Immunity Overview and Responses

Immunity Overview

• Immunity is the body's total defense mechanisms against infection by foreign organisms and molecules.
• It involves various processes to protect the body.

Immune Response Summary

• B cells recognize and bind specific antigens.
• Helper T cells activate B cells.
• Activated B cells produce plasma and memory cells.
• Plasma cells create antibodies targeting specific invaders.
• Phagocytes target antibody-marked invaders.
• Memory cells facilitate a rapid response to subsequent invasions.
• Innate immunity is an individual's inherent resistance to infection.
• Adaptive immunity is a specific body resistance to pathogens.
• The innate immune system provides a rapid response, while the adaptive immune system provides a slower, more specific response.

Immune System Components

• External Defense System: First line of defense, consisting of physical and chemical barriers.
  • Physical barriers include skin and mucous membranes.
  • Chemical barriers include stomach acid, saliva, sweat, tears, and vaginal secretions.
• Internal Defense System: Second line of defense, involving internal components promoting immunity, and inflammation.
  • Components include phagocytic cells (example: neutrophils, monocytes, macrophages, natural killer cells), cytokines, and complement.

Cellular Components

• Granulocytes: (neutrophils, eosinophils, basophils)

• Neutrophils: Principal phagocytic leukocytes involved in localized inflammatory responses.

• These cells are primarily responsible for phagocytosis.

• They respond to a variety of signals, including those from bacteria, injured tissue, and other white blood cells.

• Eosinophils: Phagocytic, involved in killing parasites and inflammatory reactions. They also produce specific proteins.

• Basophils: Involved in hypersensitivity reactions. These cells contain granules that play a role in inflammation.

• Agranulocytes: (monocytes, macrophages, mast cells, dendritic cells)

• Monocytes: Precursors to macrophages, critical for antigen presentation.

• These cells process and present antigens to lymphocytes.

• Monocytes migrate to tissues, becoming macrophages.

• Macrophages: Involved in phagocytosis, antigen presentation, and inflammatory responses. Macrophages are transformed monocytes.

• Mast cells: Involved in hypersensitivity reactions. They have a role in inflammation and response to parasitic infections.

• Dendritic cells: Important antigen-presenting cells, initiating acquired immune responses. Antigen-presenting cells.

• Lymphocytes: (T cells, B cells, natural killer cells)

Humoral Components

• Cytokines: These mediate communication between immune cells.
  • Examples include interferons, interleukins, and tumor necrosis factor.
• Complement: A system of proteins that helps with inflammation, opsonization.
• These proteins act in a cascade-like manner to eliminate pathogens. They are important in mediating inflammation, opsonization and cell lysis.

Other Key Concepts

• Pathogen-Associated Molecular Patterns (PAMPs): Molecule associated with a group of pathogens.
• Pattern Recognition Receptors (PRRs): Receptors on host cells recognize PAMPs and trigger innate immune responses.
• Phagocytosis: The process of engulfing and destroying pathogens.
• Inflammation: The body's reaction to injury or infection, characterized by redness, swelling, heat, and pain.
• Interferons: Proteins produced by infected cells to protect neighbouring cells from viral infection.
• Tumor Necrosis Factor (TNFs): Proteins that kill tumor cells and are involved in inflammation.
• Interleukins (ILs): Cytokines mediating communication between leukocytes; they stimulate inflammation, growth of various blood cells, and immune responses.
• Acute Phase Reactants: These proteins increase in response to injury or infection and are involved in inflammatory processes.
• Immune response: The body's response to an antigen, involving both humoral and cellular mechanisms.
• Antibody production: The creation of antibodies in response to an antigen; it has two main phases: primary and secondary.
• Types of Immunization: Active and passive. Active immunization involves administration of vaccines; passive involves administration of antibodies.
• Cellular Resolution and Repair: These are the processes of resolving the injury.