Flashcards in Small Animal Deck (109):
What sites contain Igs normally, and should therefore not be collected for immunofluorescence testing?
nasal planum of dogs and cats, footpads of dogs
What is Michel fixative?
fixative used for samples submitted for direct immunofluorescence testing. Samples can be held in this for up to 2 weeks. pH: 7.0-7.2
immunoperoxidase testing can yield false POSITIVE or false NEGATIVE results?
What are the phases of treatment as it relates to immune-mediated dermatoses?
(1) induction of remission, (2) transition, (3) maintenance, and (4) determining cure
Goal of Induction phase:
avoid bad side effects; can take days to weeks
goal of transition phase:
get to lowest effective dose, takes weeks to months
goal of maintenance phase:
maintain dose for duration of disease with monitoring to avoid adverse effects, takes 6 mos to years
goal determining cures:
stop drugs after complete remission has been maintained and observe for recurrence of disease; may take several attempts
Azathioprine is what kind of drug?
Synthetic modification of 6-mercaptopurine; antagonizes purine metabolism and interferes with DNA/RNA synthesis.
metabolized in the liver to 6-mercaptopurine and other active metabolites.
6-Mercaptopurine is then metabolized by three enzyme systems. 1) Xanthine oxidase and
2) thiopurine methyltransferase (TPMT) produce inactive metabolites. Humans and possibly dogs that have absent (homozygous) or low (het- erozygous) TPMT activity are more likely to experience myelo- suppression; cats have lower levels, making them more susceptible to toxicity
3) hypoxanthine phosphoribosyltransferase
What is azathioprine metabolized to and by which enzyme system?
Metabolized to 6-mercaptopurine (and other active metabolites)
-Xanthine oxidase and thiopurine methyltransferase (TPMT) produce inactive metabolites - if TMPT is low, can have more myelosuppression
what drugs do you NOT want to use with azathioprine?
what are potential side effects of azathioprine?
bone marrow suppression! hepatotoxicity (but rare, and usually in combo)
(CEG: as long as acting normal, and bilirubin not up, ok to see some liver values change)
anemia, leukopenia (lymphopenia**), demodicosis, thrombocytopenia, vomiting, hypersensitivity reactions (especially of the liver), pancreatitis (esp if also on steroids), elevated serum alkaline phosphatase concentrations, rashes, and alopecia, diarrhea (hemorrhagic) - most respond to drug reductions,
How long is the lag time for azathioprine?
There is often a lag phase, with clinical improvement occurring in 3 to 6 weeks
What are adverse effects of azathioprine in cats (and why should AZA NOT BE USED IN CATS)?
fatal leukopenia and thrombocytopenia)
what is chlorambucil?
alkylating agent derived from nitrogen mustard. Its cytotoxic effect is due to cross-linking of DNA
what are potential side effects of chlorambucil?
v/d, anorexia, alopecia and delayed hair growth after clipping have been reported, (poodles and Kerry blue terriers are reported to be at greater risk)
what's a potential side effect of cyclophosphamide?
STERILE HEMORRHAGIC CYSTITIS (30% of dogs on it for >2 mos), bladder fibrosis, teratogenesis, infertility, alopecia and poor hair growth, nausea, GI inflammation, bone marrow suppression
what is colchicine?
alkaloid that suppresses neu- trophil chemotactic and phagocytic functions via disruption of microtubule assembly and elongation, increasing cellular cyclic adenosine monophosphate (cAMP) levels and inhibiting lysosomal degranulation
-It also inhibits immunoglobulin secretion, interleukin (IL)-1 production, histamine release, and human leukocyte antigen (HLA)-DR expression.
-inhibits cell division during metaphase by interfering with sol-gel formation and the mitotic spindle.
What drugs should not generally be used with colchicine?
