Lecture Notes on the Human Immune System

Summary

In this lecture, Danielle explains how the human immune system functions, focusing on its ability to differentiate between self and non-self entities. She discusses the immune system's response to foreign bodies such as bacteria, viruses, and other antigens, detailing the roles and mechanisms of both non-specific (innate) and specific (adaptive) immune responses.

Key Points

Basics of the Immune System

• Differentiation: The immune system identifies and attacks non-self entities known as antigens, which include bacteria, viruses, parasites, fungi, cancer cells, and foreign tissues.
• Outcome: Upon encountering harmful bacteria, the outcome is either death or overcoming the infection through immune response.

Components of the Immune System

• Leukocytes (White Blood Cells): Crucial for combatting infections.
• Actions against pathogens: Isolation, inactivation, and removal of pathogens.

Types of Immune Responses

1. Non-specific Immune Response (Innate Immunity)

   • Reacts to all non-self bodies.
   • Barriers: Skin, saliva, stomach acid.
   • Phagocytic Cells: Macrophages and neutrophils.
   • Chemical Substances: Cytokines (including interleukins and interferons), and the complement system.

2. Specific Immune Response (Adaptive Immunity)

   • Specific to a single type of antigen.
   • Types:
     • Cell-mediated Immunity: Involves T-cells.
     • Humoral Immunity: Involves B-cells producing antibodies.

Inflammatory Response Process

• Trigger: A cut or breach in skin allows bacteria entry.
• Body's Response: Increased blood flow via vasodilation (histamine and bradykinine are involved), which transports more oxygen and nutrients to the inflammation site.
• Symptoms of inflammation: Redness, heat, pain, swelling, and dysfunction of the affected tissue (Rubor, Calor, Dolor, Tumor, Functio Laesia).
• Vascular Permeability: Increases to allow important substances to reach the inflammation site.
• Activation of the Complement System: Attracts leukocytes to inflammation site and aids phagocytes in consuming pathogens.
• Phagocytosis by Neutrophils and Macrophages: Pathogens are ingested and degraded.
• Fever Induction: Caused by IL-1, creates a favorable condition for the body over the bacteria.

Role of T-Cells and B-Cells

• Activation of T-Cells: Specific T-cells multiply and differentiate into cytotoxic T-cells, T-helper cells, memory T-cells, and suppressor T-cells.
• B-Cell Activation: Results in memory cells and plasma cells, which produce antibodies.
• Antibody Types: IgA, IgD, IgE, IgG, IgM, where IgG antibodies are specifically mentioned.
• Antibody Functions: Attach to bacteria marking them for destruction and neutralize toxins released by bacteria.

Conclusion

• The immune system employs a sophisticated set of mechanisms to defeat antigens effectively.
• Upcoming Topic: Overly sensitive immune responses such as allergies and autoimmune diseases.

Closing

Thank you for watching the lecture!

This detailed overview clarifies the formidable complexity and efficiency of the human immune system in protecting the body against various threats.