Overview
This lecture focuses on the components and mechanisms of innate (nonspecific) immunity, distinguishing it from adaptive (specific) immunity, and details the roles of various cells, physical barriers, and chemical defenses.
Types of Immunity
- Innate (nonspecific) immunity is the body's first rapid response to invaders and is always present.
- Adaptive (specific) immunity develops slowly, targets specific pathogens, and involves humoral (antibody-mediated) and cell-mediated (cytotoxic lymphocyte) responses.
- Innate immunity gives the body time to activate adaptive immunity.
Cells Involved in Immunity
- Neutrophils, eosinophils, basophils, and monocytes are crucial for innate immunity.
- Lymphocytes are key for adaptive immunity.
- Remember leukocyte abundance: "Never Let Monkeys Eat Bananas" (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils).
Physical and Chemical Barriers
- Lysozymes in tears and secretions are antibacterial.
- The skin acts as a physical barrier and has acids and normal flora to inhibit microbes.
- Mucus and cilia in the trachea trap and remove particles.
- Stomach acid (pH 2) kills most but not all microbes.
- Skin layers: epidermis (outermost), dermis (innermost); sebaceous glands play a role in immunity.
Inflammation and Its Purpose
- Inflammation occurs in response to tissue damage or microbial invasion.
- Main goals: bring phagocytes to the site, destroy invaders, clear debris, and start healing.
- Macrophages immediately begin phagocytosis at injury sites.
- Mast cells release histamine, causing vasodilation and increased blood flow and heat.
- Increased capillary permeability leads to swelling (edema) and pain.
- More phagocytes reach the tissue, increasing immune responses like fever.
Mechanisms of Defense
- Phagocytosis: form of endocytosis; steps and role of opsonins (to be completed as homework).
- Interferons: proteins released by infected cells to interfere with viral replication in nearby cells.
- Natural killer cells release perforins to lyse infected or cancerous cells.
- Complement system proteins form membrane attack complexes (MACs) that lyse bacteria.
Limitations of Innate Immunity
- Innate immunity is fast and broad but not specific or long-lasting.
- Adaptive immunity is needed for targeted and lasting protection.
Key Terms & Definitions
- Innate Immunity — Immediate, non-specific defense mechanism.
- Adaptive Immunity — Delayed, specific defense involving lymphocytes.
- Lysozyme — Antibacterial enzyme in tears and secretions.
- Inflammation — Tissue response to damage/infection, characterized by redness, heat, swelling, and pain.
- Phagocytosis — Ingestion and destruction of pathogens by cells.
- Opsonins — Molecules that enhance phagocytosis.
- Interferon — Protein that inhibits viral replication.
- Natural Killer Cell — Lymphocyte-like cell that kills infected/cancerous cells.
- Perforins — Molecules that create pores in target cell membranes.
- Complement System — Plasma proteins that lyse microbes via membrane attack complexes (MAC).
Action Items / Next Steps
- Use the provided flow chart as a road map for innate vs. adaptive response.
- Identify the function of sebaceous glands in the immune response using the textbook.
- Fill in the steps of phagocytosis as outlined in class notes.
- Research why opsonins are important in phagocytosis.
- Read additional functions of interferons as per the textbook.