Chapter 8 - Immune system and allergy Flashcards
What is the name for the group of cytokines that have a sole or major purpose to direct of the movement of cells involved in inflammation and the immune response?
Chemokines
Which cells express CD4?
MHC class II restricted T-helper cells
Which cells express CD8?
MHC class I restricted T-suppressor/cytotoxic cells
Which cells express CD3?
Mature T cells
Which cells express CD21?
Mature B cells
Which cells express CD79a?
All stages of B cell development and persists into the plasma cell stage
Which cells express CD90 (Thy-1)?
Dermal dendritic cells
Which immunologically important cytokine is stored by keratinocytes and released following cell damage?
IL-1
What is a unique feature of CD1 antigen presentation e.g. on Langerhans and dermal dendritic cells?
The ability to present non-peptide antigens to T-lymphocytes
Which cell adhesion molecule do Langerhans cells express that dermal dendritic cells do not?
E-cadherin - important for selective adhesion to keratinocytes
Which cytokines are particularly important for B-lymphocytes to differentiate into IgE-producing plasma cells?
IL-4 and IL-13
Match the below Th cells with the cytokines they produce:
Th1 cells
Th2 cells
IL-2, IFN-gamma, TNF-alpha
IL-4, IL-5, IL-10
Th1 cells produce IL-2, IFN-gamma, TNF-alpha
Th2 cells produce IL-4, IL-5, IL-10
Which histamine receptors mediate the anti-inflammatory action of histamine (inhibition of the release of inflammatory mediator substances from mast cells and other WBCs)?
H2 receptors
H1 receptors mediate the proinflammatory response
Which chemokines are considered most potent and selective for eosinophil chemotaxis?
Eotaxin
RANTES
Monocyte chemoattractant protein (MCP) 3 and 4
Arachidonic acid is metabolised into eicosanoids by which enzymes?
cyclooxygenases (COX)
Lipoxygenase (LOX)
Urticaria and angioedema result from degranulation of mast cells and which other cell?
Basophils (mast cell = major effector cell)
How can you differentiate gyrate urticaria from erythema multiforme?
EM does not pit on digital pressure and urticaria does
Name two breeds of horse that are at risk of developing atopic dermatitis?
Thoroughbreds
Arabians
What environmental factor predisposes horses to allergic contact reactions and why?
Moisture (e.g. sweating)
It decreases the effectiveness of the skin barrier and increases contact between the agent and the skin surface
Which type of Ig binds antigens and aids removal of them from intestinal mucus?
IgA
At what age do horses typically develop IBH?
3-4 years
Which pigmentary changes can be seen with IBH?
Melonoderma and melanotrichia
When present, which pattern of urticaria is seen with IBH?
Papular urticaria
Are mosquito nets effective in reducing Culicoides exposure?
No, they can still pass through the mesh - need ultrafine mesh screens/netting (60 squares per square inch)
Is IL-31 mRNA expression increased in lesional skin in Culicoides hypersensitivity?
Yes
In IBH, there is an IgE-mediated, type I hypersensitivity reaction to Culicoides allergens with activation of mast cells, followed by a late-phase reaction characterised by infiltration of which cells?
Lymphocytes and eosinophils
Is eosinophilia associated with severity in IBH?
Yes
In response to ASIT, IgG antibodies are produced, in particular ____ that block the binding of allergen-specific IgE antibodies to the allergens.
IgG4
ASIT is associated with decreased production of ___ and ___, the signature cytokines of Th2 CD4+ T cells, and an increase of the allergen-specific Treg with the production of regulatory cytokines, ____ and _____.
IL-4 and IL-5
IL-10 and TGF-β
Allergens from which Culicoides species have been identified and produced?
C. nubeculosus
C. sonorensis
C. obsoletus
Prophylactic use of intralymphatic injections in Icelandic horses with small amounts of recombinant allergens in Alum and monophosphoryl lipid A (MPLA, aTLR-4 agonist) resulted in what response?
