Immunology 4 Flashcards
What determines whether glucocorticoids have an immunosuppressive or an anti-inflammatory effect?
Dose administered
Outline some side effects of glucocorticoid use
- Blanket immunosuppression so susceptible to secondary infections
- Mimic endogenous glucocorticoids and so chronic use may lead to iatrogenic hyperadrenocorticisim
- Abrupt withdrawal can lead to Addisonian crisis
Explain how immune mediated haemolytic anaemia (IMHA) may occur
- Lots of mechanisms
- Coagulation: cross-liinking of antibodies, leading to thrombus formation
- Recognition of Ab Fc region by Fc receptors on macrophages/neutrophils => phagocytosis of RBCs
- Recognition of Ab Fc region, activate complement, opsonisation and phagocytosis
- Alloantibpdy rendering RBC susceptible to removal
- Drugs/infection modifying antigen leading to destruction
Describe the treatment of immune mediate haemolytic anaemia with corticosteroids
- Reduce egress of inflammatory cells into tissues
- Reduction in inflammatory mediators
- Suppression of macrophage and neutrophil function
- Lymphocytotoxic
- Reduced macrophage Fc receptor expression
- Inhibition of complement
What is atopic dermatitis/atopy?
Type I hypersensitivity reaction to environmental allergens
Explain how atopic dermatitis occurs
- Occurs when percutaneously absorbed allergens bind to Langerhans cells
- Production of allergen specific IgE antibodies
- Bound to surface of circulating basophils and mast cells
- Degranulate when come into contact with allergens, release inflam mediators e.g. histamine, heparin
- Results in pruritus and erythema
Describe acute atopic dermatitis specifically
- Early stages of immune response
- IgE mediated mast cells phenomenon
- Th2 cytokines involved
- On re-exposure, IgE already produced, binds to allergen, many already bound to mast cells by FcR, release inflam mediators
Describe chronic atopic dermatitis specifically
- Recruitment of multiple cell types
- Immune mediators of Th1
- Leads to irritation
- Secondary infection may occur
Outline the treatment options for atopic dermatitis
- If no sensitivity testing, then prednisolone
- If sensitivity testing, then hypoimmunisation following identification of allergen
- Shampoo to alleviate worst symptoms
- Histamine
Describe the therapeutic treatment of atopic dermatitis
- Systemic/topical corticosteroids
- Cyclosporine (atopica), inhibits T lymphocyte function
- Oclocitaib maleate (apoquel): selective molecule which inhibits Janus kinase 1 (JAK1) signalling pathway (part of itch)
- Monoclonal anti-canine IL-31 antibody (itch cytokine, new method)
What are autologous biological products?
Products prepared from whole blood of individuals and adminstered back to the same individual
What is IL-1beta?
- Pleiotropic cytokine affecting many biological functions
- One of first cytokines produced in inflammation (leads to fever, inappetance)
- Produced by, and stimulates innate immune cells (incl maturation of APCs and production of inflammatory cytokines)
Outline the use of IL-1Ra
Usually horses, osteoarthritis treatment, administered intra-articularly
Explain how IL-1Ra works
- Competitive inhibitor of IL-1beta
- Steric hindrance
- Does not have intracellular signalling capability so no production of effector proteins
Where do NSAIDs exert their action?
On COX-1 and COX-2 in the arachidonic acid metabolism, preventing production of eicosanoids (PGs and thromboxane)
Where do corticosteroids exert their action in arachidonic acid metabolism?
On annexin A1 (phospholipase) (required to release arachidonic acid from phospholipid membrane)
Describe the arachidonic acid (Aa) metabolism
- Aa esterified in membrane phospholipid
- Phospholipase A2 isolates arachidonic acid
- Arachidonic acid produces prostagland G2
- Metabolised by COX1 or COX2 to produce prostaglandin H2
- Tissue specific isomerases produce either prostacyclin, thromboxane, prostaglandin E2 or prostaglandin F2alpha
What is the action of thromboxanes and prostaglandins?
Vasoactive lipids
What is produced if arachidonic acid is metabolised by lipoxygenase pathway?
- Production of leukotrienes
- lead to pain, fever, vascular permeability increase, chemotaxis of PMNs
What is the risk of blocking COX-1?
Can lead to ulceration and bleeding of gastric mucosa, therefore blocking COX2 is preferable
Give examples of natural food supplements that may have anti-inflammatory properties
- Devils claw
- Green lipped mussel
- Glucosamine
- Chondroitin
What is primary immune deficiency?
- Appears early in life
- Rare immune gene mutation
- Genetic/congenital and may be hereditary
What is secondary immune deficiency?
- Occurs in adult which has previously been normal
- Occurs due to secondary factors e.g. age, drugs, chronic disease or infection
Give examples of primary canine immunodeficiencies
- Canine IgA deficiency
- Canine leukocyte adhesion deficiency (CLAD)
- X-linked severe combined immunodeficiency (X-SCID)
Describe the occurence, cause and biological effect of canine IgA deficiency
- Common, Shar Pei, GSD
- Not mutation in gene, functional deficiency in IgA production
- Sub-normal IgA, mild chronic mucosal infections
Describe the occurrence, cause and biological effect of canine leukocyte adhesion deficiency
- Rare, red Irish Setter
- B2 leukocyte integrin CD8 gene mutation
- Blood neutrophils cannot adhere to vascular endothelium enter tissues
- Neutrophilia
- Multiple systemic infections
Describe the occurence, cause and biological effect of X-linked severe combined immunodeficiency (X-SCID)
- Rare, Bassett hound, Cardigan Welsh corgi, Jack Russell terrier, Arabian horse
- Bassett X linked, not X linked in Corgi
- IN JRT mutation in DNA protein kinase gene
- Cytokine receptors mutated, T cell response to antigen inhibited, no immune response
- Viral andbacterial infections post colostral Ab decline
- Lymphopaenia, hypoplastic lymphoid tissue
- IgG and IgA absent
Explain how CLAD leads to loss of expression of beta-2 integrins
- Lack of CD18 expression
- Is a beta-2 subunit, and required to make up this surface receptor
- Cannot bind to CD-11 so beta-2 integrin cannot be formed or function
What are the 6 causes of secondary immunodeficiency?
- Immunosensecence
- Drugs
- Malnutrition
- Stress
- Concurrent disease
- Chronic disease
Describe the effect of FIV on the immune system
- Can cause secondary immunodeficiency
- Enlargement of lymph nodes, are also site of viral proliferation
- Decrease in CD4+ T cells, inverted CD4:CD8 ratio occurs
- Lymphocyte blastogenesis to T and B cells mitogens is impaired
- decrease in production of Th1 cytokines (due to reduced CD4+)
- FIV replicates in lymphocytes
Describe the acute phase of infection with FIV
Mild illness, progressive decline in blood CD4+ T cells
Describe the second phase of FIV infection
- Asymptomatic
- Continued CD4+ T cel decline over many years
- CD4:CD8 ratio declines
Describe clinical disease caused by FIV
- Recurrence of mild illness, progresses to severe terminal stage 4-5 of disease
- Chronic, multi-systemic diseases including gingiovitis, respriatory tract infection, enteritis, dermatitis, weight-loss, pyrexia, lymphadenopathy
- Neurological disease and lymphoma may develop
- Secondary infections may occur