Some Cytokines Are Important Inflammatory Mediators

A number of cytokines play a significant role in the development of an acute or chronic inflammatory response. IL-1, IL-6, TNF-a, IL-12, and many chemokines exhibit redundant and pleiotropic effects that together contribute to the inflammatory response. Some of the effects mediated by IL-1, IL-6, and TNF-a are listed in Table 15-3. In addition, IFN-7 contributes to the inflammatory response, acting later in the acute response and contributing in a major way to chronic inflammation by attracting and activating macrophages. IL-12 induces the differentiation of the proinflammatory TH1 subset. The role of several of these inflammatory cytokines in the development of acute and chronic inflammation will be described more fully in the next section.

Membrane phospholipids

Phospholipase

Arachidonic acid

Cyclooxygenase pathways

Prostaglandin G2

Arachidonic acid

Cyclooxygenase pathways

Lipoxygenase pathway

Lipoxygenase pathway

Leukotriene A4

Thromboxane

Prostaglandins

Leukotrienes C4, D4, E4

Leukotriene B4

Lyso-PAF

Thromboxane

Prostaglandins

Leukotrienes C4, D4, E4

Leukotriene B4

Vasoconstriction

Î Vascular permeability

SRS-A

Neutrophil

Platelet aggregation

Platelet aggregation

Vascular dilation

Bronchial smooth-

chemotaxis

Eosinophil chemotaxis

Other effects

Neutrophil chemotaxis Other effects

muscle contraction

Neutrophil activation

FIGURE 15-11

The breakdown of membrane phospholipids generates important mediators of inflammation, including thromboxane, prostaglandins, leukotrienes, and platelet-activating factor (PAF).

FIGURE 15-11

The breakdown of membrane phospholipids generates important mediators of inflammation, including thromboxane, prostaglandins, leukotrienes, and platelet-activating factor (PAF).

TABLE 15-3

Redundant and pleiotropic effects of IL-1, TNF-a, and IL-6

Effect

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