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MSS > Basement Membrane Zone > Flashcards

Basement Membrane Zone Flashcards

1
Q

what is the basement membrane zone?

A

a complex structure that provides dermo-epidermal adhesion and regulates many important processes such as cell differentiation, motility, and the transmission of extracellular signals.

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2
Q

what do the ultrastructures of the BMZ include?

A 
Hemidesmosomes (BP 230, BP 180)
Lamina lucida (BP 180)
Lamina densa (laminin 332, collagen IV)
Sublamina densa (collagen VII)
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3
Q

what are hemidesmosomes?

A

small structures on the inner surface of basal keratinocytes that are composed of many structural proteins. They are similar in form to desmosomes when visualized by electron microscopy.

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4
Q

how are hemidesmosomes different from desmosomes?

A

While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix

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5
Q

what is Bullous Pemphigoid Antigen 1?

A

BP 230. it belongs to the plakin family of proteins, has cytoplasmic localization and is important for the organization of the cytoskeletal architecture

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6
Q

what is bullous pemphigoid antigen 2?

A

Now referred to as type XVII collagen, BP 180 is a transmembrane protein connecting basal keratinocytes and cytoskeleton (via BP 230) to dermal collagen VII (via laminin 332).

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7
Q

what is the second layer of the BMZ? where?

A

Immediately underlying hemidesmosomes is a thin structure known as the lamina lucida (LL). Newer techniques using high-pressure freeze substitution electron microscopy suggest that LL may be an artifact of tissue preparation and dehydration.

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8
Q

what is the lamina densa composed of?

A

mostly type IV collagen and laminins

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9
Q

what is type IV collagen?

A

this is one of the most abundant collagenous glycoproteins of the BMZ, comprising more than half of its mass. it is a heteropolymer which polymerizes into a triple helix and lattice formation

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10
Q

the most abundant non-collagenous BMZ glycoproteins?

A

laminins

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11
Q

he key BMZ laminin is?

A

laminin 332

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12
Q

Laminin-332 binds to?

A

this binds to the transmembrane protein of the hemidesmosome integrin α6β4 using the G domain on its α3 chain, as well as to type VII collagen using its NC-1 domain, bridging the BMZ.

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13
Q

what is type VII collagen made of?

A

large protein, composed of three identical alpha-chains that form anchoring fibrils

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14
Q

what is the role of type VII collagen?

A

it is necessary to maintain epidermal-dermal cohesion, since it binds to both type I and type IV collagens, which further allows the type VII collagen molecule to join the lamina densa to the papillary dermis

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15
Q

what is the process of a routine biopsy? what does it determine?

A

taken from the edge of blister and processed by regular histologic (hematoxylin & eosin, H&E) staining to determine blister level and inflammatory infiltrate.

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16
Q

what does DIF do?

A

helps detect molecules such as immunoglobulins and complement (C3) within biopsy specimens.

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17
Q

where are DIF samples taken from?

A

The skin samples are taken from perilesional skin.

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18
Q

what does DIF detect? how?

A

Commercially-available fluorescein-conjugated antibodies against human immunoglobulins or complement are used to detect in-situ (in the patient skin) deposits of immunoreactants under the fluorescence microscope.

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19
Q

what does IIF detect?

A

detects circulating antibody against BMZ in the patient’s serum

20
Q

what are the two steps of IIF?

A

In the first step, the patient serum is applied to a foreign substrate such as normal human skin (sometimes with an artificial split at the level of the lamina lucida created by salt), monkey esophagus, or rodent bladder. The circulating antibodies from the sera bind to the BMZ antigen in the substrate. In the second step, the antibody antigen complex is detected by fluorescein-conjugated antibody and visualized under the fluorescence microscope.

21
Q

what is ELISA used for? why is it helpful?

A

used as an initial screen for detection of patient’s circulating
autoantibodies. Based on the principle of antibody-antibody interaction, this test allows for easy visualization of results and can be completed in a short period of time.

22
Q

what type of IgG is used in DIF

A

tissue bound IgG

23
Q

what type of IgG is used in IIF?

A

circulating IgG

24
Q

what are the inherited blistering disorders of the BMZ called/group name?

