Immediate hypersensitivity type 1 Flashcards
definition of a hypersensitivity reaction
an immune response that causes tissue damage
what immune responses may be defined as hypersensitive?
reaction to foreign Abs or self-Ags
Clinically, hypersensitivity 1 manifests from the actions of
mast cells
Atopy
the tendency of a person to develop allergic diseases
TIHS is triggered by the production of
IgE against environmental Ags
What T cell would we see activated in TIHIS?
Th2: stimulated production of IgE
What cytokine from X group of T cells would we expect to be in high production during a TIHS reaction?
IL-4: stimulates mast cells to produce IgE
Sequence of events leading to TIHS reaction:
- first exposure to antigen
- Antigen activation of Th2 cells, stimulating IgE class switching in B cells
- Production of IgE
- Binding of IgE to Fc(epsilon)RI on mast cells
- 2nd exposure to Ag
- Mast cell activation: mediators released
What do mast cells release?
vasoactive amines, lipid mediators—> immediate hypersensitive reaction in minutes
cytokines–> late phase reaction (6-24 hrs after repeat exposure to allergen)
What physical malady do we expect from a TIHS rxn?
1) Immediate: edema, congestion, vasodilation
2) delated (6-24 hrs after rxn)
Late phase reaction
6-24 hrs after secondary antigen exposure, mediate by cytokines
inflammatory infiltrate rich in eosinophils, neutrophils, T cells
Immediate phase reaction
Edema, vasodilation, congestion
most important mediators produced by mast cells
vasoactive amine (histamine), proteolytic proteases, prostaglandins, leukotrienes, cytokines
histamine –>
dilation of blood vessels, vascular permeability
Proteases–>
damage to local tissue