NSAIDs - concern with concurrent use and bone marrow suppression
don't use with azathioprine or chlorambucil
What is cyclophosphamide?
nitrogen mustard alkylating agent metabolized to agents that inhibit mitosis via interferring with DNA replication and RNA transcription and replication
what cell line is most sensitive to cyclophosphamide?
lymphocytes - especially b cells
suppresses antibody production
What is the MOA of mycophenolate mofetil?
=prodrug is antiproliferative agent mycophenolic acid (MPA) and specifically and reversibly inhibits inosine monophosphate dehydrogenase --> thereby inhibits purine (guanine) synthesis and prevents maturation of B and T lymphocytes
-inhibits de novo synthesis of purine
-suppresses T and B lymphocytes
-induces lymphocyte apoptosis
-induced dendritic cell maturation
-decreases IL-1 expression
-enhances expression of IL-1R antagonist
Mycophenolate mofetil has a synergitic effect with which other immune suppressive drug?
What are some side effects of mycophenolate mofetil?
bone marrow suppression, nausea, vomiting, diarrhea, increased incidence of infections
-GI side effects more common when drug is given as sodium enteric-coated tablet
MOA of tetracycline/niacinamide for immune-mediated or inflammatory disease treatment?
properties of tetracycline?
-suppression of in vitro lymphocyte blastogenic transformation and antibody formation
-inhibits matrix metalloproteinases**
-inhibits prostaglandin synthesis
properties of Niacinamide?
-block antigen IgE-induced histamine release in vivo and in vitro
-prevents mast cell degranulation
-photoprotectants from inducing immunologic damage
-cytoprotectant that blocks inflammatory cell activation and apoptosis
-decreases protease release
-ALSO AVAILABLE TOPICALLY
which has a longer half-life: doxycycline or tetracycline?
doxycycline - can use lower dose and longer interval between doses (tetracycline TID)
what does "panepidermal pustular pemphigus" refer to?
cases that have acantholysios, neutrophilic and eosinophilic infiltrate throughout the epidermis (i.e. PVeg and PEryth)
What are primary targets in PF?
Desmocollin 1 and Desmoglein 1
what are primary targets in PV?
Desmoglein 3 (deeper, mucosal involvement)
what are the primary targets in paraneoplastic pemphigus?
plakin famaily antigens: envoplakin and periplakin
what subclasses of immunoglobulin deposits are seen in pemphigus?
IgG2 and IgG4
-intraepidermal Ig deposits are not specific for pemphigus and may be found in 20% of other dermatoses
indirect immunofluorescence is most reliable on which types of tissue for PF and PV?
PF: neonatal mouse skin
PV: canine gingival mucosa
What are three possible immunopathogenic pathways proposed for mechanism by which autoantigens exert their effects?
1) antibodies act by steric hindrance
2) antibody binding triggers intracellular signaling events leading to aberrant phosphorylation of Dsg3 and depleted desmosome formation. protein kinases are modulated by protein kinase inhibitors here.
3) intercellular cohesion is dependent on cholinergic mechanisms with Acetylcholine receptor playing a role in controlling phosphorylation of adhesion molecules:
--atropine and muscarinic Ach antagonists decrease Dsg phosphorylation --> abnormal desmosome formation
T/F: urokinase plasminogen activator (uPA) plays a pivotal role in acantholysis.
what are some drugs that have been involved with drug-induced pemphigus?
PF: cimetidine, itraconazole or Lime sulfur, amitraz/metaflumizone (Promeris) - promeris may have triggered it vs induced
What breeds are overrepresented in cases of PF?
akitas, chow chows
also: cockers, dachshunds, labrador retrievers, english bulldogs
What is the inciting cause of PF?
usually idiopathic, but possible drug-induced or drug-triggered, a subset may develop subsequent to chronic skin disease (allergies), possibly UV light can exacerbate?
which body sites are predisposed to PF lesions?
head, face, ears - often bilaterally symmetric
nasal depigmentation later in disease
which disease shows nasal depigmentation 1st: DLE or PF?
DLE; usually a later event in PF
What is the target antigen for Acquired junctional epidermolysis bulls (AJEB)?
