Term
| How many hours does it take for a type 4 hypersensitivity reaction to occur? |
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Definition
| 24-72 (delayed type hypersensitivity DTH) |
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Term
| What causes type 4 hypersensitivity? |
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Definition
| Caused by cell-mediated immune response |
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Term
| What happens when CD4 cells are activated? |
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Definition
| Activation of CD4 Th1 cells -> macrophage reruitment and activation -> granulomatous inflammation |
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Term
| What happens when CD8 cells are activated? |
|
Definition
| Activation of CD8 T cells -> lysis of target cells |
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Term
| What causes contact allergy dermatitis? |
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Definition
| Usually caused by small molecule chemicals that penetrate the skin |
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|
Term
| What are some possible sources of chemicals? |
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Definition
| Flea collars, antibiotics, floor waxes, paint and house plants |
|
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Term
| What is the mechanism for contact allergy dermatitis? |
|
Definition
| Binding to MHC ll and MHC l molecules of Langerhans cells -> migrate to draining lymph node -> activate CD8+ and CD4+ T cells -> migrate to the skin -> recruitment of monocytes, apoptosis of keratinocytes |
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Term
| Testing for prior or active infection with Mycobacterium bovis or M. tuberculosis |
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Definition
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Term
| How much purified protein derivative do you inject and where? |
|
Definition
| 50 microliters intradermally (caudal fold or side of neck) |
|
|
Term
| When do you check for swelling after a caudal fold test? |
|
Definition
|
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Term
| What is the pathogenesis for the tuberculin reaction? |
|
Definition
| Uptake of tuberculin by dermal DCs -> migrate to draining LN -> activate Th1 cells -> migrate to skin -> secrete IFN-gamma and chemokines -> recruit and activate macrophages -> granulomatous inflammation |
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Term
| How do you get a false positive in a tuberculin reation? |
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Definition
| Crossreaction with other (non-tuberculous) mycobacteria |
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|
Term
| How do you get a false negative in a tuberculin reaction? |
|
Definition
1. advanced disease
2. early infection
3. very old cows |
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|
Term
| What is an alternative test to a tuberculin reaction that you can do? |
|
Definition
| In vitro stimulation of peripheral blood lymphocytes with mycobacterial antigen -> measure IFN-gamma by ELISA |
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Term
| What causes erythema multiforme and toxic epidermal necrolysis? |
|
Definition
| Caused by type 4 hypersensitivity reactin to drugs, sometimes infections |
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|
Term
| What happens in erythema multiforme and toxic epidermal necrolysis? |
|
Definition
| Killing of keratinocytes by CD8 T cells and NK cells |
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Term
| What do you see with erythema multiforme and what is the prognosis? |
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Definition
| Erythematous macules and plaques on the trunk, foot pads, ears and mucocutaneous junctions, good prognosis and may spontaneously regress |
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Term
| What do you see in toxic epidermal necrolysis and what is the prognosis? |
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Definition
| Erosions and ulcerations of trunk, foot pads and mucocutaneous junctions, poor prognosis-death caused by sepsis and dehydration |
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|
Term
| What is the treatment for toxic epidermal necrolysis? |
|
Definition
| Remove inciting drug, fluid and electrolyte therapy and antibiotics |
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