Th1/Treg immune response (IFN-γand IL-10) with induction of high specific IgG (IgG1 and IgG4/7) antibodies levels, displaying a strong blocking capacity
In horses with IBH, linkage of equine IL-5 to virus-like particles of the cucumber mosaic virus (CuMV) generated polyclonal antibody responses against IL-5. What is the role of the virus-like particles?
- Small size (20–200 nm) enables free draining into the lymphatic systems and binding to B cell receptors
- Their surface is highly repetitive allowing B cell receptor cross-linking inducing potent antibody responses in absence of T cells
- Complement fixation via complement receptor 2 and subsequent follicular dendritic cell activation driving T cell–dependent differentiation of germinal center B cells into class-switched affinity-matured long-lived plasma cells
- Contain non-coding E.coli RNA activating innate immune receptors for pathogen-associated molecular patterns (PAMPs) such as toll-like receptor (TLR)-7
In horses with IBH, are the vaccine-induced anti-IL-5 antibody titres reversible?
Yes - important safety mechanism
A vaccine targeting which other cytokine has been studied for use in horses with IBH?
IL-31
In the study by Huhmann and Mueller (2019), topical application of PUFAs (1% concentrated fish oil [EPA, DHA], humectants and emollients – KERECIS Smooth) was used on half the body of horses with Culicoides sensitivity. What effect did it have on pruritus?
No significant effect
In the study by Huhmann and Mueller (2019), topical application of PUFAs (1% concentrated fish oil [EPA, DHA], humectants and emollients – KERECIS Smooth) was used on half the body of horses with Culicoides sensitivity. What effect did it have on lesion scores?
Significant improvement over 28 days
In the study by Huhmann and Mueller (2019), topical application of PUFAs (1% concentrated fish oil [EPA, DHA], humectants and emollients – KERECIS Smooth) was used on half the body of horses with Culicoides sensitivity. What adverse effects were seen?
Sun-burn like signs (erythema, scaling, swelling, crusts, alopecia) at sites of application (3/21)
Have ultrastructural abnormalities in lipid lamellae and disorganization of the stratum corneum, as in dogs and people, been reported in horses?
Yes – unclear if result of inflammation or primary impairment
Do horses with atopic dermatitis often develop secondary Staphylococcal infections, as dogs do, that lead to increased pruritus, folliculitis and hair loss?
Yes
Which pruritogenic mediators can stimulate pruritus, other than IL-31?
Histamine, proteases, substance P, opioids, neurotrophins, and other neuroactive peptide
Icelandic horses imported to Culicoides infested areas that do not develop IBH during their first summer of exposure show an increase in which Ig?
IgG5 - may be predictive of developing IBH the following year
Do Icelandic horses imported as foals or bred in Culicoides endemic areas show as high a prevalence as those imported later in life (> 50%)?
No – those born in Europe and USA show similar prevalence to other breeds e.g. 8-10% (Swedish-born Icelandic horses, Shetlands and Belgian Warmbloods)
What is the heritability of IBH?
- 08-0.36
0. 16 (Friesians), 0.24 (Dutch Shetlands) and 0.27 (Swedish-born Icelandic horses)
IBH mainly involves type I hypersensitivity - what are the key events in type I hypersensitivity sensitisation phase?
- IL-25, IL-33 and TSLP are released from injured epithelial cells inducing type 2 ILCs to produce IL-5 and IL-13
- APCs direct a Th2 response with product of IL-4 and IL-13
- B cells undergo class switching and produce allergen specific IgE that binds to high affinity FcεRI receptors on basophils and mast cells, leading to sensitization
When does the late phase reaction associated with a type I hypersensitivity reaction peak?
24 hours post exposure
True or false; Expression of CD209 (DC-SIGN), FCER1 and CD11C, as well as HRH4, encoding the histamine 4 receptor, shown to correlate with IDECs (inflammatory dendritic epidermal cells) were upregulated in lesional CH skin
True
Are CD4+ or CD8+ cells increased in the skin of horses with IBH?
CD4+
Have levels of IL-4 and IL-13 been shown to be elevated in the skin of horses with IBH?