Target antigen: laminin 332
histo: may be acellular
Features: ears, oral cavity, pads, nasal or perinasal
Collagen IV location: 100% bottom of blisters
Salt split IF deposition: both or bottom
What is the target antigen for Bullous Pemphigoid (BP)?
Target antigen: Collagen XVII
Histo: eosinophils intact or degranulated; sub epidermal cleft and vesicle formation
Features: haired skin usually affected, occasional mucosal lesions likely - SPARES PAW PADS
Collagen IV location: both
Salt split IF deposition: top
IgG and IgM are most commonly detected, with some C3
What is the target antigen for Bullous Systemic Lupus Erythematosus type I (BSLE-I)
Target antigen: Collagen VII
Histo: Neutros and histiocytes
Collagen IV location: suspected like EBA (mostly above)
Salt split deposition: bottom
What is the target antigen for Epidermolysis Bullosa acquisitor (EBA)?
Target antigen: Collagen VII
Histo: neutrophils +/- Eos, sub epidermal micro abscesses
Features: concave pinnae, oral cavity, pads and friction sites, multifocal-generalized
Collagen IV location: 43% above, 29% below, 29% both
Salt split deposition: bottom
What is the target antigen for Linear IgA Disease?
Target antigen: Shed collagen XVII
Histo: mild to no inflammation
Features: one case report only
Collagen IV location: below
Salt split deposition: top
What is the target antigen for Mixed AISBD?
Target antigen: Laminin 332 and collagen VII
Histo: cellular vesicles, dermal neuts and eos
Features: affects haired skin and mucosal sites, 2/3 erythematous base to vesicles
Collagen IV location: 100% below
Salt split deposition: bottom
What is the target antigen for Mucus membrane pemphigoid (MMP)?
Target antigen: BPAG 1 (BP230), Collagen XVII, laminin 332
Histo: acellular or. neuts/eos, beta-lichenoid
Features: mostly mucosal or MC Jxn; haired skin sparsely affected, spares pads
Collagen IV location: 91% below, 9% both
Salt split deposition: top more but some bottom or both
Describe Salt-split indirect immunofluorescence testing:
used in indirect immunofluorescence testing with patient's serum.
a 1-molar NaCl solution splits canine lip or gingival skin through lamina Lucida, allowing recognition of autoantibodies that bind to the top (epidermal side of lamina lucida) or bottom (dermal and lamina dense side) or both
what are the autoantibodies in bullous pemphigoid?
Mainly IgG, with subtypes G1 and G4 predominating, but low titers of IgM and IgE have also been detected
Canine and feline cases of BP exhibit antibodies against multiple epitopes of the NC16A collagen XVII molecule
What is another term for BPAG-1?
What is another term for BPAG-2?
BP180 aka Collagen XVII
180 kDa hemidesmosomal transmembranous molecule, target of BP in animals.
What AISBD targets the NC16A domain of collagen XVII molecule?
What is the proposed pathomechanism of blister formation in BP?
(1) binding of complement-fixing pemphigoid anti- body to the noncollagenous domain NC16A of collagen XVII
(2) complement fixation and activation
(3) activation of mast cells and release of chemotactic cytokines, which may be partly mediated or facilitated better by IgE autoantibodies
(4) che- moattraction of neutrophils and eosinophils
(5) release of proteolytic enzymes from the infiltrating leukocytes, which disrupt dermo-epidermal cohesion, resulting in dermo- epidermal separation and vesicle formation
Which proteins were elevated in human blister fluid, suggesting that the release of these from activated granulocytes are important in blister formation?
eosinophil cationic protein, major basic protein, and neutrophil-derived myeloperoxidase and elastase
Which drugs may provoke development of bullous pemphigoid?
sulfonamides, penicillins, and furosemide, UV light
target antigen for BP?
