Immuno Exam 3 - Lec 30 Type IV

What type of hypersensitivity is delayed?

Type IV

What types of hypersensitivity are antibody mediated?

Type I, II and III

What types of hypersensitivity are T cell mediated?

Type IV

What does delayed hypersensitivity reactions result from?

Interactions among the:
- antigen
- antigen-presenting cells
- T cells
- Macrophages

Are antibodies important in Type IV Hypersensitivity reactions?

No

Why are Type IV Hypersensitivity reactions called delayed hypersensitivity?

Due to delayed appearance of response and symptoms

What is a mechanism established for in Type IV Hypersensitivity reactions?

Elimination of intracellular pathogens

In Type IV Hypersensitivity reactions - what happens if the antigen is not eliminated?

Tissue destruction and granuloma (nodule) formation occurs

What is the clinical presentation of Type IV hypersensitivity reactions?

- Induration: hard, raised lesions
- Erythema and vesicles: reddened skin and fluid filled vesicles

What is the following a clinical example of: Tuberculin reaction (specifically to Mycobacterium spp. Tuberculosis)?

Type IV Hypersensitivity Reaction

What is the following a clinical example of: Contact dermatitis (poison ivy, nickel, chromate, flea collars, dips, sprays, wool, etc.)?

Type IV Hypersensitivity Reaction

What is the following a clinical example of: Stevens Johnson Syndrome (drug coats cell and CD8+ destruction occurs)?

Type IV Hypersensitivity Reaction

When Tuberculin is injected intradermally it is taken up by what cells?

What follows?

- Langerhans cells

- Migration to the draining lymph node

Once cells migrate to the draining lymph nodes what occurs?

They present antigen to memory T cells that respond by generating Th1 effector cells
(*The Th1 cells recognize the antigen when they encounter it)

What is used to identify those suffering from TB?

Mycobacterial extract

What is a crude antigen mixture involved with the Tuberculin reaction?

Purified Protein Derivative (PPD)

What is the major component of PPD?

Probably HSP 65

T or F: There is a delayed hypersensitivity response in animals infected with mycobacteria.

True

What bacteria is associated with TB in humans?

Mycobacterium tuberculosis

What bacteria is associated with TB in bovine?

Mycobacterium bovis (zoonotic TB)

What bacteria is associated with TB in dogs?

Mycobacterium canis

What clinical signs are associated with a Tuberculin Reaction?

Red, indurated (hard) swelling at the injection site

When do clinical signs associated with a Tuberculin Reaction start?

When do they reach its greatest intensity?

- After 12-24 hours

- By 24-72 hours

What happens in very severe Tuberculin Reactions?

Tissue destruction and necrosis may occur at the injection site

What are the lesions associated with a Tuberculin Reaction infiltrated with?

Mononuclear cells (lymphocytes, macrophages) - although neutrophils are present in the first hours of reaction

What are the clinical signs of a Tuberculin Reaction in humans?

- Bad cough of 3 weeks
- Pain in the chest
- Coughing up blood
- Weakness
- Losing weight
- No appetite
- Chills and fever
- Sweating at night

Mycobacterium bovis is associated with what?

Bovine Tuberculosis

Where is Bovine Tuberculosis endemic?

In developing and under-developed cattle-rearing countries (Africa, Asia, Middle East)

Who has ongoing eradication programs for Bovine Tuberculosis?

UK, USA, NZ, Japan, Mexico

What countries are considered TB Free in regards to Bovine Tuberculosis?

Canada, Australia, Iceland, Denmark, Sweden, Norway, Finland, Austria, Switzerland, Luxembourg, Latvia, Slovakia, Lithuanian, Estonia, Czech Republic, Singapore, Jamaica, Barbados and Israel

What does it mean when Bovine Tuberculosis is considered the Zoonotic TB?

Transmitted to people and other animals (deer, goats, pigs, camels, dogs, cats) by inhalation of aerosols or ingestion of unpasteurized milk

What Tuberculin tests are used in cattle?

- Single Intradermal (SID)
- Comparative
- Short Thermal
- Stormont

When is the Single Intradermal Tuberculin test used?

In routine testing

When is the Comparative Tuberculin test used?

