Glossary for Immunity

Immunity Types & Responses

• Active Immunity: Immunity acquired through exposure to a pathogen, either naturally (infection) or artificially (vaccination), leading to memoryThe ability to store and recall information. cell production.
• Passive Immunity: Temporary immunity acquired by receiving antibodies from another source, such as maternal antibodies or antibody injections.
• Primary Response: The initial immune response to an antigen, characterized by a slower response and lower antibody production.
• Secondary Response: A faster, stronger immune response upon subsequent exposure to the same antigen due to memory cell activation.
• Hypersensitivity: An exaggerated immune response to a harmless antigen, such as allergies or autoimmune diseases.

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Immune Cells & Their Functions

• B Cells: White blood cellsThe basic structural and functional units of life. that mature in the bone marrow and produce antibodies to fight infections.
• T Cells: White blood cells that mature in the thymus and are responsible for cell-mediated immunity.
• CD4 T Cell (Helper T Cell): A type of T cell that coordinates immune responses by activating B cells, T cells, and other immune cells.
• CD8 T Cell (Cytotoxic T Cell): A type of T cell that directly kills infected or abnormal cells.
• Plasma Cells: B cells that have been activated to produce and secrete large amounts of antibodies.
• Natural Killer (NK) Cells: Lymphocytes that kill virus-infected and cancerous cells without prior activation.
• Phagocytes: Cells that engulf and digest pathogens and debris (e.g., macrophages, neutrophils).
• Microphages: Smaller phagocytic cells like neutrophils and eosinophils that attack pathogens.
• Dendritic Cells: Antigen-presenting cells that activate T cells by displaying foreign antigensMolecules on the surface of cells that trigger an immune response..

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Antigens & Antibodies

• Antigens: Foreign substances (proteinsLarge molecules made of amino acids with various functions in the body., polysaccharides) that trigger an immune response.
• Complete Antigens: Molecules that can independently trigger an immune response.
• Haptens: Small moleculesGroups of atoms bonded together. that must bind to a larger protein to become antigenic.
• Antigenic Determinants (Epitopes): The specific part of an antigen that an antibody or immune cell recognizes.
• Antibodies (Immunoglobulins): Proteins produced by B cells that specifically bind to and neutralize antigens.

Immunoglobulin (Antibody) Types

• IgA: Found in mucous membranes (saliva, tears, breast milk); provides mucosal immunity.
• IgE: Involved in allergic reactions and parasite defense.
• IgG: The most abundant antibody in blood; provides long-term immunity and can cross the placentaThe organ that facilitates nutrient and waste exchange between the mother and fetus..
• IgM: The first antibody produced in an infection; effective in forming antigen-antibody complexes.

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Immune System Components & Molecules

• Major Histocompatibility Complex (MHC) Class I: Proteins found on all nucleated cells that present antigens to CD8 T cells.
• Major Histocompatibility Complex (MHC) Class II: Proteins found on antigen-presenting cells that present antigens to CD4 T cells.
• Cytokines: Signaling proteins that regulate immune responses, inflammation, and cell communication.
• Perforin: A protein released by cytotoxic T cells and NK cells that creates holes in target cell membranes, leading to cell death.
• Histamine: A chemical released by mast cells and basophils that increases inflammation and causes allergy symptomsSubjective experiences reported by the patient (e.g., nausea, fatigue)..
• Interferons: Proteins that help cells resist viral infections and activate immune responses.
• Pyrogens: Substances that induce fever by affecting the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions..
• Fever: An immune response that increases body temperature to enhance immune function and inhibit pathogen growthAn increase in size and number of cells..

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Immune System Processes

• Agglutination: Clumping of antigens by antibodies to facilitate pathogen removal.
• Precipitation: Formation of antigen-antibody complexes that settle out of solutionA homogeneous mixture of two or more substances., making pathogens easier to remove.
• Opsonization: Coating of a pathogen with antibodies or complement proteins to enhance phagocytosis.
• Lysis: Destruction of a cell by breaking its membrane, often through complement activation or perforin.
• Degranulation: Release of granules (e.g., histamine, enzymesProteins that speed up chemical reactions in the body.) from immune cells like mast cells and eosinophils.
• Apoptosis: Programmed cell death, a natural process that removes infected or damaged cells.
• Adhesion: The process of immune cells binding to each other or to pathogens.
• Chemotaxis: The movementA fundamental property of life involving motion of the body or its parts. of immune cells toward the site of infection in response to chemical signals.
• Inflammation: The body’s response to injury or infection, characterized by redness, swelling, heat, and pain.

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Immune Disorders & Reactions

• Anaphylactic Shock: A severe allergic reaction causing widespread inflammation, airway constriction, and low blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange..
• Pathogen: Any microorganism (bacteria, virus, fungus, parasite) that can cause disease.