Hypersensitivity I Flashcards
Humoral?
Ig
B cells
T cells can be involved in humoral or CMI but its the final effector function that defines the type of immunity that is involved
CMI?
cellular
Cells
T cells
Four major classes of hypersensitivities…. Gel and Coombs classifications
..
Type I hypersensitivity?
immediate hypersensitivity
type II hypersensitivity?
antibodies bound to cells or tissues
type III hypersensitivity?
immune complex
type IV hypersensitivity?
delayed type hypersensitivity (DTH)
which hypersensitivities are ab-mediated?
Type I, II, III
which hypersensitivities are cell mediated?
Type IV - delayed type hypersensitivity (DTH)
type I - immediate hypersensitivity
pathologic immune mechanism?
mechanisms of tissue injury and disease?
Th2 cells, IgE ab, mast cells, eosinophils
mast cell - derived mediators (vasoactive amines, lipid mediators, cytokines)
type II - ab mediated diseases
pathologic immune mechanism?
mechanisms of tissue injury and disease?
IgM, IgG antibodies against cell surface or extracellular matrix ag
complement and Fc receptor mediated recruitment and activation of leukocytes (neutrophils, macrophages)
opsonization and phagocytosis of cells
abnormalities in cellular funciton, e.g. hormone receptor signaling
type III - immune complex mediated diseases
pathologic immune mechanism?
mechanisms of tissue injury and disease?
immune complexes of circulating age and IgM or IgG abs deposited in vascular basement membrane
complement and Fc receptor-mediated recruitment and activation of leukocytes
type IV - T cell mediated diseases
pathologic immune mechanism?
mechanisms of tissue injury and disease?
- Cd4+ T cells (cytokine-mediated inflamm)
- Cd8+ CTLs ( t cell-mediated cytolysis)
- macrophage activation, cytokine-medaited inflamm
- direct target cell lysis, cytokine-mediated inflamm
Th2 type responses drive….
IgE ab production.
Most of IgE is bound to what?
high affinity Fc receptors on mast/basophils
repeat exposure to an allergen (cross-linking) of mast cells induces degranulation. The degranulation leads to the symptoms of the immediate run of the allergic response. The mast cell is activated to synthesize new mediators which make up the late phase reaction (6-24 hrs after repeat exposure to allergen).
…
atopy/atopic?
prone to developing allergies due to IgE
In the late phase reaction, there is recruitment of eosinophils and T cells and neutrophils.
..
the immediate reaction results in edema and vascular congestion
…
a number of substances are released upon degranulation, the most prominent of which is histamine, which leads to…
vasodilation (edema) and smooth muscle contraction
most important late phase reactants?
prostaglandins and leukotrienes (similar to histamine) and cytokine synthesis (TNF is important for inflamm)
IL-4 is made - reinforces the Th2 response
late phase reaction requires de novo synthesis!!!
- leukotrienes
- cytokines (TNF-alph, IL-4, IL-5)
…
Types of diagnostic tests used for Type I hypersensitivity?
- measurement of IgE levels (relatively nonspecific tho)
- measure for specific IgE Abs against specific allergens
- skin tests - look for “wheal and flare rxn”
Wheel and flare
subQ ag, low dose
mast cell activation
increased vascular permeability leads to localized swelling
have injection sites for allergen, saline, histamine
common sources of allergens….
inhaled materials?
type I
plant pollens
dander of domesticated animals
mold spores
feces of very small animals (house dust mites)
common sources of allergens…
injected materials?
Type I
insect venoms
vaccines
drugs
therapeutic proteins