A 
epidermolysis bullosa. 4.
 Bullous pemphigoid
 Mucous membrane pemphigoid
 Epidermolysis bullosa acquisita
 Pemphigus vulgaris (discussed in the Epidermis section)
25
Q

what is the most common autoimmune bullous dermatosis?

A

bullous pemphigoid

26
Q

BP occurs in whom? how does it appear?

A

occurs primarily in the elderly. BP starts with pleomorphic clinical features, eg highly pruritic urticaria without blistering. then tense blisters with serous or rarely even hemorrhagic content appear in phases. blisters are extremely stable

27
Q

why are the BP blisters stable?

A

in contrast to the pemphigus group of diseases, the roof of the blister consists of the entire epidermis

28
Q

what are the autoantibodies directed against?

A

antibodies are directed against BP antigen 1 (BP 230) and BP antigen 2 (BP 180), causing subepidermal blisters

29
Q

what does DIF show? IIF? ELISA?

A

DIF shows linear deposits of IgG and C3 along the BMZ.
IIF usually shows linear staining of on the epidermal side of salt-split skin.
The BP 180 and BP 230 ELISA show positive results correlating with the disease activity.

30
Q

BP treatment? outcomes?

A

Less severe cases can be treated with high potency steroids. Oral steroids and other immunosuppressants are used for severe disease with caution due to potential side effects in the elderly population. better prognosis than PV.

31
Q

who does Mucous Membrane Pemphigoid affect? what do they get?

A

predominantly affects older people and is characterized by recurrent blistering of mucous membranes, but also the skin. Patients with this disorder develop scars, strictures, synechiae, and in 20% of cases, blindness.

32
Q

what are the antibodies formed in MMP?

A

majority of patients have antibodies against BP 180, but some patients have antibodies targeting BP 230, integrin β4, and laminin 332.
in a subtype of MMP, anti-laminin 332 (epiligrin) pemphigoid, an association with malignancies has been reported in 30 % of cases; thus appropriate cancer screening examinations should be performed.

33
Q

what does DIF in MMP show? IIF?

A

DIF in MMP shows linear deposits of IgG and C3 along the BMZ. The IIF shows linear staining of epidermal, dermal and epidermal, or dermal (in the case of anti-laminin 332 MMP) side of salt-split skin substrate.

34
Q

what is EBA?

A

epidermolysis bullosa acquisita. rare autoimmune bullous dermatosis. Even slight trauma elicits blistering and erosions of the skin.

35
Q

EBA sites? results in?

A

mechanically-stressed areas such as hands, feet, elbows and knees. Healing of lesions leaves atrophy, milia, scars, and pigmentation disorders. Severe cases characterized by fibrosis of hands and feet. Nail dystrophy possible. often involvement of the oral mucosa in the form of hemorrhagic erosions.

36
Q

what is the EBA target antigen?

A

target antigen is type VII collagen.

37
Q

what does DIF show? IIF? ELISA?

A

DIF shows deposits of IgG and C3 along the BMZ. The IIF shows staining of dermal side of salt-split skin. Commercially-available ELISA testing is not available.

38
Q

what is epidermolysis bullosa (EB)?

A

Mutations in the genes encoding BMZ proteins result in the group of inherited skin fragility disorders known as EB.

39
Q

what does the absence of malfunction of these proteins lead to?

A

erosions and blisters after minimal mechanical trauma. broad spectrum of skin finding, depending on disease subtype. mutations in 10 different genes have been identified in different subtypes of EB.

40
Q

what are the targeted proteins in EB?

A

Targeted proteins include keratins 5 and 14, plectin, collagen types VII and XVII, α6β4 integrin, and laminin 332.

41
Q

what is epidermolysis bullosa simplex?

A

typically inherited in an autosomal dominant manner. The target proteins are keratins 5 and 14, which are present in basal keratinocytes

42
Q

what is junctional EB?

A

typically inherited in an autosomal recessive manner. The target proteins are laminin 332 and BP 180 at the BMZ.

43
Q

Dystrophic EB is?

A

inherited in both an autosomal dominant and recessive manner. The target protein is type VII collagen of the dermis.

44
Q

pemphigus vulgaris antigen?

A

desmoglein 1,3

45
Q

herlitz epidermolysis bullosa antigen?

A

laminin 332

46
Q

mucous membrane pemphigoid antigen?

A

laminin 332

MSS (28 decks)

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