Innate Immune Response Study Notes Chapter 14 PowerPoint

Innate Immune Response

Overview

  • Chapter 14 outlines the innate immune system, contrasting it with adaptive immunity, and discusses key components and processes.

Key Features of Innate vs. Adaptive Immunity

  1. Level of Specificity

    • Innate: Non-specific (recognizes broad patterns).

    • Adaptive: Highly specific (targets specific pathogens).

  2. Timing

    • Innate: Immediate response (hours).

    • Adaptive: Delayed response (days to weeks).

  3. Development of Memory Responses

    • Innate: No memory; response does not improve with subsequent exposure.

    • Adaptive: Provides memory; response is more robust upon re-exposure to the same pathogen.

Physical Barriers in the Innate Immune System

  1. Characteristics

    • First line of defense against pathogens.

  2. Types of Cells

    • Innate immune cells involved in physical barrier functions include epithelial cells, phagocytes, and others.

Chemical Components of the Innate Immune System

  1. Lysozyme

    • Enzyme found in tears, saliva, and other secretions; degrades peptidoglycan.

  2. Lactoferrin

    • Iron-binding protein that sequesters iron, limiting microbial growth.

  3. Defensins

    • Antimicrobial peptides that disrupt microbial membranes.

Benefits of Normal Microflora

  1. Competitive Exclusion of Pathogens

    • Normal flora outcompetes pathogens for resources.

  2. Covering Attachment Sites

    • Prevents pathogens from adhering to epithelial surfaces.

  3. Producing Toxic Compounds

    • Some microbiota produce bacteriocins and other antimicrobial substances.

  4. Supporting Immune Function

    • Promotes the development of immune responses, particularly in infants.

Hematopoiesis

  1. Definition

    • The process of forming blood cellular components.

  2. Responsibility

    • Produces various immune cells from hematopoietic stem cells.

Progenitor Cell Types

  1. Myeloid Progenitor Cells

    • Give rise to granulocytes and monocytes.

    • Include neutrophils, basophils, eosinophils, and others.

  2. Lymphoid Progenitor Cells

    • Develop into lymphocytes (B cells, T cells, NK cells).

Granulocytes and Their Roles

  1. Cells Making Up Granulocytes

    • Neutrophils: Primary phagocytic cells, most abundant.

    • Basophils: Involved in allergic responses, release histamine.

    • Eosinophils: Combat parasitic infections and contribute to allergic reactions.

  2. Polymorphonuclear Cells (PMNs)

    • Term used for granulocytes due to their multi-lobed nuclei.

Monocyte-Derived Cells

  1. Types

    • Macrophages: Found throughout the body, specialize in phagocytosis.

    • Dendritic Cells: Capture antigens and present them to lymphocytes.

  2. Functions

    • Both play critical roles in both innate and adaptive immunity.

Cytokines and Cell Communication

  1. Importance of Cytokines

    • Mediate communication between immune cells.

  2. Major Classes of Cytokines

    • Pro-inflammatory cytokines: such as TNF-alpha, IL-1, and IL-6, which promote inflammation.

Interferon and Antiviral Proteins (iAVPs)

  1. Definition of iAVPs

    • Inactive antiviral proteins activated during viral infections to inhibit viral replication.

  2. Role in Viral Response

    • Degrade RNA and inhibit protein synthesis upon activation by viral signals.

Complement Cascade Outcomes

  1. Three Major Outcomes

    • Inflammation: C3a and C5a increase vascular permeability and attract phagocytes.

    • Lysis of Foreign Cells: Membrane attack complexes form to disrupt microbial membranes.

    • Opsonization: C3b coats pathogens, marking them for phagocytosis.

Phagocytosis Overview

  1. Basic Steps

    • Chemotaxis: Phagocytes are recruited to the site of infection.

    • Recognition and Attachment: Binding of phagocytes to pathogens via receptors.

    • Engulfment: Formation of phagosome around the ingested particle.

    • Fusion with Lysosome: Digestion occurs in phagolysosome.

    • Exocytosis: Removal of debris from the cell.

  2. Comparison of Macrophages vs. Neutrophils

    • Macrophages: Long-lived and perform routine debris clearance, as well as participate in adaptive immunity.

    • Neutrophils: Short-lived; early responders, and capable of rapid and destructive activity.

Inflammation

  1. Main Features

    • Triggered by tissue damage or infection.

    • Cardinal signs: redness, heat, swelling, pain.

  2. Processes in Inflammation

    • Dilation of blood vessels and migration of leukocytes to affected areas.

  3. Types of Inflammatory Response

    • Acute: Characterized by neutrophils, short-term.

    • Chronic: Long-lasting, with macrophages and granulomas.

Fever

  1. Definition

    • Systemic response regulated by the hypothalamus; raises body temperature to aid immune response.

  2. Pyrogens

    • Agents that induce fever, can be endogenous (body-produced) or exogenous (from pathogens).

  3. Effects of Fever

    • Limits growth of pathogens and enhances host defense mechanisms.

Summary of Key Immune Cells and Their Functions

  1. Cell Types and Characteristics

    • Granulocytes: Neutrophils (55-65%), Eosinophils (2-4%), Basophils (0-1%).

    • Monocytes: Differentiate into macrophages and dendritic cells.

    • Lymphocytes: B cells and T cells (25-35%); crucial for adaptive immunity.

Sensor Systems and Detection of Pathogens

  1. Complement System Overview

    • Proteins circulating in inactive form; activated to assist in pathogen clearance.

  2. Activation Pathways

    • Alternative, lectin, and classical pathways lead to complement activation.

  3. Detection of dsRNA in Viral Infections

    • Long dsRNA indicates viral infection; induces interferon synthesis to prepare neighboring cells for potential infection.

Conclusion

  • The innate immune system forms the crucial first line of defense against pathogens through its barriers, cellular components, and various response mechanisms that work to identify and eliminate threats to the organism.