The Role of Fever in Immune Defense

Introduction

• Common treatment for fever often involves medication to suppress it.
• Fever is an ancient defense mechanism against diseases.
• Questions to explore: What is fever, its impact on the immune system, and should it be suppressed?

The Heat of Life

• Life thrives between -10°C (in cool pools) and 120°C (in thermal vents).
• Each organism has an ideal and a stressful temperature range.
• Humans maintain a body temperature of ~37°C (98.6°F).
  • This temperature helps make humans mostly immune to fungi, which thrive in cooler hosts.

Fever as a Defensive Mechanism

• Fever acts as a "climate change" for microbes, pushing them out of their comfort zones.
• It is a response seen across many animals, evolved 600 million years ago.
• Fever involves increasing the core body temperature to fight invasions (e.g., bacteria, viruses).

Physiological Process

• Triggered by pyrogens, which increase the body's internal thermostat via the brain.
• Body responses include shivering and constricting surface blood vessels to retain heat.
• Fever requires a significant energy investment, burning 10% more calories per degree Celsius rise in temperature.

Impact on Microbes

• Fever stresses bacteria, causing organ damage, DNA issues, and reduced protein production.
• Virus-infected cells become stressed, producing heat shock proteins (HSPs), leading to their destruction by immune cells.
  • Particularly impacts viruses like the rhinovirus.

Immune System Enhancement

• Fever improves the efficacy of immune cells:
  • Neutrophils, macrophages, dendritic cells work more effectively.
  • Helps the immune system deplete resources needed by invaders.

Adaptation Challenges for Pathogens

• Fever poses an evolutionary dilemma for pathogens.
  • Microbes adapting to fever might struggle to infect new hosts with normal temperatures.
  • Some, like measles, use "hit-and-run" tactics to spread before the fever peaks.

Considerations for Suppressing Fever

• Over-the-counter medications (e.g., ibuprofen) are relatively recent.
• Fever should not necessarily be treated if below 40°C (104°F) unless in specific groups:
  • Pregnant women, seniors, seriously weakened patients.
• Fever above 40°C is dangerous due to potential failure of internal heat regulation.
• Evidence suggests that suppressing fever can prolong illness for diseases like influenza or chickenpox.

Conclusion

• Fever serves as an effective immune response component.
• The decision to suppress fever should consider individual circumstances and involve consultation with a doctor.
• Fever is bearable, often supports defenses, but suppression can offer quick pain relief at a trade-off with immune efficiency.
• Further research is needed to understand fever's role fully.

Additional Information

• Mention of 80,000 Hours, a non-profit offering career advice to make a positive global impact.