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Immune Response

Immune Response. Vocabulary. Immunology - the study of host defense mechanisms Immunity - ability of the host to protect itself against foreign organisms. Resistance to disease. Antigen (Ag)- is a foreign substance that can elicit specific immune response (IR) when is immunogenic

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Immune Response

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  1. Immune Response

  2. Vocabulary • Immunology- the study of host defense mechanisms • Immunity- ability of the host to protect itself against foreign organisms. Resistance to disease. • Antigen (Ag)- is a foreign substance that can elicit specific immune response (IR) when is immunogenic • Antibody (Ab)- protein produced by the body’s immune system when it detects harmful substances called antigens • White blood cells (leukocytes)- chief function is to protect the body against microorganisms causing disease and fight infection when it occurs. They are bigger than red blood cells.

  3. White Blood Cells (WBC) • 5 Major types of WBC • Neutrophils • Eosonophils • Basophils • Lymphocytes (T and B Cells) • Monocytes • Divided into two categories • Granuolocytes and Agranuolocytes

  4. Granuolocytes • Neutrophils • are the most common WBC in peripheral blood. • Circulate in blood 7-10 hrs before migrating into tissue • Live only a few days • “front line of innate defense” • Increased # used as an indicator of infection • Extravasate in inflammation rxn • Active phagocytes

  5. Granuolocytes • Eosonophils • Function in phagocytosis • Account for less than 5% of WBC • Increased # often present in patients with parasitic infections or allergies • Basophils • Rarest WBC in blood • Non phagocytic • Function as “sirens” for inflammation and allergy

  6. Agranuolocytes • Lymphocytes • Cornerstone of the immune system • Much smaller than the 3 granuolocytes • Help provide a specific response to attack the invading organisms • Are formed in lymphatic tissue throughout the body • Two types of lymphocytes • T cells and B cells, which differ in function and the molecules that are on their surface also differs

  7. Agranuolocytes • Lymphocytes • T cells • Circulate through they thymus gland and have turned into cells known as thymocytes • When exposed to antigens, they rapidly divide and produce large number of new T cells that are sensitive to that type of antigen • More than 80% of lymphocytes circulating in the body are T cells • Divided into 2 main groups • “killer cells” because they produce chemical substances that are essential in helping the B cells destroy foreign substances • Helper T cells which assist the “killer cells” in performing their activities and help protect the body against diseases in other ways

  8. Agranuolocytes • Lymphocytes • B cells • Circulate in the blood in an immature way • About 10% that circulate the blood are B cells • Produce proteins known as antibodies • Antibodies attach to foreign pathogens in the body known as antigens that are found on the surface of certain microorganisms • When B cells divide they produce an identical copies of antibodies on their surface

  9. Agranuolocytes • Monocytes • Largest WBC found in the blood • Originate in the bone marrow • Play important role in the inflammatory response • Present pieces of pathogens to T cells so that pathogens may be recognized and killed • Leave the blood stream to become macrophages • As a monocyte or macrophage, these cells are phagocytic (engulfing) and defend the body against viruses and bacteria

  10. The Immune System • The immune system is a group of cells & soluble molecules, which interact & distinguish patterns in the body as “self” or “non-self,” in order to eliminate those that are “non-self.” • “Non-self” entities include: • Microorganisms, transplants, tumors, foreign substances (eg: asbestos, particulate matter)

  11. The Immune Response • Natural or Innate Immunity (IIR) • Non-specific • Acquired or Adaptive Immunity (AIR) • Specific

  12. The Immune Response • To achieve its duty, the immune system has developed two mechanisms: innate immune response (IIR) & adaptive immune response (AIR). Together, these two systems provide an efficient defense system • It makes it possible that although we spend our lives surrounded by germs, we sporadically get sick. • Most infections are fixed successfully by IIR, other that IIR can not resolve, AIR is triggered and overcome successfully, followed by lasting immunological memory