When Avian TB or Johne's disease is prevalent

When is the Short thermal Tuberculin test used?

In postpartum animals and in infected animals

When is the Stormont Tuberculin test used?

In postpartum animals and in advanced cases

What are the advantages to using the Single Intradermal Tuberculin test?

Simple

What are the disadvantages to using the Single Intradermal Tuberculin test?

- Prone to false positives
- Poor sensitivity

What are the advantages to using the Comparative Tuberculin test?

More specific than SID

What are the disadvantages to using the Comparative Tuberculin test?

More complex than SID

What are the advantages to using the Short thermal Tuberculin test?

High efficiency

What are the disadvantages to using the Short thermal Tuberculin test?

- Time-consumin
- Risk of anaphylaxis

What are the advantages to using the Stormont Tuberculin test?

Very sensitive and accurate

What are the disadvantages to using the Stormon Tuberculin test?

- 3 visits required
- May sensitize an animal

What other skin tests are similar to a Tuberculin test and what are they used for?

- Brucellin or brucellergen for brucellosis: Extracts of Brucella abortus

- Mallein for Glanders: Culture filtrate of Burkholderia mallei

- Histioplasmin for histoplasmosis

- Coccidioidin for Coccidiomycosis

- Toxoplasmin for toxoplasmosis

When does Allergic Contact Dermatitis appear?

Within 48 to 72 hours

What triggers a reaction in Allergic Contact Dermatitis?

How?

- Reactive chemical on skin

- By binding to PRRs (pathogen recognition receptors) such as TLR4

When considering Allergic contact Dermatitis - when binding to skin proteins (keratin) they act as what?

Hapten carriers

In Allergic contact Dermatitis - what is recognized by skin macrophages?

Langerhans cells

In Allergic contact Dermatitis - where is the antigen presented to T cells?

Lymph node

In Allergic contact Dermatitis - What do activated T-cells produce?

What do they activate?

- IFN-γ and IL17

- Cytotoxic T cells

In Allergic contact Dermatitis - eventually after 24 hours to activate what happens?

What will you see?

- They kill altered cells

- Vesicles, Itches, Sloughing of skin

In Allergic contact Dermatitis - what happens if a re-exposure occurs?

Generates a stronger reaction

What are sources of contact allergens in animals?

- Insecticides in flea collars, sprays and dips
- Wood preservatives
- Floor waxes
- Carpet dyes
- Some pollens
- Creams, ointments
- Leather products
- Paints
- House plants
- Metals- nickel, etc.

What type of hypersensitivity is associated with Atopic Dermatitis?

Type I Hypersensitivity

What type of hypersensitivity is associated with Allergic Contact Dermatitis?

Type IV Hypersensitivity

What are clinical signs of Atopic Dermatitis?

- Hyperemia
- Urticaria
- Pruritis

What are clinical signs of Allergic Contact Dermatitis?

- Hyperemia
- Vesiculation
- Alopecia
- Erythema

Where is Atopic Dermatitis distributed?

- Face
- Nose
- Eyes
- Feet
- Perineum

Where is Allergic Contact Dermatitis distributed?

- Hairless areas
- Usually ventral abdomen and feet

What major allergens are associated with Atopic Dermatitis?

- Foods and pollens
- Fleas
- Inhaled allergens

What major allergens are associated with Allergic Contact Dermatitis?

- Reactive chemicals
- Dyes in contact with skin

How is atopic dermatitis diagnosed?

- Intradermal testing
- Immediate response

How is allergic contact dermatitis diagnosed?

Delayed response on patch testing

What is seen on pathology with atopic dermatitis?

- Mast cell and eosinophilic infiltration
- Edema

What is seen on pathology with allergic contact dermatitis?

- Mononuclear cell infiltration
- Vesiculation

How is Atopic Dermatitis treated?

- Steroids
- Antihistamines
- Hyposensitization

How is Allergic Contact Dermatitis treated?

Steroids

What type of reaction is Stevens-Johnson Syndrome?

Mucocutaneous

What is associated with the following: T cell-mediated hypersensitivity to drugs (around 14 days after drug exposure) - antibiotics - especially sulfa drugs, NSAIDS?

