Immunology: Auto immune diseases

Question 1

What are the body’s natural immunosuppressives?

Answer 1

Regulatory T cells (Tregs)
Antibodies (neutralisation / removal of antigen)
Specific cytokines (e.g. IL-10)
Hypothalamus-pituitary-adrenal (HPA) axis important, glucocorticoids eg. cortisol

Question 2

What is broad immunosuppression?

Answer 2

Broad: General effects: many aspects of inflammation and / or the immune response e.g. glucocorticoids and NSAIDs

Question 3

What is specific immunosuppression?

Answer 3

Specific: Targeted e.g. cytokine inhibitors (e.g. Interleukin 1 receptor antagonist (IL-1Ra)
» Binds to the immune protein preventing it from interacting with its receptor.
» Binds to the receptor without activating it, preventing interaction of the immune protein with its receptor (Steric hindrance)
» Inhibiting inflammatory cytokines such as IL-1 and TNF-α are good examples

Question 4

Name a common haem, skin, GI and MSK immune mediated disease?

Answer 4

Haemolymphatic: Immune mediated haemolytic anaemia (common)
Cutaneous: Atopy (VERY COMMON)
GI: Inflammatory bowel disease (common)
MSK: Chronic osteoarthritis

Question 5

How do glucocorticoids work?

Answer 5

Absorbed through cell membrane
Bind to intracytoplasmic receptors, forming complex
Results in:
– reduction of pro-inflammatory proteins and
– increase of anti-inflammatory proteins

Question 6

How do glucocorticoids reduce pro-inflammatory proteins and increase anti-inflammatory proteins?

Answer 6

i) In cytoplasm, a cellular protein binds to the complex –> reduces cells’ response to external inflammatory proteins
ii) Enters nucleus & binds to DNA –> more IkB produced –> protein translation of pro-inflammatory proteins decreases & anti-inflammatory proteins increased

Question 7

In addition to control of inflammatory mediators from the target cells what do glucocorticoids do?

Answer 7

Stablise cell membrane of macrophages, neutrophils & mast cells: This inhibits inflammatory mediators and pro- inflammatory cytokines release (IL-1, IL-6, TNFa)

Inhibit T cell function, and thus B cells indirectly, but direct effects on B cells are less

Inhibit complement function

Down regulate FcRs on phagocytic cells à Igs less effective

Question 8

Cats are more …………. to steroids so ……….

Answer 8

cats are steroid resistant à need higher doses (lower expression of glucocorticoid receptors in cells)

Question 9

What is the duration and potency of cortisone and hydrocortisone?

Answer 9

Short action, low potency

Question 10

What is the duration and potency of (methyl)prednisolone?

Answer 10

intermediate and medium potency

Question 11

What is the duration and potency of dexamethasone?

Answer 11

long (over 48h) and high

Question 12

What should you consider when administering steroids?

Answer 12

Blanket immunosuppression à susceptibility to secondary infections
Mimic endogenous glucocorticoids à chronic use may lead to iatrogenic hyperadrenocorticism
Abrupt withdrawal à adrenal insufficiency, (hypoadrenocorticism)
Withdrawal must be slowly tapered

Question 13

Immune mediated haemolytic anaemia (IMHA) causes binding of antibody to red blood cell membrane which leads to…

Answer 13

Coagulation of RBCs through cross linking of antibodies –> thrombus formation
Recognition of antibody Fc region by Fc receptors on macrophages and neutrophils, leading to phagocytosis of RBCs –> decline in numbers
Recognition of antibody Fc region will activate complement, opsonizing phagocytosis of antibody coated RBCs –> decline in numbers

Question 14

What causes atopic dermatitis?

Answer 14

The allergic reaction occurs when percutaneously absorbed allergens bind to langerhans cells. A series of cellular reactions occurs which results in the production of allergen specific Ig E antibodies. These IgE antibodies are bound to the surface of circulating basophils and mast cells. When they come into contact with allergens, the cells degranulate and release inflammatory mediators e.g. histamine, heparin, proteolytic enzymes. This results in signs of pruritis and erythema

Question 15

What is the treatment of atopic dermatitis?

Answer 15

No money –> no sensitivity testing –> prednisolone

Sensitivity test –> hypoimmunisation

Question 16

Give 6 examples of NSAID’s

Answer 16

Meloxicam
Piroxicam
carprofen
Firocoxib
Asprin/paracetamol

Question 17

How do NSAID’s work?

Answer 17

Most common NSAIDs work by inhibiting cyclo-oxygenase 1 (COX1) and cyclo-oxygenase 2 (COX2).

Question 18

What does COX1 do?

