Chapter 22: Innate Non-Specific Host Resistance

Introduction

• Focus on innate non-specific mechanisms in humans.
• Resistance to parasitic relationships through non-specific and specific mechanisms.
• Innate immunity is inherited and lacks memory; it responds in the same way each time.
• Specific (adaptive) immunity has memory and improves with exposure.

Key Terms

• Immunity: Host's ability to resist disease.
• Immunology: Science of immune responses.
• Antigens: Substances that elicit an immune response.

Types of Immunity

• Innate Immunity: Non-specific, general resistance inherent to the organism.
  • Present in animals and plants.
  • Lacks memory.
• Adaptive Immunity: Specific resistance involving antibodies and memory.
  • Involves bridges like dendritic cells linking innate and adaptive responses.

Physical Barriers

• Skin: Thick, densely packed cells.
  • Contains acidity and salt to deter microbes.
• Mucous Membranes: Secrete mucus forming a protective covering.
  • Contain antibacterial substances.

Cells and Tissues Involved

• Lymphoid Tissue: Includes primary (bone marrow, thymus) and secondary (spleen, lymph nodes) tissues.
• White Blood Cells (Leukocytes): Derived from pluripotent stem cells.
  • Granulocytes: Basophils, eosinophils, and neutrophils.
  • Monocytes and Macrophages: Engulf and destroy pathogens.
  • Dendritic Cells: Antigen-presenting cells.
  • Natural Killer Cells: Destroy infected and malignant cells.

Chemical Mediators

• Antimicrobial Peptides: Cationic peptides like cathelicidins, defensins, and histatins.
• Complement System: Serum proteins that aid in opsonization, bridging immunity types, and waste removal.
  • Pathways: Alternative, lectin, and classical.

Cytokines

• Proteins or glycoproteins acting as mediators.
• Types include interleukins, chemokines, interferons, etc.

Phagocytosis

• Process where cells engulf and destroy pathogens.
• Involves recognition, ingestion, and intracellular digestion.

Inflammation

• Non-specific response to injury.
  • Characterized by redness, heat, pain, and swelling.
• Chronic inflammation involves a dense infiltration of immune cells and granuloma formation.

Summary

• Understanding innate immunity provides insight into the first line of defense against pathogens.
• The chapter covers the various components and their roles in maintaining host defense.