Stevens-Johnson Syndrome

What do people and animals affected with Stevens-Johnson Syndrome develop?

- Rash that blisters into vesicles
- Shed large areas of epidermis and develop skin ulcers (skin, lips, mouth, eyes and genitals)

What are skin ulcers associated with Stevens-Johnson Syndrome due to?

Keratinocyte apoptosis

What is Keratinocyte apoptosis associated with Stevens-Johnson Syndrome due to?

What does this lead to?

- Drugs or their metabolites binding to the epidermal cells and triggering CD95L expression

- Triggering of destruction by CTLs and through apoptosis

What clinical signs are seen with Stevens-Johnson Syndrome in dogs?

- Dyspnea
- Fever
- Vomiting
- Weight loss
- Sloughing of the skin over the nasal planum, footpads, and the oral, nasal, pharyngeal, conjunctival and preputial mucosa

What goes beyond antibody titers?

Diagnostic Immunology

What is used for the measurement of Cell-Mediated Immunity?

In Vitro Assays

What is used as an alternative to a TB skin test?

Measuring cytokine release

What measures the frequency of cytokine-producing cells and is used to quantitate active T-cells?

ELISpot assay

The measurement of T-cell proliferation is achieved by detecting what?

What are cells stimulated to do?

- The uptake of tritiated thymidine

- Divide by specific antigen or a mitogen - the thymidine is incorporated into the DNA of the dividing cells

When measuring T-cell proliferation - When are blood lymphocytes mixed with the antigen?

48 hours

When measuring T-cell proliferation - when do you add the radioactive isotope?

12 hours

When measuring T-cell proliferation - if T-cells are proliferating in response to antigen, the isotope is taken up to make what?

DNA

When measuring T-cell proliferation - what does this provide?

An estimate of the animals reactivity to antigen

When measuring T cell-mediated Cytotoxicity - assume that living cells take up and retain chromium ions - what happens when the cells die?

Chromium is released

When measuring T cell-mediated Cytotoxicity - what are cells incubated with?

Radioactive Chromium-51

When measuring T cell-mediated Cytotoxicity - what is mixed in from an immune animal?

When?

- Lymphocytes

- 24 hours

When measuring T cell-mediated Cytotoxicity - you centrifuge cell debris and measure the solution for what?

Released chromium

When measuring T cell-mediated Cytotoxicity - it is necessary to have a simple method of measuring what?

What is this usually based on?

- Cell death

- The fact that living cells take up and retain chromium ions, but if the cell dies, the chromium is released into the extracellular fluid

When measuring Cytokine Release by T cells - Antigen (tuberculin or purified mycobacterial antigens) is mixed with what?

When?

- Blood lymphocytes

- 24-48 hours

When measuring Cytokine Release by T cells - if cytokine (INFγ) is secreted what can you do with the fluid?

Take it and test

When measuring Cytokine Release by T cells - the ELISA test is specific for what?

IFNγ

When measuring Cytokine Release by T cells - what gives this promise as a diagnostic test?

You're not injecting the animal with the tuberculin antigen therefore not causing a sensitization where an animal (or human) could have an allergic response

A third in vitro assay is the measurement of what?

Cytokine release by T cells

When measuring Cytokine Release by T cells - what is one important example of this?

Measuring the release of IFN- by peripheral blood lymphocytes following exposure to tuberculin or to purified mycobacterial antigens

When using ELISpot Assay - lymphocytes should be incubated on a membrane well that has what?

A capture antibody

When using ELISpot Assay - what happens if cytokine (INFγ), granzyme or perforin is secreted?

Sticks to the well

When using ELISpot Assay - you add a reagent that binds to the product and can see stain where?

On the membrane

What is associated with a capture-antibody directed against the cytokine of interest coating the bottom of plastic tissue culture wells - the cells to be tested are cultured on this surface and expose to the antigen of interest?

ELISpot Assay

What does ELISpot Assay stand for?

Enzyme-Linked ImmunoSpot Assay

To summarize Hypersensitivity Reactions:
I =
II =
III =
IV =

I = Allergy and Anaphylaxis
II = antiBody
III = immune Complex
IV = Delayed