  13. Innate Immune Response (IIR) • Is the first line of defense in the Immune response • Crucial to control of microorganisms growing freely during early stage of IR • Lacks memory • It is not antigen (Ag) specific • There are a limited recognition molecules • Leads to the AIR

  14. IIR: External Barriers • First line of defense against pathogenic “invaders” • Skin • Largest organ in the body • Produce lactic (low pH) & fatty acids, sweat, skin oils, which make it difficult for microorganisms (MO’s) to survive • When skin is injured, protects the body by way of inflammation • Mucus • Mucosal membranes (mb) lining inner surfaces of the body secrete mucus, which function as protective carbohydrate layer to stop bacterial invasion • Also traps and removes bacteria & particulate matter, by complementary action of cilliary movement, sneezing, coughing • Body secretions • Washing actions of tears, saliva, and urine removes bacteria and foreign particles from the body

  15. Natural or Innate Immunity: Inflammation • When pathogenic agents penetrate external barriers, the first reaction of the body is the inflammatory response • Any time the cells or tissues of the body are injured, internally or on the surface, by whatever agent, the inflammatory response occurs • Acute Inflammatory Response (AIR)- occurs in blood vessels near injury • AIR helps leukocytes to leave the blood vessel (diapedesisor emigration) & travel to injury site via chemotaxis

  16. Acute Inflammatory Response • Chemotaxis- is the movement of cells in response to a chemical attractant • In the inflammatory response, chemicals called mediators, lure the leukocytes to the inflammatory site, where they release enzymes and begin the process of phagocytosis (engulfing and destroying foreign particles or organisms) • Histamine was the first chemical identified as a mediator of the inflammatory response • Interferon- if the cell injury is due to viral infections, interferon, a protein that protects the body against viral infections is released

  17. Acute Inflammatory Response • Complement- a complex of interrelated and interacting proteins manufactured in the liver • Active in inflammation and phagocytosis and also assists the action of antibodies in the specific response in the infecting agent is not destroyed by the nonspecific defenses

  18. Phagocytosis

  19. Adaptive or Acquired Immune Response • Everyone is born with natural immunity to disease, but we can also acquire immunity to disease • Acquired immunity can be acquired naturally or artificially, and it can be active or passive

  20. Acquired or Adaptive Immune Response • Refers to antigen specific defense mechanisms that take several days to become protective and are designed to react with and remove specific antigens • This immunity is developed throughout life

  21. Acquired or Adaptive Immune Response There are two major branches of the adaptive immune response • Humoral • Antibody- mediated immune response • Mediated by B-lymphocytes • Cellular • Cell-mediated immune response • Involves the production of cytotoxic T- lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen • Mediated by T-lymphocytes

  22. Acquired or Adaptive Immune Response • During adaptive immunity: • Bone marrow & thymus (primary lymphoid tissues) produce B cells and T cells, respectively • Immature T cells migrate to thymus and become competent T cells • B cells and T cells recirculate through spleen and lymph nodes (secondary lymphoid tissues) • Antigen (Ag) presenting cells (APC) pick up antigen and migrate to secondary lymphoid tissues & interact with T cells and B cells

  23. Antigen Processing and Presentation • In order to generate adaptive immunity, as well as long lasting memory, Ag should be recognized by T and B cells • Memory usually improves upon repeated exposure to a given infection

  24. Acquired Immunity

  25. Differences in Innate and Adaptive Immunity • The innate and adaptive immune responses both function to protect against invading organisms, but they differ in a number of ways • (1) The innate immune system is constitutively present and reacts immediately to infection. The adaptive immune response to an invading organism takes some time to develop • (2) The innate immune system is not specific in its response and reacts equally well to a variety of organisms, whereas the adaptive immune system is antigen-specific and reacts only with the organism that induced the response • (3) The adaptive immune system exhibits immunological memory. It "remembers" that it has encountered an invading organism (antigen) and reacts more rapidly on subsequent exposure to the same organism. The innate immune system does not possess a memory.

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