IL-13 (and IL13RA1 and IL13RA2) are elevated
IL-4 has not been shown to be elevated (may have a more central role)
Are Th2, Th1 and Th22 signatures upregulated in CH?
Yes
Eosinophils infiltrating the skin of CH lesions is part of what stage of hypersensitivity reaction?
Late phase reaction of type I
May also represent at type IVb delayed reaction
TSLP expression in CH is most likely induced by what?
- Mechanical damage of the skin caused by the bites of Culicoides and the cocktail of salivary proteins which they inject while feeding
- The allergic cytokine milieu present in CH lesions and possibly also secondary bacterial infections, also could contribute to TSLP production
Histamine is found in the saliva of Simulium; what is it presumed role?
Vasodilation through action on H1 receptors and further inflammatory reaction via H4 receptors on leukocytes and mast cells
Does Culicoides saliva contain histamine?
Not proven
What role does 5-hydroxytryptamine have in insect bites/stings?
It stimulates sensory nerves eliciting itch and pain – not demonstrated in Culicoides saliva
The major source of histamine and 5-HT in CH is likely to be the mast cell
Name the two IL-31 receptor subunits that are upregulated in lesional CH skin
IL31RA and OSMR
Cvitas et al. (2020) demonstrated downregulation of which group of genes in lesional skin of horses with IBH?
Genes involved in adherens and tight junction formation
Has an imbalance between the Th-2 and regulatory T cell (Treg) response been demonstrated in IBH?
Yes – in allergen-stimulated PBMC as well as locally in the skin
True or false; in the study by Cvitas et al. (2020), genes involved in metabolism of epidermal lipids, pruritus development, as well as IL-25, were significantly differentially expressed between non-lesional CH skin and healthy skin
True - but close to healthy skin and no tests of epidermal barrier function performed
In the study by Thomas et al. (2021), which risk factor was associated with equine asthma?
Obesity
Have SNPs in TSLP been documented in horses with IBH?
Yes
What mechanisms help to prevent absorption of allergens from the GI tract?
- Mucus traps antigens
- Gastric acid/enzymes break down antigens
- Tight junctions block passage between epithelial cells
- IgA binds antigen to be removed by mucus if in the lumen or by the liver
Epithelial cells can produce cytokines such as thymic stromal lymphopoietin (TSLP), IL-25, and IL-33.
These cytokines have the ability to influence ____________ that in turn affect proliferation and differentiation of naïve T cells into Th-2 subtype producing ____, ____ and ____.
Dendritic cells (DCs)
IL-4, IL-5, IL-13 and TNF-α
IL-4, IL-5, IL-13 and TNF-α cause in vivo expansion of _____________ that are an important early source of the type-2-cell-associated cytokines IL-5 and IL-13, and to a lesser extent, IL-4.
Innate lymphoid cells type 2 (ILC2s)
ILC2s themselves are capable of controlling a type 2 innate immune response, but often collaborate with ______ cells in order to develop fully blown type2 immunity
CD4+ Th-2
Which are the main points of IBH treatment?
- Control the itch to prevent additional self-trauma.
- Resolve secondary infections.
- Prevent additional bites.
Name environmental measures to manage IBH
- Strong fans when gnats are most active (dusk and dawn)
- Move horses to paddocks further away from stagnant water
- Protective blankets
- Fly masks and fly sheets (frequent change to avoid secondary infection)
- Daily use of insect repellents (permethrin or synthetic pyrethroids like cypermethrin)
Which topical repellents can be used in IBH?
- Spot-on formulations with 44% to 64% permethrin on specific problem areas (pole, base of the tail, base of the neck) once weekly
- Sprays with lower concentrations (2% permethrin) to cover the rest of the body.
Regardless of the product used, frequent (in most cases daily) reapplication is key, because even the best product does not have a long residual efficacy when horses sweat or are in high-humidity climates.
What type of topical glucocorticoids can be used in IBH? Which one of them is used for localised lesions such as face and ears?
