The early response occurs within minutes of allergen exposure and results from the release of
histamine (vasodilation), leukotrienes (bronchoconstriction), and prostaglandins (mucus
secretion) from local mast cells.
In the late-phase reaction, cytokines released from mast cells, particularly TNF-α and IL-1,
increase the expression of cell adhesion molecules on venular endothelial cells, thus facilitating
the influx of neutrophils, eosinophils, and TH2 cells that characterizes this phase of the response.
Eosinophils play a principal role in the late-phase reaction. Eosinophil chemotactic factor,
released by mast cells during the initial reaction, attracts large numbers of eosinophils to the
affected site. This leads to degran