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The Immune System - General Biology

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  • What are the two main types of immunity in the immune system?
    Innate immunity (nonspecific, immediate defense) and adaptive/acquired immunity (specific, slower response involving B and T cells).
  • What are the primary barrier defenses in innate immunity?
    Skin, mucous membranes, and secretions that kill, inhibit, or trap bacteria (e.g., lysozyme in tears, low pH sweat, mucus in trachea).
  • Name two main types of phagocytes involved in internal innate defenses.
    Neutrophils (most common WBC, ~60%) and monocytes (largest WBC, ~6%) which differentiate into macrophages and dendritic cells.
  • What is diapedesis in the context of neutrophils?
    The process by which neutrophils squeeze through blood vessel walls to enter tissues during immune response.
  • What are PAMPs and how are they recognized?
    Pathogen-associated molecular patterns (PAMPs) are molecules on microbes recognized as non-self by pattern recognition receptors (PRRs) like Toll-like receptors on immune cells.
  • What role do Toll-like receptors (TLRs) play in innate immunity?
    TLRs recognize specific PAMPs, activating phagocytes and triggering release of antimicrobial proteins.
  • Where do macrophages and dendritic cells primarily reside?
    Macrophages reside in lymph nodes, while dendritic cells reside outside the lymphatic system and migrate to lymph nodes after pathogen interaction.
  • How do natural killer (NK) cells function in innate immunity?
    NK cells attack any cell lacking class I MHC by releasing perforins that cause the target cell to lyse.
  • What are the two main types of antimicrobial proteins in innate immunity?
    Complement proteins (circulate inactive, activate to opsonize or lyse cells) and interferons (signal uninfected cells to inhibit viral replication).
  • What is opsonization?
    The process where complement proteins bind to pathogens, marking them for enhanced phagocytosis.
  • Describe the membrane attack complex (MAC).
    A complex formed by complement proteins C5b-C9 that creates pores in microbial membranes, causing cell lysis.
  • What are the cardinal signs of inflammation?
    Heat, swelling, redness, and pain caused by vasodilation and increased capillary permeability.
  • What triggers inflammation?
    Damaged cells release inflammatory chemicals that cause vasodilation, increased capillary permeability, and attract white blood cells.
  • Define antigen in the immune system context.
    A large molecule recognized as non-self by the immune system, capable of triggering an immune response.
  • What are antibodies and their function?
    Proteins produced by B cells that bind to specific antigenic determinants, marking pathogens for destruction.
  • What are the two classes of MHC proteins and where are they found?
    Class I MHC found on almost all body cells; Class II MHC found mainly on antigen-presenting cells like macrophages, dendritic cells, and B cells.
  • What is the role of antigen-presenting cells (APCs)?
    APCs phagocytize invaders, display antigens on MHC II molecules, and activate other immune cells.
  • Outline the steps of the humoral immune response.
    1. B-cell activation by antigen binding and helper T cell co-stimulation. 2. Clonal selection producing plasma cells (antibody secretion) and memory cells.
  • Compare primary and secondary immune responses.
    Primary response occurs after first antigen exposure with antibody peak ~10 days; secondary response is faster and stronger, peaking within 2-3 days.
  • What is the difference between active and passive humoral immunity?
    Active immunity involves antibody production by the host (natural infection or vaccine); passive immunity involves receiving antibodies (breastfeeding or serum injection).
  • How do antibodies neutralize pathogens?
    By binding to antigens, antibodies neutralize pathogens, activate complement, and promote opsonization.
  • What is required for T-cell activation?
    Antigen binding and co-stimulation, often from activated helper T cells releasing cytokines.
  • What is the function of cytotoxic T cells?
    They attack and destroy infected cells presenting specific antigens.
  • What causes immunodeficiencies?
    Abnormal production or function of immune cells or complement, either congenital (e.g., SCID) or acquired (e.g., AIDS).
  • What are autoimmune diseases?
    Conditions where the immune system attacks the body's own tissues, e.g., multiple sclerosis, rheumatoid arthritis, type I diabetes.
  • What is hypersensitivity in immune response?
    An exaggerated immune reaction causing tissue damage, such as allergies involving mast cell histamine release.