Week 9 Flashcards
(19 cards)
Local tolerance studies
corrosion, irritation, sensitization & phototoxicity tests
In vitro corrosion test examples
Transcutaneous Electrical Resistance (TER) Assay (rodent)
CORROSITEX Test - colour change on biobarrier membrane
Episkin test - topical on human skin culture
In vitro irritancy test examples
Episkin, Epiderm, prediskin, Non-Perfused Pig Ear Test, Mouse Skin Integrity Function Test (SIFT)
In Vivo Irritancy Tests
primary eye, dermal irritation, modifized draize test
Not immune mediated
Modified Draize test procedure
- Usually performed in a rabbit
- Direct application of liquid (0.5 mL) or solid (0.5 g) to shaved back, using patch dressings
- Apply for 4 or 24 hr
- Evaluated at 24, 48 & 72 hr and graded for:
- redness (erythema),
- swelling (oedema),
- scab formation (eschar)
- with a comparison to Solvent/vehicle control
Modified Draize test scores (animal)
Erythema & Eschar Formation
Oedema Formation
Scores from 0-4
Modified Draize test scores (Human)
- To determine irritancy (and hypersensitivity) of substances directly applied by patches (1 to 72 hr) to the skin of volunteers
- Similar scoring for oedema, erythema & eschar (of 0 to 5)
- Evaluation timepoints at 0.5, 1 & 24 hr, 3-4d
- Cumulative irritation assays assessed following 10-21 d of application, with patch being replaced every 24 hr
Sensitisation (allergy) tests
For repeated contact. Performed on guinea pigs. Measures erythema and oedema
3 phase - induction, rest, challenge
Mouse local lymph node assay
Sensitisation test of mouse ear.
- In vivo sensitisation of ear
- After the rest period, the local lymph node is excised and cells are removed
- Cells challenged in vitro with chemical
- Considered more humane as animal does not experience an allergic reaction
immunotoxicity causes
inhibition of immune function OR Inappropriate enhancement of immune function
Immunotoxicity testing
A very sensitive test to immunotoxins: Enumeration of immune cell populations by flow cytometry
Combining a few tests for accurate assessment: Immune cell enumeration + immune function test
In vitro Cytokine Release Assays (CRAs) in human cells
Tier 1 tests
Immunopathology: blood cell counts, organ weights & histology of immune tissue.
Humoral-mediated immunity: B cell mitgenesis toward lipopolysaccharides stimulation, specific antibody concerntrations, number of IgM antibodies plaque-forming cells
Cell-Mediated immunity (Proliferation + Tumoricidal): NK activity, T cell mitogenesis
Tier II tests
Immunopathology: quantitation of splenic immune cells by flow cytometry
Humoral-mediated immunity:, number of IgG antibodies plaque-forming cells
Cell-Mediated immunity: cytotoxic t cell cytolysis, delayed hypersensitivity response.
Host resistance: syngenic tumour cells to test NK, macophages
Macrophage function: phagocytosis of ectoenzymes
Lymphocyte Proliferation Assa
by MTS or 3 H-Thymidine
3 Types of Immune Reponses
- Intracellular (Type 1): intracellular infections, damaged cells
- Mucosal (Type 2) for parasites and defence of mucosal barriers
- Extracellular (Type 3) primarily for bacteria and fungi
Type I: Respiratory hypersensitivity
‘immediate’, anaphylactic allergy; IgE-mediated
APCs interact with TH 2 cells that promote B cells to produce IgE –> binds to Fc receptors on mast cells and basophils.
Crosslinks cause degranulation, vasodilation, bronchoconstriction
Type II hypersensitivity
Antibody-dependent cytotoxic hypersensitivity
(complement-fixing IgM and IgG): med. signif. for transfusion reactions.
Type III hypersensitivity
Immune complex-mediated hypersensitivity
(IgG, IgM, & C-activation): common complication in autoimmunity
Type IV hypersensitivity
Cell mediated hypersensitivity (‘contact’ or delayed-type response)
contact eczema
