Chapter 3: Inflammation and Repair
- Inflammation is a response of vascularized tissues to infections and tissue damage that
brings cells and molecules of host defense from the circulation to the sites where they
are needed, to eliminate the offending agents
- The typical inflammatory reaction develops through a series of sequential steps:
1) The offending agent, which is located in extravascular tissues, is recognized by host
cells and molecules.
2) Leukocytes and plasma proteins are recruited from the circulation to the site where
the offending agent is located.
3) The leukocytes and proteins are activated and work together to destroy and
eliminate the offending substance.
4) The reaction is controlled and terminated
5) The damaged tissue is repaired.
- The rapid response to infections and tissue damage is called acute inflammation. It
typically develops within minutes or hours and is of short duration
- Chronic inflammation may follow acute inflammation. It is of longer duration and is
associated with more tissue destruction, the presence of lymphocytes and macrophages,
the proliferation of blood vessels, and fibrosis
- When a microbe enters a tissue or the tissue is injured, the presence of the infection or
damage is sensed by resident cells, including macrophages, dendritic cells, mast cells,
and other cell types. These cells secrete molecules (cytokines and other mediators) that
induce and regulate the subsequent inflammatory response. Inflammatory mediators are
produced which promote the efflux of plasma and the recruitment of circulating
leukocytes to the site. Mediators also activate the recruited leukocytes, enhancing their
ability to destroy and remove the offending agent
- The external manifestations of inflammation, often called its cardinal signs, are heat
(calor in Latin), redness (rubor), swelling (tumor), pain (dolor), and loss of function
(functio laesa).
Causes of inflammation
Infections (bacterial, viral, fungal, parasitic)
Tissue necrosis elicits inflammation regardless of the cause of cell death, which may
include ischemia (reduced blood flow, the cause of myocardial infarction), trauma,
and physical and chemical injury (e.g., thermal injury, as in burns or frostbite;
irradiation; exposure to some environmental chemicals)
Foreign bodies may elicit inflammation by themselves or because they cause
traumatic tissue injury or carry microbes
Immune reactions are reactions in which the normally protective immune system
damages the individual’s own tissues
Recognition of microbes and damaged cells
- The first step in inflammatory responses is the recognition of microbes and necrotic cells
by cellular receptors and circulating proteins
- Cellular receptors for microbes: epithelial cells, tissue macrophages, leukocytes,
phagocytes, dendritic cells etc. Toll-like receptors (TLRs) recognize PAMPs →
- Inflammation is a response of vascularized tissues to infections and tissue damage that
brings cells and molecules of host defense from the circulation to the sites where they
are needed, to eliminate the offending agents
- The typical inflammatory reaction develops through a series of sequential steps:
1) The offending agent, which is located in extravascular tissues, is recognized by host
cells and molecules.
2) Leukocytes and plasma proteins are recruited from the circulation to the site where
the offending agent is located.
3) The leukocytes and proteins are activated and work together to destroy and
eliminate the offending substance.
4) The reaction is controlled and terminated
5) The damaged tissue is repaired.
- The rapid response to infections and tissue damage is called acute inflammation. It
typically develops within minutes or hours and is of short duration
- Chronic inflammation may follow acute inflammation. It is of longer duration and is
associated with more tissue destruction, the presence of lymphocytes and macrophages,
the proliferation of blood vessels, and fibrosis
- When a microbe enters a tissue or the tissue is injured, the presence of the infection or
damage is sensed by resident cells, including macrophages, dendritic cells, mast cells,
and other cell types. These cells secrete molecules (cytokines and other mediators) that
induce and regulate the subsequent inflammatory response. Inflammatory mediators are
produced which promote the efflux of plasma and the recruitment of circulating
leukocytes to the site. Mediators also activate the recruited leukocytes, enhancing their
ability to destroy and remove the offending agent
- The external manifestations of inflammation, often called its cardinal signs, are heat
(calor in Latin), redness (rubor), swelling (tumor), pain (dolor), and loss of function
(functio laesa).
Causes of inflammation
Infections (bacterial, viral, fungal, parasitic)
Tissue necrosis elicits inflammation regardless of the cause of cell death, which may
include ischemia (reduced blood flow, the cause of myocardial infarction), trauma,
and physical and chemical injury (e.g., thermal injury, as in burns or frostbite;
irradiation; exposure to some environmental chemicals)
Foreign bodies may elicit inflammation by themselves or because they cause
traumatic tissue injury or carry microbes
Immune reactions are reactions in which the normally protective immune system
damages the individual’s own tissues
Recognition of microbes and damaged cells
- The first step in inflammatory responses is the recognition of microbes and necrotic cells
by cellular receptors and circulating proteins
- Cellular receptors for microbes: epithelial cells, tissue macrophages, leukocytes,
phagocytes, dendritic cells etc. Toll-like receptors (TLRs) recognize PAMPs →
