Lecture Notes on Immune System Overview
Summary of the Lecture
In this lecture, Danielle provides an overview of the immune system, focusing on how it identifies and attacks non-self substances like bacteria, viruses, parasites, fungi, cancer cells, and foreign organs. She explains the two main divisions of the immune system—innate (nonspecific) and adaptive (specific)—and details how these components work together to fight off pathogens and protect the body.
Key Points
Introduction to the Immune System
- Distinction Between Self and Non-self: Essential for the immune response.
- Attack Targets: The immune system targets non-self substances (antigens) including bacteria, viruses, fungi, etc.
Components and Functions of the Immune System
- Innate (Aspecific) Immunity:
- Immediate response to all non-self entities.
- Includes physical barriers (skin, saliva, stomach acid).
- Cellular components like macrophages and neutrophils.
- Chemical factors such as cytokines (interleukins, interferons) and the complement system.
- Adaptive (Specific) Immunity:
- Targets specific antigens.
- Works through millions of different lymphocytes prepared for various pathogens.
- Divided into:
- Cell-mediated immunity: Provided by T-cells.
- Humoral immunity: Provided by B-cells.
Response to Infection
- Example Scenario: Skin wound exposing the interior to bacteria.
- Inflammatory Response: Characterized by increased blood flow (vasodilation), redness, heat, pain, swelling (collectively known as rubor, calor, dolor, tumor), and dysfunctional tissue behavior (functio laesia).
- Steps in Cellular Reaction:
- Activation of the Complement System: Attracts leukocytes and enhances phagocytosis.
- Arrival of Neutrophils: Engages in phagocytosis of the invading bacteria.
- Macrophages Assist: They consume bacteria and clean debris.
- Activation of T-cells: A macrophage will present parts of the consumed bacteria to T-cells, which then clone themselves to fight the specific antigen.
- Types of T-cells Produced:
- Cytotoxic T-cells (killer cells)
- Helper T-cells (coordinate defense and activate B-cells)
- Memory T-cells (quick response for future encounters)
- Suppressor T-cells (regulate and prevent overreaction which can harm the body)
- Activation of B-cells: Occurs in lymph nodes; divides into memory cells and plasma cells which produce antibodies.
- Antibody Types Produced: Primarily IgG in this scenario, which tags bacteria for quicker elimination by other immune cells and neutralizes bacterial toxins.
Overview and Future Topics
- The immune system employs a comprehensive strategy to neutralize threats, involving various cells and reactions coordinated for effective defense.
- Next Topic: Over-sensitive immune responses, including allergies and autoimmune diseases.
Thank you for attending the lecture on the immune system!