B&I allergy Flashcards
Name the major types of Type 1 allergies
Asthma, allergic rhinitis (hay fever), dermatitis, eczema, urticaria (hives), insect allergies (bee stings, dust mites), animal dander, drugs (penicillin), food (gluten, peanut), nickel (metal contact dermatitis), anaphylaxis
What are the 4 classifications of hypersensitivity? How long do they take to appear?
Type 1: atopic (immediate)
Type 2: complement mediated (medium)
Type 3: serum sickness (medium)
Type 4: delayed type (slow)
Describe type 1 atopic allergy (2)
- Mast cells protect against complex (large, multicellular) organisms
- Antigen attaches to IgE, mast cells activate and degranulate
What are mast cells? (5)
- Myeloid cells in the skin
- Relate to innate immunity
- Have Fc receptors, which have high affinity to IgE antigen complexes
- IgE can be pre-primed with antigen
- When IgE binds large complex antigens (eg. pollen) it triggers local mast cells to rupture and empty their granules
Describe type 2 hypersensitivity (2)
- Involves Fc, complement and phagocytes (neutrophils)
- Slower reaction compared to type 1
What causes type 1 allergic reactions? (4)
- B-cells (IgM) recruit an allergen
- CD4 (Th1, Th2) helper T cells recruit cytokine which causes IgM to change to IgE
- Results in IgE producing memory cells
- IgE response to allergen sensitises mast cells in skin
What are the physical effects of type 1 allergic reactions? (4)
What is this caused/regulated by?
- Can cause smooth muscle and blood vessels to constrict
- Mucous glands to secrete (swelling)
- Stimulates sensory nerve endings (pain)
- Attracts platelets and other cells
Caused by degranulation, regulated by histamine
What is the role of antihistamines? (2)
- Antihistamines look like histamines
- Blocks the histamine receptor to prevent physical affects of type 1 allergic reaction
What happens in Rhesus (RhD)? (Type 2 hypersensitivity)
4
- An antibody present in newborn baby reacts to protein on RBC
- Neutrophils become frustrated and digest RBD membrane causing lysis and haemolytic anaemia
- Caused by RhD antigen
- Mother RhD - , father RhD + , RhD gets into mothers bloodstream which causes antigens to produce, which travels across placenta and harms baby
Describe desensitisation treatment (2)
- Drop allergen in scratch on skin, inject patient with allergen, slowly increasing dose
- Aims to produce HIGH AFFINITY IgG that competes with IgE
What are monoclonal antibodies? (3)
- Antibodies made by identical antibody molecules (B lymphocytes producing IgG antibodies) that are CLONES of a unique parent cell
- Produced by hybridoma (hybrid cells produced by fusion of antibody-producing lymphocytes + tumour cell)
- Specificity to one epitope (antibody binding part of antigen)
What are the pros (5) and cons (2) of monoclonal antibodies?
PROS: highly specific for intended target, tailor made with right affinity, stay in blood stream for months, not toxic to body, can be bi-specific
CONS: expensive, side affects can be serious
What can monoclonal antibodies be used for? (4)
Treatment of; cancer, autoimmune disease, infections, prevent coagulation
What is anaphylaxis?
A serious reaction where MAST CELL activation occurs THROUGHOUT THE BODY
Why are allergies and autoimmune diseases more prevalent in industrialised countries?
Th1 cells are not primed at an early age (by a range of microorganisms)
…so Th2 cells overreact (attacking microorganisms that are not necessarily harmful)
