Lecture 01: First Line of Defense in Immunology [Quiz 2]

Which component of the skin contributes to its ability to block pathogens?

Which of the following is NOT a characteristic of innate immunity?

What is the role of lysozymes found in saliva?

What action do antimicrobial peptides (AMPs) perform against bacterial cells?

Which factor contributes to the acidity of the skin that helps prevent infection?

Which cell type is primarily involved in acquired immunity?

What mechanism do exfoliation and constant shedding of skin cells serve in the immune response?

Which factor indicates the effectiveness of the skin as a barrier against pathogens?

Which response mechanism is initiated by the presence of a pathogen at epithelial linings?

What is the consequence of the slightly acidic pH of the skin?

First Line of Defense

Physical Barriers:
- Skin: A tough, multilayered barrier. The outer layer (epidermis) contains dead keratinocytes, and the dermis contains immune cells.
- Epithelial Linings: Mucous membranes (e.g., nose, throat, intestines) trap pathogens with mucus and cilia. Expulsive reflexes (coughing, sneezing, vomiting) further remove pathogens.
- Normal Microflora: Compete with pathogens for resources, preventing their colonization.
Chemical Barriers:
- pH: Slightly acidic skin pH and high stomach acidity inhibit microbial growth. High salt concentration in sweat also inhibits microbial growth.
- Enzymes: Lysozymes in saliva and other secretions break down peptidoglycan in bacterial cell walls, leading to cell lysis.
- Antimicrobial Peptides (AMPs): Present in skin and saliva. These peptides target bacterial membranes, disrupting them and causing cell death. Examples include psoriasin, defensins (alpha and beta), and lactoferrin.
  - Psoriasin: Disrupts membranes and sequesters zinc.
  - Defensins: Create pores in bacterial membranes, leading to cell death.
  - Lactoferrin: Binds iron, depriving bacteria of a crucial nutrient. (Note: Cleaved into smaller AMPs).

Innate Immunity

Components:
- Macrophages, Natural Killer (NK) cells, and dendritic cells.
Characteristics: Rapid, non-specific responses.

Acquired Immunity

Components:
- Lymphocytes: B cells and T cells
Characteristics: Slow, long-lasting, and highly specific responses.

Explore the crucial physical and chemical barriers that form the body's first line of defense against pathogens. This quiz delves into the roles of skin, epithelial linings, and normal microflora, as well as the chemical defenses like pH and enzymes. Test your knowledge on how these mechanisms work together to protect us from infections.