- Topical triamcinolone spray
- Leave-on hydrocortisone conditioner
- Glucocorticoid shampoos and lotions containing (fluocinolone acetonide)
- Lotions are handy for localised lesions where shampoo therapy is not amenable
What systemic glucocorticoids are used in IBH?
Prednisolone (preferred over prednisone)
Dexamethasone (more potent)
Triamcinolone (even more potent, not preferred - laminitis risk)
Is laminitis following glucocorticoids administration often reported? In which horses systemic administration should be used with caution??
The occurrence of iatrogenic laminitis in healthy horses appears to be very low
- In a retrospective study involving horses with various medical conditions (including laminitis), oral prednisolone did not appear to increase the risk of laminitis (prevalence of laminitis 3.7% pred horses- 5.7% healthy horses).
- In horses with previous laminitis history, equine metabolic syndrome, pituitary pars intermedia dysfunction, concurrent gastrointestinal disease.
ASIT for IBH prevention has been tested with which formulations/routes of administration? What were the results?
- Repeated injections of r(recombinant)-Culicoides allergens into submandibular lymph nodes (6 Icelandic horses) and intradermally (6 Icelandic horses)
- Continuous oral application of transgenic barley flour expressing Culicoides allergens using a modified bit.
IgG antibodies produced were shown to partially block binding of some Culicoides allergen-specific IgE from IBH affected horses.
Following second year booster vaccination against IL-5, what percentage of tested IBH horses showed 50% improvement of clinical lesions?
88% of horses reached a 50% improvement (cf 69% in first year) and 57% reached a 75% improvement (cf 31%)
What were the results following vaccination against IL-31?
- Vaccination against eIL-31 reduced clinical scores when compared to previous untreated IBH season of the same horses and to placebo-treated horses in the
same year. - No pruritus evaluation
Equine atopic dermatitis. What drugs are used? Which are used in flare-ups and which in more chronic/maintenance cases?
- Glucocorticoids (systemic/topical, for acute, severe cases)
- Antihistamines (moderate cases, long-term if needed)
- Pentoxyfylline (moderate cases, long-term)
- Essential fatty acids (moderate cases, long term, usually in combination with antihistamines)
When it is most beneficial to use antihistamines? What antihistamines are used in the horse?
Usually before the beginning of the allergy season.
Hydroxyzine, chlorpheniramine, cetirizine
What are the potential side effects of pentoxyfylline?
Sweats and irritability
What are the reported percentages of efficacy of ASIT in equine atopic dermatitis?
56% to 93%
64% to 84% in Marsella (2021)
When do atopic horses on ASIT treatment start to show a response?
Usually after the first 6 months of therapy, some show improvement in the first 2-3 months. It takes a full year to assess the result of ASIT.
What percentage of atopic horses has been successfully been stopped off ASIT and after what duration of treatment?
27%
Mean duration of treatment 2 years
Is SLIT equally efficacious with SCIT in equine atopic dermatitis?
At the moment there are not many validated studies on SLIT but the SC route is considered to be beneficial.
Which adverse effects have been reported with SLIT in horses?
Scholz et al., 2016, VetDerm: Thirty six hours after commencing SLIT, a mare developed scleral oedema, moderate dyspnoea and abdominal discomfort. SLIT was withdrawn for 10 days and re-instituted using a ten-fold dilution of the original vaccine. Localized oedema and swelling of the tongue developed within 12 h of administration.
Which foods are common culprits for equine food allergy?
Hays rich in protein such as alfalfa or peanut
Soybean
What type of hypersensitivity reaction is a contact allergy?
Type 4
Name the identified host and environmental factors that influence the prevalence of IBH
Habitat
Climate
Age
Breed
Genetic predisposition
Coat colour (conflicting results - chestnut/grey may be lower risk?)
Exposure in early life (may be protective)
MHC has been reported to contribute to IBH In which breed of horse?
Friesians
Intradermal injection of Culicoides extracts provokes a skin reaction in what % of IBH affected horses?
