CHAPTER SIX: CHRONIC INFLAMMATION
Introduction
We know that inflammation can be acute, subacute or chronic. Generally inflammatory reactions initially are acute, but there are four possible paths, or outcomes, to acute inflammation. of the inflammation. This means that the tissue post-inflammation is the same as it was before the injury and inflammation. 2. The second possible outcome is that the tissue heals through . Scarring refers to the replacement of damaged tissue with connective tissue. 3. The third pathway is formation. An abscess is a contained, circumscribed, localized collection of pus. 4. The fourth option is that acute inflammation progresses to inflammation. 1. The first pathway is complete Chronic inflammation does not always occur as a progression from acute and subacute inflammation. In certain types of injury, chronic inflammation is the first response seen. Chronic inflammation is generally seen in situations where the pathogen is less potent than in acute inflammation but is persistent. Examples of pathogens causing chronic inflammation include:
1. low grade infection with a weak pathogen 2. delayed hyper-sensitivity reactions 3. some autoimmune diseases 4. repeated traumas such as chronic overuse and chronic concussion
Chronic Inflammatory Cells
play an important role in chronic inflammation as they are part of the mononuclear phagocyte system. Recall that macrophages are monocytes residing in body tissues. In the liver, macrophages are called Kupffer cells, in the spleen and lymph nodes they are called sinus histocytes, microglia in the central nervous system (CNS), and alveolar macrophages in the lungs. When in circulation, monocytes have a life span of only a few days, however in tissue, macrophages can live for weeks or months. The role of macrophages is to patrol the tissue and destroy invading pathogens. In chronic inflammation macrophages are more destructive than useful as the presence of pathogen is not common. Instead macrophages destroy tissue cells and promote fibrosis through the release of proteases, cytokines, complement proteins, growth factors and fibrin and fibrinogen.
33
Made with FlippingBook Publishing Software