Chapter 22 Lecture Notes Flashcards

Introduction to Resistance and Immunity

  • Resistance: Ability to ward off pathogens.
  • Susceptibility: Lack of resistance.
  • Nonspecific resistance (innate immunity): Present at birth, general protection.
  • Immunity: Activation of specific lymphocytes against specific pathogens.
  • Lymphatic system: Carries out immune responses.

Lymphatic System Structure and Function

  • Components: Lymph, lymphatic vessels, lymphatic tissue, bone marrow.
  • Interstitial fluid and lymph are similar, differing mainly in location.
  • Functions: Drains interstitial fluid, returns plasma proteins, transports dietary fats, protects against invasion.

Lymphatic Vessels and Lymph Circulation

  • Lymphatic vessels: Originate as lymph capillaries in tissue spaces.
  • Lymph capillaries: Larger diameter than blood capillaries, one-way valves.
  • Lymph trunks: Lumbar, intestinal, bronchomediastinal, subclavian, jugular.
  • Thoracic duct: Main collecting duct, drains lymph from most of the body into the left subclavian vein.
  • Right lymphatic duct: Drains lymph from the upper right side of the body into the right subclavian vein.
  • Lymph flow: Arteries → blood capillaries → interstitial spaces → lymph capillaries → lymphatic vessels → lymph trunks → thoracic/right lymphatic duct → subclavian veins.

Lymphatic Organs and Tissues

  • Primary lymphatic organs: Red bone marrow (B cell immunocompetence) and thymus gland (T cell immunocompetence).
  • Secondary lymphatic organs/tissues: Lymph nodes, spleen, lymphatic nodules.
  • Thymus gland: T cell maturation, shrinks after puberty.
  • Lymph nodes: Encapsulated structures with T cells, macrophages, B cells; filter lymph.
  • Spleen: Largest lymphatic tissue mass, contains white and red pulp.
    • White pulp: Lymphatic tissue; T cells attack antigens, B cells become plasma cells.
    • Red pulp: Venous sinuses; macrophages remove old blood cells, stores platelets.
  • Lymphatic nodules: Concentrations of lymphatic tissue in mucous membranes (MALT), e.g., Peyer’s patches, tonsils.

Innate Immunity: First and Second Lines of Defense

  • Innate immunity: Nonspecific, present at birth.
  • First line of defense: Skin and mucous membranes provide mechanical and chemical protection.
  • Second line of defense: Internal antimicrobial proteins, phagocytes, NK cells, inflammation, fever.
  • Antimicrobial proteins: Interferons (IFNs), complement system, iron-binding proteins, antimicrobial substances.
  • Natural killer (NK) cells: Kill microbes via perforins.
  • Phagocytosis: Chemotaxis, adherence, ingestion, digestion.
  • Inflammation: Vasodilation, increased permeability, phagocyte migration, tissue repair; characterized by redness, pain, heat, swelling.
  • Fever: Inhibits microbial growth, speeds up body reactions.

Adaptive Immunity

  • Immunity: Defends against specific invading agents.
  • Antigens: Substances recognized as foreign.
  • Specificity and memory are key properties.
  • T cells mature in thymus; B cells in bone marrow.
  • Cell-mediated immunity: T cells destroy antigens.
  • Antibody-mediated (humoral) immunity: Antibodies destroy antigens.
  • Clonal selection: Immune cell proliferation and differentiation in response to antigen. Creates effector and memory cells.
  • Antigens: Recognized by antigen receptors.
  • MHC antigens: Unique to each person; aid in detection of foreign invaders.
  • Antigen Processing Pathways:
    • Exogenous antigens presented by APCs with MHC class II to T cells.
    • Endogenous antigens processed and presented by most cells with MHC class I.
  • Cytokines: Small protein hormones that regulate immune responses.

Cell-Mediated Immunity (CMI)

  • T cells recognize antigen fragments associated with MHC molecules.
  • Helper T (TH) cells (CD4): Recognize antigen fragments with MHC-II, secrete cytokines.
  • Cytotoxic T (TC) cells (CD8): Recognize antigen fragments with MHC-I.
  • Cytotoxic T cells eliminate invaders by cytolysis (perforin) or activating enzymes in target cell (lymphotoxin).
  • Immunological surveillance: Cytotoxic T cells recognize and destroy tumor cells.

Antibody-Mediated Immunity

  • B cells activated when antigen binds to receptors.
  • Helper T cells provide co-stimulation for B cell proliferation.
  • Plasma cells secrete antibodies; memory B cells provide immunological memory.
  • Antibodies: Combine with specific antigenic determinants; classes include IgG, IgA, IgM, IgD, IgE.
  • Antibody actions: Neutralizing antigen, immobilizing bacteria, agglutination, complement activation, enhancing phagocytosis.
  • Monoclonal antibodies: Produced by hybridomas; used in diagnostics and treatment.
  • Complement system: Enhances immune reactions.
  • Immunological memory: Long-lived antibodies and lymphocytes.

Self-Recognition and Tolerance

  • T cells undergo positive and negative selection to ensure self-recognition and tolerance.
  • B cells develop tolerance through deletion and anergy.
  • Cancer immunology: Using the immune system to detect and treat cancer.

Stress and Aging Effects on Immunity

  • Psychoneuroimmunology (PNI): Links nervous, endocrine, and immune systems.
  • Aging: Immune system function declines, increased susceptibility to infections.

Disorders: Homeostatic Imbalances

  • AIDS: Caused by HIV, destroys immune cells, leading to opportunistic infections.
  • Hypersensitivity (allergic reactions): Type I (anaphylaxis), Type II (cytotoxic), Type III (immune complex), Type IV (cell-mediated).
  • Autoimmune diseases: Immune system attacks own tissues.
  • Infectious mononucleosis: Caused by Epstein-Barr virus.
  • Lymphomas: Cancers of lymphatic organs.
  • Systemic lupus erythematosus: Chronic autoimmune disease.