Fever: Videos & Practice Problems

Fever, defined as a body temperature above 37.8°C, is an innate immune response that helps eliminate pathogens. The hypothalamus regulates body temperature, and elevated temperatures inhibit bacterial growth while enhancing inflammatory responses through increased enzymatic activity. Pyrogens, which can be endogenous or exogenous, induce fever. Although fever can cause discomfort, it is a protective mechanism that accelerates the body's ability to fight infections, making it a crucial aspect of innate immunity.

Fever

Fever is an innate immune response characterized by an abnormally high body temperature, specifically above 37.8 degrees Celsius (100 degrees Fahrenheit). This physiological change is part of the second line of defense in innate immunity, aimed at eliminating pathogens. The hypothalamus, a region in the brain, acts as the body's temperature-regulating center, maintaining normal body temperature around 37 degrees Celsius.

Elevated body temperatures associated with fever can inhibit the growth of most bacteria, serving as a protective mechanism against infections. Additionally, fever enhances the body's protective functions by increasing the inflammatory response and the release of inflammatory cytokines, which are crucial for combating microbes. The rise in temperature accelerates enzymatic reactions, allowing the immune system to respond more effectively to infections.

The term pyrogens refers to substances that induce fever. These can be classified as endogenous pyrogens, produced within the body, or exogenous pyrogens, originating from external sources. Understanding the role of pyrogens is essential in recognizing how the body responds to infections.

In summary, while fever may cause discomfort, it is a vital response that aids in the elimination of pathogens and enhances the overall immune response. This innate effector action is a key component of the body's defense mechanisms, illustrating the complex interplay between temperature regulation and immune function.

Lipopolysaccharide (LPS) is an endotoxin created by some gram-negative (-) bacteria that commonly causes fever in humans. Lipopolysaccharide is what type of molecule?

• A. Endogenous pyrogen.
• B. Exogenous pyrogen.
• C. Pathogenic pyrogen.
• D. External pyrogen.

Answer: (B)

Fever can have positive effects on the process of fighting an infection. Which of these answers is not a positive effect fever can have during an infection?

• A. High body temperatures inhibiting the growth of many pathogenic bacteria.
• B. High body temperatures increase the enzymatic reactions associated with the immune system.
• C. High body temperatures enhance the inflammatory response and release of inflammatory signals.
• D. High body temperatures constrict the blood vessels ensuring the infection does not spread throughout the body.

Answer: (D)

Here’s what students ask on this topic:

What is the role of the hypothalamus in regulating body temperature during a fever?

The hypothalamus acts as the body's temperature-regulating center. During a fever, pyrogens (fever-inducing cytokines) signal the hypothalamus to raise the body's set point temperature above the normal 37°C. This elevated set point leads to an increase in body temperature, which helps inhibit bacterial growth and enhances the body's immune response. The higher temperature accelerates enzymatic reactions, boosting the inflammatory response and the release of cytokines, thereby aiding in the elimination of pathogens.

How do pyrogens induce fever, and what are the differences between endogenous and exogenous pyrogens?

Pyrogens are substances that induce fever by signaling the hypothalamus to raise the body's temperature set point. Endogenous pyrogens are produced within the body, typically by immune cells in response to infection. Examples include cytokines like interleukin-1 (IL-1) and tumor necrosis factor (TNF). Exogenous pyrogens originate outside the body, such as bacterial toxins. Both types of pyrogens trigger the hypothalamus to increase body temperature, aiding in the immune response by inhibiting pathogen growth and enhancing immune functions.

Why is fever considered a beneficial response in the immune system?

Fever is beneficial because it creates an environment less favorable for bacterial growth and enhances the body's immune response. Elevated temperatures inhibit the replication of many pathogens and increase the rate of enzymatic reactions, which boosts the inflammatory response and the release of cytokines. This accelerated immune activity helps the body eliminate infections more efficiently. Although fever can cause discomfort, it is a protective mechanism that supports the body's efforts to fight off pathogens.

What are the potential risks associated with high fever?

While fever is generally a protective response, excessively high body temperatures can be dangerous. Prolonged high fever can lead to dehydration, electrolyte imbalances, and in severe cases, febrile seizures, especially in young children. Extremely high fevers (above 40°C or 104°F) can cause damage to body tissues and organs, leading to complications such as brain damage. Therefore, it is important to monitor fever and seek medical attention if it becomes excessively high or persistent.

How does fever enhance the inflammatory response?

Fever enhances the inflammatory response by increasing the rate of enzymatic reactions in the body. Higher temperatures accelerate the production and activity of inflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF). These cytokines promote the recruitment of immune cells to the site of infection, increase vascular permeability, and stimulate the production of acute-phase proteins. This heightened inflammatory response helps to contain and eliminate pathogens more effectively.