Notes on Fever and Immune Response

Introduction to Fever

• Fever is a defensive response against disease.
• Raises questions about the efficacy of suppressing it with medication.

The Heat of Life

• Life thrives in a specific temperature range.
• Humans maintain an internal temperature around 37°C (98.6°F).
• This temperature helps protect against fungi, a significant threat to colder animals.

What Is Fever?

• Fever is an evolutionary adaptation, evolved over 600 million years ago.
• Acts as a 'defensive climate change' to push pathogens out of their ideal temperature range.
• Common amongst many animals (e.g., fish, lizards, bees) which seek warmth when sick.

Mechanism of Fever

• Triggered by pyrogens, which signal the brain to increase body temperature.
• Body's response:
  • Shivering to generate heat.
  • Blood vessels constrict to retain heat.
  • Increased metabolic rate (10% more calories burned for each degree Celsius rise).
  • Encourages rest to conserve energy for the immune system.

Effects of Fever on Pathogens and Immune Cells

• Fever stresses invading bacteria, disrupting their reproduction.
• Immune system benefits:
  • Increased speed of neutrophil recruitment.
  • Enhanced function of macrophages and dendritic cells.
  • Encourages nutrient scarcity for pathogens (iron, glucose, glutamine).
• Viruses are similarly affected; notably, rhinovirus thrives at cooler temperatures.

Heat Shock Proteins (HSPs)

• Cells under stress from heat produce HSPs to repair damage.
• High levels of HSPs signal Natural Killer Cells to eliminate infected cells.

Evolutionary Implications of Fever

• Pathogens may adapt to survive higher temperatures but face challenges in infecting healthy hosts later.
• Example of measles: replicates quickly before fever peaks, causing damage before immune response kicks in.

Suppressing Fever: Should You?

• Pain medication (e.g., Aspirin, Ibuprofen) became widely available only recently.
• Pain and fever are interlinked; treatment can mask symptoms but may hinder immune response.
• Non-dangerous fever (below 40°C or 104°F) generally doesn’t require treatment.
• Vulnerable populations (pregnant women, seniors) may need careful monitoring.
• High fevers (over 40°C) could indicate a malfunction in the body’s temperature regulation.
• Some studies suggest that individuals with fever may have better survival rates with certain infectious diseases.

Conclusion

• Consult a doctor regarding fever suppression.
• If fever is manageable, it may aid in faster recovery; if discomfort is severe, medication may provide relief at the cost of immune efficacy.
• Understanding fever enhances knowledge of the immune response against pathogens.