Immunity22

Immunity and Defense

Page 1: Introduction

• Immunity and Defense Overview

• Basic concepts of immune response

Page 2: Objectives

• Understand major functions, organization, and histological components of the lymphatic system

• Explain mechanisms of innate defenses

• Discuss development and activation of cellular and humoral immunity

Page 3: Immune System & Body’s Defense

• Immune System: Protects from infectious agents and harmful substances

• Usually operates unnoticed

• Involves cellular and molecular structures for immunity

• Function depends on the type of infectious agent

Page 4: Diseases and Infectious Agents

• Infectious agents damage or kill hosts

• Pathogenic agents: cause harm

• Five categories:

  • Bacteria

  • Viruses

  • Fungi

  • Protozoans

  • Multicellular parasites

Page 5: Types of Infectious Agents

• Bacteria: Shapes include spherical (cocci), rod-like (bacilli), coiled (spirilla)

• Harmless vs. virulent bacteria

• Examples of virulent bacteria: Clostridium tetani (tetanus), streptococcal bacteria (strep throat)

Page 6: Viruses

• Obligate intracellular parasites that need host cells to reproduce

• Infect cells to create copies of their nucleic acids and capsids

• Some common infections: cold, Ebola, chickenpox, COVID-19

Page 7: Fungi

• Includes molds, yeasts, multicellular fungi producing spores

• Cause diseases like ringworm and vaginal yeast infections

Page 8: Protozoans

• Eukaryotic cells without a cell wall

• Examples include malaria and trichomoniasis

Page 9: Prions

• Fragments of infectious proteins that cause diseases in nervous tissue

• Example: Variant Creutzfeldt-Jakob disease

Page 10: Immune Cells and Their Locations

• Leukocytes: Formed in red bone marrow

• Types: Granulocytes (neutrophils, eosinophils, basophils), Monocytes (migrate as macrophages), Lymphocytes (B-lymphocytes, T-lymphocytes, NK cells)

Page 11: Cytokines

• Small proteins that regulate immune activity

• Produced by both innate and adaptive immune cells

• Functions include:

  • Signaling immune and non-immune cells

  • Controlling development of immune cells

  • Regulating inflammatory responses

Page 12: Cytokine Categories

• Interleukin (IL): e.g., IL-1, IL-2

• Tumor necrosis factor (TNF): e.g., TNF-α

• Colony-stimulating factor (CSF): e.g., granulocyte CSF

• Interferon (IFN): e.g., INF-α

Page 13: Immunity: Two Intrinsic Defense Systems

• Innate (nonspecific) system:

  • First line: skin and mucosae

  • Second line: antimicrobial proteins, phagocytes,

• Quick response, ready for attack

• Adaptive (specific) defense:

  • Third line: mounts attack against specific foreign substances

  • Takes longer to react but works alongside the innate system

Page 14: Innate and Adaptive Defenses

• Innate Immunity: Immediate and nonspecific response

• Adaptive Immunity: Delayed response to specific antigens through B-cells and T-cells

Page 15: Mechanisms of Innate Immunity

• Physical barriers, chemical barriers, and inflammation as first responses to pathogens

Page 16: Inflammation Response and Its Importance

• Inflammation prevents spread of pathogens and promotes repair

• Four cardinal signs: redness, heat, swelling, pain

Page 17: Clinical View: Pus and Abscesses

• Pus comprises dead leukocytes and pathogens

• Abscess formation when pus is walled off

Page 18: Fever

• Elevated body temperature as a response to pathogens

• Pyrogens reset the body's temperature set point

Page 19: Adaptive Immunity

• Recognizes and responds to specific foreign substances

• Two arms: Humoral (B cells) and cellular (T cells)

Page 20: Activation of B-Lymphocytes

• B-antigen encounter in lymphoid organs leads to clonal selection and antibody production

• Memory B-Lymphocytes facilitate quicker responses upon re-exposure to the antigen

Page 21: Mechanisms of B-cell Activation

• B-cells require two activation signals: antigen binding and help from T-cells

Page 22: Immunoglobulins

• Antibodies (Ig) — five classes: IgD, IgM, IgG, IgA, IgE

• Antibodies function by neutralization, agglutination, and opsonization

Page 23: Cell-mediated Immunity

• Uses T-cells to directly target and destroy infected or abnormal cells

• T-cells undergo positive and negative selection in the thymus to ensure proper function

Page 24: Autoimmune Disorders

• Occurrence when immune system misidentifies self-antigens as foreign

• Examples: Multiple sclerosis, Type 1 diabetes, Rheumatoid arthritis

Page 25: Allergies and Hypersensitivity

• Immune responses that damage tissue; acute and delayed types

• Anaphylaxis and symptoms associated with it may require immediate treatment

Page 26: Summary of Immune Processes

• Immune response involves cooperation between various cells and cytokines

• Key components: T-cells and B-cells, memory cells, and antibodies