80%
True or false; IgE-bearing cells in the skin biopsies of horses with IBH are found at an increased frequency when compared to healthy controls
True
A combination of the top 7 r-allergens could diagnose > 90% of IBH-affected horses with a specificity of what %?
> 95%
True or false; IgG antibodies to Culicoides salivary gland antigens are also detected, not only in the serum from IBH-affected horses but in ALL horses exposed to Culicoides
True
IBH horses have higher numbers of IL-__ cells in their blood compared to normal horses
IL-4+
Healthy horses have increased regulatory cells
True or false; Th1 response is considered protective against IBH
True
Can IBH be associated with equine asthma?
Yes
What are the primary signs of IBH?
Pruritus
Papular eruption
Can also see urticaria and eosinophilic granulomas
What are the reported sites of clinical signs with IBH?
Face, ears, dorsal midline (base of the mane, tail), ventral midline, legs
What concentration of Culicoides antigen is recommended for IDT?
1/1000 w/v concentration
Pruritus and dermatitis on the face and __________ can be associated with seasonal environmental allergies
Flexural surfaces
In the WCVD abstract by Enck et al. (2020), inhibition of IgE against CCD substantially decreased positive
results for which allergens
Pollens only
What does this image of the stratum corneum from a horse with atopic dermatitis show?
Disorganised lipid material in the intercellular space compared to a healthy horse
Has oclacitinib been given to horses?
Yes - effective at 0.25 mg/kg SID
SID as it has a longer half-life in horses
Can IDT differentiate between asthmatic and non-asthmatic horses?
No
Lo Feudo et al. (2021); which were most the common IDT reactions in asthmatic horses?
Insects, Dermatophagoides spp. and dog epithelium
How does allergen stimulate sensitised mast cells?
By crosslinking of IgE and two or more high affinity FcεRI.
This provokes degranulation and release of preformed mediators such as histamine, but also to the de novo synthesis of leukotrienes and several cytokines
Type IV hypersensitivity can be split into four subclasses; which cells are involved in types a, b, c and d?
A) CD4(+) Th1 cells and monocytes/macrophages
B) CD4(+) Th2 cells and eosinophils
C) cytotoxic CD8 (+) T cell-derived perforin and granzyme B-induced necrosis and apoptosis
D) T cell-driven sterile neutrophilic inflammation
Is IL-31 expressed in normal equine skin?
IL-31 was exclusively expressed in lesional skin of CH affected horses, whereas it was absent in non-lesional skin of affected horses or healthy skin of healthy horses
The mechanism of action of ASIT is to induce allergen-specific ____ that compete on allergen binding sites with allergen-specific IgE antibodies.
IgG
It also binds to the inhibitory FcγRIIB receptor on mast cells and basophils preventing degranulation of the latter
What are the major allergens for CH?
Cul o 1P Cul o 2P Cul o 7 Cul o 8 Cul o 9 Cul o 10 Cul o 11
What are the minor allergens for CH?
Cul o 3
Cul o 5
Testing with the seven major recombinant allergens for CH has what sensitivity and specificity?
Combination of these seven r-allergens could diagnose > 90% of IBH horses with a specificity >95%
How reliable is IDT when two tests are performed at the same time on either side of the neck? Van Damme et al. (2020)
Only the IDT results of D. farinae, L. destructor, perennial rye and birch pollen mixture can be reliably assessed at 30 min.
Found high variability in both the IDT and the macELISA and smELISA
What are mac- and smELISAs?
macELISA = monoclonal antibody cocktail-based ELISA smELISA = specific single monoclonal anti-IgE antibody
Cutaneous lupus erythematosus is rarely reported in horses and once in a donkey; which treatment was successful?
Methotrexate
NAVDF abstract Fernandes (2021); are CCD present in healthy and atopic horses?
Yes - horses with anti-CCD IgE exhibited
greater polysensitisation than horses without anti-CCD IgE in all allergen groups except mites - CCD blocking reduced polysensitisation by 43%
The lesional IBH signature exhibits upregulation of itch-signalling, innate and adaptive immune genes with a dominance of IL-__ pathways
IL-13
