Immunology & Immune System Intro

Overview of the Immune System

• The immune system includes all body parts that recognize and destroy foreign materials, comprising white blood cells, phagocytes, lymphocytes, bone marrow, lymph nodes, tonsils, thymus, and spleen.
• Immunity provides protection against infections via a coordinated immune response involving various cells, tissues, and molecules.

Classification of Immune System Organs

• Primary Lymphoid Organs: Thymus and bone marrow are essential for developing immune cells.
• Secondary Lymphoid Organs: Includes tonsils, lymph nodes, spleen, Peyer’s patches, appendix, and tissue lymphatics where immune responses are initiated.

Types of Immunity

• Innate (Non-Specific) Immunity:

  • First-Line Defenses: Includes physical and chemical barriers like skin, sweat, tears, saliva, mucus, and stomach acid that act as the body’s initial defenses against pathogens.
  • Second-Line Defenses: Involves the inflammatory response characterized by redness, heat, swelling, and pain upon pathogen invasion.

• Adaptive (Specific) Immunity:

  • Involves antigen-specific immune responses, producing specialized cells and antibodies that destroy pathogens, with memory for faster response during re-exposure.

Active vs. Passive Immunity

• Active Immunity: Develops resistance through active engagement of the immune system in response to an antigenic stimulus, involving the production of antibodies over time.
• Passive Immunity: Involves transfer of pre-formed antibodies without engaging the recipient's immune response, offering immediate but temporary protection.

Antigens and Antibodies

• Antigen: Foreign substances that specifically bind to antibodies or T cell receptors, triggering an immune response; common antigens include proteins and polysaccharides.
• Types of Antigens: Autoantigens (self), alloantigens (from other individuals of the same species), and heterophile antigens (identical antigens across different species).
• Antibody (Immunoglobulin): A protein produced by B cells that binds specifically to antigens; classified into IgM, IgG, IgA, IgD, and IgE.

Immune Response Mechanisms

• Humoral Immunity: Involves antibodies secreted by B cells that bind to antigens.
• Cellular Immunity: Mediated by cytotoxic T lymphocytes that destroy infected cells and helper T cells that assist B cells and T cells in responding.

Immunization Strategies

• Passive Immunization: Administration of pre-formed antibodies for immediate protection.
• Active Immunization: Vaccination with microbes or their antigens to induce an immunological response enabling future protection.

Disorders of the Immune System

• Hypersensitivity Reactions: Over-reactions of the adaptive immune response to harmless antigens, categorized into four types.
• Autoimmunity: Misdirected immune response leading to damage of self-tissues due to loss of self-tolerance; consists of three types of reactions.
• Immunodeficiencies: Result from absent or defective components of the immune system, with genetic or acquired causes.

Hypersensitivity Diseases

• Definition: Abnormal immune responses upon re-exposure to previously encountered antigens.
• Types of Hypersensitivity: Identified by their pathogenesis and resulting clinical manifestations; the terminology prefers descriptive terms over numerical classification.

This quiz covers the fundamental concepts of immunology and the immune system. It explores the roles of various components such as white blood cells, phagocytes, and lymphocytes in recognizing and combating foreign materials. Test your knowledge on how the body defends itself against infections.