Hypersensitivity Part 1 lecture 8 Flashcards
Hypersensitivity
immunity as sensitivity. Based on the observation than an individual who has been exposed to an antigen exhibits detectable reaction
Gell and Coombs
1960s
applied to drug hypersensitivity reactions
the role of T lymphocytes, MHC restriction, and cytokines were largely unknown
despite that, system persisted
Immediate type I
Mediated by IgE antibody
mast cell, eosinophils and their mediation (vaso active amines, lipid mediation, cytokines)
Atopy: unusual but really not so unusual now.
antibody mediated: type II
IgM, IgG antibodies against cell surface or extracellular matrix antigens
Opsonization mediated phagocytosis of cells
complement and Fc receptor mediated recruitment and actiation of leukocytes. Abnormalities in cellular function (hormone receptor signaling, neurotransmitter receptor blockade
Immune complex mediated: Type III
Immune complex of circulating antigens and IgM or IgG antibodies
Bind to antigens that are soluble and causes a complex to deposit in diferent tissues. Complement or Fc mediated recruitment of leukocytes
T cell mediated: Type VI
- Cd4T cells (Th1 and Th17)
- CD8 CTLs
Cytokine mediated inflammation and direct target cell killing cytokine-mediated inflammation
Sensitization
Developing the immediate type reaction. Not necessarily sure when they develop this. Maybe getting the allergen through the skin instead of orally and the development of that allergy will occur.
IL4 induces class switching to IgE
IgE bind to Fc epsilon Receptor
Activation of mast cells
repeat exposure to allergen occurs
activation of mast cells: release of mediators
Immediate hypersensitivity reaction (mins)
late phase reaction (6-24 hours) after repeat exposure to allergen
Release of mast cell mediators TYpe I
Histamine/lipid mediators: Vascular smooth muscle responses
Inflammation in the late phase
Biological effects of mast cell mediators Type I
biogeni amines (histamine) and lipid mediators (PAF, PGD2, LTC): vasodilation, vascular leak, broncho constriction, intestinal hypermotility
Cytokine and lipid mediators: inflammation
Late phase reaction Type I
IL5 from mast cells and Th2 cells recruit and activate eosinophils (parasitic infections)
disease associations type I
allergic rhinitis, allergic asthma, eczema or atopic dermatitis, food allergy, drug allergy, insect venom allergy
localized reactions
allergic rhinitis sinusitis (hay fever): increased mucus secretion; inflammation of upper airway sinuses
systemic anaphylaxis
heart and vascular system: increased capillary permeability, entry of fluid to tissue, swelling, low BP.
respiratory tract: contraction of smooth muscles and constriction of smooth airways. Difficulty in swallowing, bloating, and wheezing
gastrointestinal tract: contraction of smooth muscle, diarrhea
allergic march
progression of allergic symptoms with age
chronic asthmatics have atopic dermatitis
sensitivity to food in infants can be associated with appearance of allergy to inhalants later in life