T/f: footpads are generally affected with BP
false, lesions mainly affect skin, oral cavity, LC junctions
T/F: footpads are generally affected with EBA
Compare the main cell types seen histologically for BP, MMP, EBA
MMP: noninflammatory blisters
EBA: neutrophil-rich vesicles
Which AISBD is most common in dogs?
Primary target of MMP?
NC16A domain of collagen XVII; most dogs react to BPAG-2 and many reacting to BPAG-1
Which breeds are overrepresented with BP?
GSD; mature dogs
Clinical signs of Bullous Pemphigoid?
erythema, tense vesicles, hypo pigmentation, erosions/ulcers, SCARRING PREDOMINANTLY
What is the primary target of EBA?
NC1 domain of collagen VII, an adhesion molecule and main component of anchoring fibrils
What is Collagen VII?
An adhesion molecule and main component of anchoring fibrils.
What contributes to blister formation in EBA (and also likely BP)?
granulocyte-derived nicotinamide adenine dinucleotide phosphate (NADPH), oxidase
What breed is overrepresented in cases of EBA?
Great Dane - young dogs
EBA affects paw pads: t/f?
T: over 75% of cases have pads sloughing or ulcerated
EBA affects oral cavity: t/f?
T - oral cavity is always involved
rapid progression to generalized
EBA does not exhibit systemic signs: t/f?
F: pyrexia, depression, lethargy are often present and anemia and thrombocytopenia may be seen
Which AISBD vesicle is acellular?
EBA; can also see neutrophilic microabcesses
AJEB also had reports of acellular vesicles
Which immunoglobulin is most common in EBA?
What treatment options are recommended for EBA?
colchicine, glucocorticoids, IVIg
What kind of autoantibodies do patients with Acquired junctional epidermolysis bulls have?
IgG autoantibodies to laminin 332
What are other names for Laminin 332?
laminin 5, epiligrin, kalinin
What are the targets of Linear IgA disease? and what times of autoantibodies do these patients have in addition to IgA?
IgA and sometimes IgG autoantibodies against processed extracellular components of collagen XVII (including LAD-1 protein)
What are the three troikas of lupus?
The 3 troikas idea is comparing the pathogenesis of Lupus to a traditional Russian 3-horse carriage, where each horse pulls independently but each contributes to the final outcome.
a. Genetic factors
b. Hormonal factors
c. Environmental factors
a. T-cell dysfunction
b. Polyclonal B-cell activation
a. Immune-complex mediated damage
b. Direct damaging effects by autoantibodies
c. Functional effects of antibodies
What dog breed has a predisposition for SLE?
What are signs of SLE-like disease in Nova Scotia Duck Tollers?
Polyarthritis and meningitis/arteritis
Frequently positive ANA titers.
This is a highly inbred breed that can have an MHC II polymorphism. Five loci on chromosomes 3, 8, 11, 24 and 32 were strongly associated with the disease.
What MHC haplotype is associated with SLE in dogs?
MHC I haplotype DLA-A7
environmental factors for SLE?
Can induce or exacerbate symptoms!
hydralazine, isoniazid, phenytoin, procainamide, chlorpromazine in people
Epstein-barr virus in people
hormonal factors for SLE?
More of a big deal for people. Woman are more affected than men (6:1 to 15:1) and especially at higher estrogen periods of their lives. Symptoms can abate around menopause.
Increased estrogen, decreased androgens are risk factors for SLE in people.
Controversial if any sex bias exists for SLE in the dog (2 studies have actually identifed more males) but a lot of pet dogs are neutered so this is more difficult to determine.
No sex predilection reported for the horse.
genetic factors for lupus?
Really complex and multifactorial.
GSD breed disposition for SLE
Association with the DLA-A7 MHC I haplotype in the dog
Nova Scotia duck trolling retrievers that develop an SLE-like disease also have a MHC class 11 polymorphism.
Antibodies against ___ have been reported in cases of VCLE.
Ro/SSA and/or La/SSB in sera from 55% of cases
VCLE has similarities to ___ form of lupus in humans?
