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Content Inflammatory Response
Physical and Chemical Barriers (Innate Immunity)
Nonspecific Resistance (Innate Immunity)
Specific Resistance (Acquired Immunity)
There are 3 major types of T cells: 1. Cytotoxic T cells
2. Helper T cells
3. Memory T cells
Innate immunity provides broad defenses against infection Present before any exposure to pathogens and is effective from the time of birth Involves nonspecific responses to pathogens A pathogen that successfully breaks through an animal’s external defenses encounters several innate cellular and chemical mechanisms that impede its attack on the body Non-selective and no lag time – immediate response, no previous exposure required Protects against infections, toxins Works with specific (acquired) immune response Physical barriers, secretion, chemical toxins Phagocytosis - macrophages neutrophils engulf and digest recognized "foreign" cells – molecules Inflammatory response - localized tissue response to injury producing swelling, redness, heat, pain Complement system – activated proteins that destroy pathogen plasma membranes Natural Killer cells – special class of lymphocyte-like cells that destroy virus infected cells and cancer cells Interferon - proteins that non-specifically defend against viral infection
Acquired (Adaptive) Immune Response Depends on B and T lymphocytes Specific immune response directed attack against pathogens (antigen) Lag time Previous Antigen exposure required Protects against pathogens and cancer cells Types
Click here for an animation that summarizes the immune response. The animation is followed by practice questions.
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Innate Immunity / External Defenses
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Phagocytes release chemical mediators
- Phagocytes release chemical mediators
Antimicrobial Proteins - Complement System
Adaptive (Acquired) Immune Response - 3rd line of defense Two Components:
Properties of Acquired Immunity |
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Lymphocytes - B and T cells originate in red bone marrow, move to lymphatic tissue from processing sites and continually circulate
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Bone marrow – origin of blood cells Thymus – site of maturing T Lymphocytes Lymph nodes – Exchange Lymphocyte w/ lymph (remove, store, produce, add). Resident macrophages remove microbes and debris from lymph. Lymphocytes produce antibodies and sensitized T cells released in lymph Spleen – Exchange Lymphocytes with blood, residents produce antibodies and sensitized T cells released in blood, (worn RBCs) |
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Antigens
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Cell-Mediated Immunity – T Cells
Major types of T cells Cell-Mediated Immunity – T Cells Antigen Recognition Major Histocompatibility Complex
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Class I MCH molecules are found on almost all nucleated cells of the body display peptide antigens to cytotoxic T cells. Click here for an animation on cytotoxic T cells. The animation is followed by practice questions. For even more practice questions on cytotoxic T cells, click here. |
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Class II MHC molecules are located mainly on dendritic cells, macrophages, and B cells display antigens to helper T cells. | |
1. A fragment of foreign protein (antigen) inside the cell associates with an MHC molecule and is transported
- Macrophages & Dendritic Cells engulf foreign antigens by phagocytosis, proteins broken down into peptides
T Cells Only Recognize Antigen Associated with MHC Molecules on Cell Surfaces
T Helper (TH) Cells
Cytotoxic T (Tc) Cells: Destroy target cells Memory T-Cells - Can survive a long time and give lifelong immunity from infection
Antibody-Mediated (Humoral) Immunity |
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- 1000s of different B cells, each recognizes a different antigen on the surface of a macrophage.
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- Antibodies or Immunoglobulins (Ig) - Classes: IgG, IgM, IgA, IgE, IgD - Structure: Antibodies (immunoglobulins, Ig) are proteins that recognize specific antigens and bind to them. They are found in extracellular fluids (blood plasma, lymph, mucus, etc.) and the surface of B cells. Defense against bacteria, bacterial toxins, and viruses that circulate freely in body fluids, before they enter cells. Antigenic determinants - specific regions of a given antigen recognized by a lymphocyte Antibodies affinity: A measure of binding strength. Consequences of Antibody Binding Antigen-Specific Responses Classes of Immunoglobulins IgM IgA IgD IgE B Cell Antibody Production
Immunological Memory: Secondary Response - Subsequent exposure to the same antigen displays a faster/more intense response due to the existence of memory cells, which rapidly produce plasma cells upon antigen stimulation
Clonal Selection: ...B cells (and T cells) that encounter stimulating antigen will proliferate into a large group of cells. Apoptosis- programmed cell death (“Falling away”). - Human body makes 100 million lymphocytes every day. If an equivalent number doesn’t die, will develop leukemia. Autoimmune Diseases: Failure of “Self-Tolerance” - Some diabetes mellitus – attack beta cells
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Allergic Response - Inflammation Reaction to Non-pathogen - First exposure: sensitization and activation clone B cells that form antibodies and memory cells |
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- Autoimmune diseases are a failure of self-tolerance |
This material is based upon work supported by the Nursing, Allied Health and Other Health-related Educational Grant Program, a grant program funded with proceeds of the State’s Tobacco Lawsuit Settlement and administered by the Texas Higher Education Coordinating Board. |