Figure 3.

Diagram of the humoral allergic response. This figure outlines the steps of the humoral response. Once the allergen is processed and presented by the APC’s to the Th0 cells, the Th0 cells differentiate into Th2 cells in allergic individuals. Th2 secrete IL-4, IL-5 and IL-13, triggering B-cell differentiation into plasma cells. As a result, they proliferate and produce excessive amounts of allergen-specific IgE that bind to FcεRI receptors on mast cells and basophils. This process is said to sensitize the immune system. Secondary and subsequent exposure to the same allergen (see Figure 3) leads to cross-linking at the FcεRI receptors, triggering the release of mediators such as histamine, causing an allergic inflammation.