Answer 18

COX1 (constitutively produced) protects intestinal tissues by stimulating mucous production, therefore NSAIDS such as aspirin can cause gastric bleeding and ulceration

Question 19

What does COX2 do?

Answer 19

COX2 is induced during immune responses and is an essential component of the pathway which produces prostaglandins and thromboxanes (Eicosanoids)

Question 20

What is one of the first cytokines produced during inflammation?

Answer 20

IL-1β produced by innate immune cells

Question 21

Name two anti-inflammatory neutraceuticals

Answer 21

Devils Claw: An anti-inflammatory, an analgesic and a digestive stimulant. Its very specific analgesic powers are not too dissimilar in effect from aspirin but without some of the side effects typically associated with it.

Yucca Shidigera Extract: Yucca is one of nature’s best blood purifiers, it is loaded with Vitamin A, B2 and C and is especially beneficial for arthritis and rheumatism. It is also good for the treatment of migraine headaches and internal inflammation

Question 22

How does an ELISA work?

Answer 22

(1) Antigen is immobilized on a solid support either non-specifically (via adsorption to the surface – indirect ELISA) or specifically (via capture by another antibody specific to the same antigen – sandwich ELSIA) (sorbent)
(2) Antigen is recognised by specific antibody (‘immuno’).
(3) This antibody is recognised by second antibody (‘immuno’) which has enzyme attached (‘enzyme-linked’).
(4) Substrate reacts with enzyme to produce product, usually coloured.

Question 23

What are ELISA’s used for in veterinary medicine?

Answer 23

Disease detection e.g. Canine Distemper virus, Canine & feline heartworms, feline leukemia virus, BSE

Detection of illegal drugs in horses, ie Alfentanil, an narcotic analgesic often administered to race horses, or Salbutamol, a bronchodilator.

Detection of hormones, e.g. pregnancy testing kits.

Question 24

What is an indirect ELISA used for?

Answer 24

To measure antibody concentrations in whole blood or plasma or serum

Question 25

What is CRP?

Answer 25

C-Reactive Protein (CRP) – a marker of inflammation

Useful in detecting the severity of post op or immune diseases

Question 26

What is seroconversion?

Answer 26

Development of detectable specific antibodies to microorganisms in the blood serum as a results of exposure, infection of immunization.

Question 27

Why should you always take more than one sample for seroconversion testing?

Answer 27

With a single sample it is not possible to determine when exposure occurred or if it was associated with clinical disease as there is not enough time for the animal to make antibodies. Significant increases in paired samples suggest recent infection.

Paired serum samples (samples that are taken from the same animal), taken at least 10-14 days apart (for some diseases longer time intervals are specified) can be used to assess seroconversion

Question 28

What is the purpose of Direct Antiglobulin test (Coombs Test)?

Answer 28

To identify the presence of non-agglutinating antibodies on the surface of particles such as bacteria or erythrocytes

Question 29

Where is Direct Antiglobulin test (Coombs Test) particularly useful?

Answer 29

1. Neonatal Isoerythrolysis in Horse and Mule Foals
   - The mare produces antibodies against the foal’s red blood cells and transfers those antibodies to the foal through colostrum during the early stages of lactation and nursing. – Coombs test will confirm antibodies attached to foal’s RBC
2. Immune mediated Haemolytic Anaemia (dogs & cats)
   The RBC’s are covered in antibodies so when antiglobulin is added agglutination occurs

Question 30

What is radial immunodiffusion?

Answer 30

1. Antigen solution diffuses into agar with specific antiserum
2. Ring of precipitation forms around antigen well
3. Area of ring is proportional to amount of antigen in the well

Question 31

What are fluorescent dyes used for in immunotesting?

Answer 31

FITC (fluorescin isothiocyanate)
can be chemically linked to antibodies without affecting their reactivity

require stimulation by specific wave length

fluorescence visible under fluorescent microscope (FITC – green)

Question 32

What is a Direct fluorescent antibody test?

Answer 32

To identify the presence of antigen in a cell or tissue sample – direct binding

Question 33

What is Indirect fluorescent antibody test?

Answer 33

To identify the presence of either antigen in a cell or tissue sample or antibody in serum – indirect binding

Question 34

How does a Anti-nuclear antibody (ANA) test work?

Answer 34

1. Cultured cells or frozen sections on a microscope slide are used as source of antigen
2. Dilutions of patient’s serum are applied
3. Incubation with fluorescin labelled antibodies specific to patient’ species antibodies [ie dog]
4. Microscopic analysis (Fluorescent microscope)
   If patient produces nuclear antibodies, than the nuclei will be fluorescent

Question 35

What is the test used for quantitative test of colostrum IgG concentration?

Answer 35

radial immunodiffusion assay