Effects of Inflammation

The effects of inflammation can be both local and systemic. The systemic effects of acute inflammation include fever, leukocytosis and vascular changes. These will be discussed in more detail later in this unit. The local effects are usually clearly beneficial, for example the destruction of invading microorganism, but at other times they appear to serve no obvious function, or may even be harmful.

Beneficial effects

Both the fluid and cellular exudates may have useful effects. Beneficial effects of the fluid exudate are as follows:

Entry of antibodies. Increased vascular permeability allows antibodies to enter the extravascular space, where they may lead either to lysis of microorganisms, through the participation of complement, or to phagocytosis by opsonization. Antibodies are also important in neutralization of toxins.

Fibrin formation. Fibrin formation from exuded fibrinogen may mechanically impede the movement of micro-organisms, trapping them and so facilitating phagocytosis.

Stimulation of immune response. The drainage of this fluid exudate into the lymphatics allows particulate and soluble antigens to reach the local lymph nodes where they may stimulate the immune response.

Harmful effects

As we all know however, the inflammatory response has significant harmful effects. Most of these are caused by release of lysosomal enzymes by inflammatory cells. Some of these harmful effects include:

Destruction of normal tissues. Enzymes such as collagenases, elastases and other proteases may degrade normal tissues, resulting in their destruction. For example in type III hypersensitivity reactions and in some types of glomerulonephritis small vessels are damaged.

Swelling. The swelling of acutely inflamed tissues may be harmful. At right is a dog with a swollen face due to an anaphylactic reaction. If that swelling occurs in the larynx, VERY BAD. Inflammatory swelling is especially serious when it occurs in an enclosed space such as the cranial cavity. Thus, acute meningitis or an intra-cerebral abscess may raise intracranial pressure to the point where blood flow into the brain is impaired, resulting in cerebral edema, or may force the cerebral hemispheres against the tentorial orifice and the cerebellum into the foramen magnum (cerebellar herniation).

Inappropriate inflammatory response. Sometimes, acute inflammatory responses appear inappropriate, such as those which occur in type I hypersensitivity reactions where the provoking environmental antigen (e.g. pollen) otherwise poses no threat to the individual.


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