What are antibody targets seen in alopecia areata?
bulbar and inferior part of hair follicle with TRICHOHYALIN as major antigen in dogs
-also hair bulb melanocytes?
CD8+ cells are responsible for inducing hair loss in humans. t/f?
T; more CD8+ cells found within hair bulbs in dogs and humans
CD1+ dendritic APCs present in perifollicular dermis
What observations have been seen in humans to support an immunologic basis in Alopecia Areata?
-autoimmune thyroid disease
-increased incidence of autoantibodies
-decreased numbers of circulating T cells
-abnormal presence of Langerhans cells in follicular bulb
-increased MHC class I and MHC Class II expression
-C3 or IgG and IgM deposition at BMZ
-Therapeutic benefit with altering cytokines similar to what's seen by inducing delayed type hypersensitivity
-response to immunosuppressive tx
Breeds predisposed to developing alopecia areata?
GSD, dachshund, beagles
What sites aside from the head and trunk can be affected by alopecia areata?
claws (trachyonychia = roughening, ridging, vertical striations); also see leukotrichia and melanoderma
can be confined to dark-haired areas
Describe trichographic and histopathologic findings of alopecia areata
"exclamation point" hairs, normal telogen, dysplastic hairs
histo: peribulbar to inferior hair follicle accumulation of lymphocytes, macrophages, or dendritic cells with some plasma cells (swarm of bees)
-peribulbar mucin, pigment incontinence
-follicular dysplasia, atrophy in later lesions
in humans, diphenylcyclopropenone (DPCP) is used to treat which disease?
What breed is overrepresented in linear IgA pustular dermatosis?
You have an adult dachshund with multifocal pustular dermatitis on trunk, minimal pruritus. what are your ddx?
linear IgA pustular dermatosis, dermatophyte, folliculitis, demodicosis, PF
What is the half life of IgG?
IgG half life is 23 days (longest)
What is the half life of IgE?
2-3 days (shortest)
Whats the classic histo for lupus?
lymphocyte-rich INTERFACE dermatitis with basal keratinocyte damage (hydropic degeneration)
What lupoid diseases are GSDs predisposed to developing?
DLE, SLE, MCLE...NOT Generalized DLE
What are the subtypes of cutaneous lupus erythematosus?
Discoid LE (--facial/classic, generalized DLE)
What are antinuclear antibodies?
autoantibodies against nuclear components, including DS and Sorry - can't reply yet - message you back in a few? DNA, and histones.
high titers of ANAs seen with human SLE patients so rule out SLE in dogs with ANA titers (also lack of systemic signs supports that there is no SLE).
What Direct immunofluorescence findings are expected with GDLE?
linear deposition of IgG and IgM antibodies at the DEJ
DIF shows continuous and linear IgG deposition along the epidermal BMZ. What is this called?
Positive lupus band test
IgG-positive plasma cells (fluorescent round cells in superficial dermis) are a common finding at what location?
What are common presenting complaints of MCLE dogs?
(50% GSDs) with pain while defecating (Dyschezia) or urinating (dysuria).
well-demarcated multifocal to patchy erythematous erosions and ulcers, symmetrically, with some secondary crusting, especially around perigenital regions...rarely affects lips
Ddx for MCLE
mucocutaneous pyoderma (resolves with antibiotics), MMP (usually affecting GSDs but symmetric erosions and ulcers involving several mucosae and MCJs - but histo of MMP shows microscopic sub epidermal clefts without interface dermatitis)
characteristic histo for MCLE
cell-rich lymphocytic interface dermatitis with basal keratinocyte damage
Interface dermatitis commonly extends to the infundibula of hair follicles.
-potent topical glucocorticoids
-immunosuppressive doses of PO glucocorticoids
- oral CsA (best long-term treatment outcome in GDLE) with steroids at the start
-sun avoidance (SPF >50)
-Hydroxychloroquine, retinoid acitretin led to complete resolution in 50%