The immune system is exceedingly complex in its constituent cells, molecules, and signaling pathways. Each major component of the immune system is critical for survival; immune activity protects against infections that would quickly be lethal without immune defenses and eliminates cells in the stages of cancerous transformation.
The most common and major immune system disorders are related to an immune activity that exceeds physiological needs. Hypersensitivity in the form of allergies occurs in 10% to 20% of the population. The prevalence of allergies increased in the developed world from the 1960s through the early 2000s, after which it began to plateau. Although less common than immune hyperactivity, disorders in which immune activity is below normal leave an individual susceptible to dangerous infections. In some individuals, immune activity is compromised to the extent that those affected are at risk for a major illness or even death.
1. What is the “big picture” of the immune system’s role in maintaining homeostasis?
2. What general principles are involved in the protection provided by the innate and adaptive immune systems?
The annual incidence of cancer in the United States is estimated at 439.2 per 100,000 persons, with an annual rate of deaths due to cancer of 163.5 per 100,000 persons. Cancer ranks second, just behind heart disease, as a cause of death in the United States.
Over the past 25 years, death rates have dropped in the United States for cancers of the lung and bronchus, prostate, colon and rectum, and stomach, while liver cancer death rates have increased. At least 42% of cancer cases in the United States may be preventable with lifestyle changes such as smoking cessation, weight loss, physical activity, alcohol use reduction or avoidance, improved nutrition, use of sunblock, and avoidance of tanning devices. Vaccination or antibiotic use can reduce the incidence of cancer-causing infections such as those due to hepatitis B and C viruses, human papillomavirus, and Helicobacter pylori.
1. What features help to differentiate a benign tumor from a malignant tumor?
2. What tissues give rise to a carcinoma, a sarcoma, and a lymphoma?
