minimal neutrophilic inflammation
What is the treatment for LAD?
Unknown in dogs
Vancomycin is a common trigger in people so discontinue the drug
For spontaneous in people
- first line = sulfones (ex. dapsone) or colchicine
- second line = combination of glucocorticoids and non-steroidal immunosuppressant
What is pemphgoid gestastionis?
An AISBD that occurs in pregnant animals
Reported in 1 dog, not published
Other species: human (2nd or 3rd trimester most common)
What is are the lesions associated with pemphgoid gestastionis?
Skin lesions: vesicles, erosions/ulcers
Distribution: mucosae and haired skin (ears, nasal planum, periareolar, footpad)
What is the immunopathology of pemphgoid gestastionis?
SIgG, IgM, and C3 probably against Collagen XVII/BP180 suspected
What is the treatment for pemphgoid gestastionis?
The one dog had an ovariohisterectomy
Most people spontaneously recovery 4-14 weeks post-partum
What species has bullous systemic lupus erythematosus been reported in?
One dog