General Pathology: Inflammation and Repair Quiz

Systemic Reactions

• Fever is a protective host response, characterized by an elevation of body temperature, often associated with infection.
• Pyrogens, such as bacterial products (exogenous pyrogens) and cytokines (endogenous pyrogens), induce fever.
• IL-1 and TNF act by stimulating the release of endogenous pyrogens, which upregulate cyclooxygenases to synthesize prostaglandins.
• Prostaglandins, primarily PGE2, synthesized by vascular and perivascular cells of the hypothalamus, stimulate the production of neurotransmitters to reset the body's steady-state temperature.

Acute-Phase Proteins

• Elevated levels of acute-phase proteins, such as C-reactive protein (CRP), fibrinogen, and serum amyloid A (SAA) protein, are synthesized in the liver.

Inflammation

• Inflammation is a protective response to tissue injury or infection, characterized by the 5 'R's: redness, swelling, heat, pain, and loss of function.
• Causes of inflammation include physical, chemical, biological, and immune-mediated injuries.

Acute Inflammation

• Vasodilation and increased blood flow lead to increased vascular permeability and stasis.
• Recruitment of leukocytes to sites of inflammation involves margination, rolling, adhesion, migration, and chemotaxis.
• Removal of offending agents via phagocytosis involves recognition and attachment, engulfment, and intracellular destruction.
• Endothelial and neuronal NOS are constitutively expressed at low levels, while iNOS is involved in microbial killing and induced when macrophages +/- neutrophils are activated.

Leukocyte-Mediated Tissue Injury

• Leukocyte-mediated tissue injury occurs via the release of lysosomal enzymes, such as MPO, bactericidal proteins, acid hydrolases, and neutral proteases.
• Macrophages also contain acid hydrolases, collagenase, and elastase, which degrade bacteria, debris, extracellular matrix components, and complement proteins.

Morphologic Patterns of Acute Inflammation

• General morphologic features include vascular dilation and congestion, edema, and inflammatory cellular infiltrate within the extravascular tissue.
• Specific morphologic patterns include serous inflammation, fibrinous inflammation, suppurative (purulent) inflammation, and ulcers.

Outcomes of Acute Inflammation

• Three possible outcomes of acute inflammation: complete resolution, scarring/fibrosis, and chronic inflammation.
• Complete resolution is the ideal outcome, where injury is limited, and removal of cellular debris and microbes by macrophages occurs, allowing for regeneration of damaged cells.