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Microbiology, 2021

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768 19 • Diseases of the Immune System<br />

Selected Preformed Components of Mast Cell Granules<br />

Granule<br />

Component<br />

Activity<br />

Serotonin<br />

Increases vascular permeability, causes vasodilation and smooth-muscle contraction<br />

Table 19.1<br />

Selected Newly Formed Chemical Mediators of Inflammation and Allergic Response<br />

Chemical<br />

Mediator<br />

Activity<br />

Leukotriene<br />

Prostaglandin<br />

TNF-α (cytokine)<br />

Causes smooth-muscle contraction and mucus secretion, increases vascular<br />

permeability<br />

Causes smooth-muscle contraction and vasodilation<br />

Causes inflammation and stimulates cytokine production by other cell types<br />

Table 19.2<br />

Figure 19.3 On first exposure to an allergen in a susceptible individual, antigen-presenting cells process and present allergen epitopes<br />

with major histocompatibility complex (MHC) II to T helper cells. B cells also process and present the same allergen epitope to T H 2 cells,<br />

which release cytokines IL-4 and IL-13 to stimulate proliferation and differentiation into IgE-secreting plasma cells. The IgE molecules<br />

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