Immediate hypersensitivity: An exaggerated immune response mediated by antibody (type I and
II) or antigen-antibody complexes (type III) that manifests within minutes to hours after
exposure of a sensitized individual to antigen.
Delayed-type hypersensitivity (DTH):Atype IV hypersensitive response mediated by sensitized
TH cells, which release various cytokines and chemokines. The response generally occurs 2 to 3
days after TH cells interact with antigen.
Some people, referred to as atopic, are predisposed to generate IgE (mainly memory antibodies)
antibodies against common environmental antigens.
- Many allergens have enzymatic activities that affect immune response
- Many allergens have PAMPs
- Third, many allergens enter the host via mucosal tissues at very low concentrations,
which tend to predispose the individual to generate TH2 responses, leading to B-cell
secretion of IgE.
- Present on mast cells, easinophils, and basophils
- Binding of Ig to these receptors results in the degranulation of cells
- These mediators act on surroun