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Lecture 14

Lecture 14. Immunology: Adaptive Immunity. Principles of Immunity. Naturally Acquired Immunity- happens through normal events Artificially Acquired Immunity- by immunization Active Immunity- result of an immune response in an individual exposed to antigen

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Lecture 14

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  1. Lecture 14 Immunology: Adaptive Immunity

  2. Principles of Immunity • Naturally Acquired Immunity- happens through normal events • Artificially Acquired Immunity- by immunization • Active Immunity- result of an immune response in an individual exposed to antigen • Passive Immunity- occurs naturally during pregnancy; or antibodies from one person transferred to another • Innate Immunity- Immunity that we are born with

  3. Figure 17.1

  4. Adaptive Immunity • Different from Innate Immunity • Matures throughout life • Develops specific immune response as invaders are encountered • Has a “memory” • Must discriminate between self and dangerous (non-self) • Very complex system

  5. Adaptive Immunity • Four important attributes: • Specificity- immune system responds specifically to epitopes • Tolerance of “self”- Immune system does not respond to “self” • Minimal “self” damage- do not damage “self” • Immunologic Memory- Once exposed will not get sick with same disease again

  6. Overview of Adaptive Immunity • Uses two basic strategies • Humoral Immunity - works to eliminate antigens that are extracellular • Cellular Immunity - deals with antigens within host cell

  7. Humoral Immunity

  8. Overview of Humoral Immune Response • Mediated by B-lymphocytes or B-cells • Encounter antigen- differentiate and proliferate into plasma cells and memory B cells • Plasma cells make Y-shaped molecules called antibodies • Antibodies bind to antigens, providing protection to host

  9. Antibodies • Globulin protein molecules- also called Immunoglobulins • Secreted by B-cells • Y-shaped • 5 different classes: • IgM, IgG, IgA, IgE, IgD

  10. Figure 17.3 - Overview

  11. Table 17.1

  12. Immunoglobulin M (IgM) • First class produced during primary immune response to antigen • It is in pentamer form • Large- does not cross from blood to tissues

  13. Immunoglobulin G (IgG) • 80-85% of total Ig’s in people over age 2 • Provides longest term protection of all antibodies • First and most abundant Ig, during secondary response • Can cross placenta from mother to fetus- helps to protect fetus and new-born • Also present in colostrum- first breast-milk produced

  14. Immunoglobulin A (IgA) • Important in mucosal immunity • In breast milk- protects infants from intestinal pathogens Immunoglobulin D (IgD) • Accounts for less than 1% of Ig’s • Involved in development and maturation of antibody response

  15. Immunoglobulin E (IgE) • Barely detectible in blood • Bound tightly to basophils and mast cells • Bound IgE, allows these cells to detect and respond to antigens • These cells release histamine, cytokines, and other chemicals that contribute to immune response

  16. Allergies • Basophils and mast cells release their chemicals when IgE binds to normally harmless material such as pollens • Leads to immediate reaction- coughing, sneezing, and muscular contractions • Response can be life threatening

  17. Primary and Secondary Responses of Antibodies

  18. Protective Outcomes of Antibody-Antigen binding A. Viral Inhibition: virus preventing it from attaching to cell B. Neutralization: make toxins unable to bind to cells C. Opsonization: antibodies bind to antigen and facilitate attachment of phagocytic cells

  19. D. and E. Agglutination and Precipitation: antibodies bind to antigen and get them into clumps, then one big “mouthful” for phagocyte F. Phagocytosis: Fc portion of antibody encourages phagocytosis Complement Activation: binding of antigen to antibody can trigger one pathway of complement cascade

  20. B-cells and Antibody Response • B-cell receptor binds to antigen • One of two things happen: • B-cell needs confirmation by T-cell to begin responding • B-cell does not need confirmation by T-cell to begin responding

  21. When B-cell does not need confirmation from T-cell • B-cell receptors bind epitopes • B-cells respond by proliferating, producing antibody and differentiating into memory B-cells

  22. Fi When B-cell needs confirmation from T-cell gure 16.9

  23. Cellular Immunity

  24. Overview of Cellular Immunity • Mediated by T lymphocytes or T-cells • Has receptor similar to B-cells • Antigen must be presented to it by another cell • Two types: • T-cytotoxic cells- destroy infected cells • T-helper cells- activate macrophages

  25. T-cells: Antigen Recognition and Response • Have multiple copies of receptor on surface that recognizes specific antigen • DO NOT produce antibody • DOES NOT interact with free antigen • Antigen must be presented by another cell, by MHC • Two types of T-cells: • T-cytotoxic • T-helper

  26. Figure 16.15

  27. T-cytotoxic cells • Also called CD8 T cells • Once activated, induce apoptosis in “self” cells infected with virus; destroy cancerous host cells • Distinguish infected “self” cells, because these cells present peptides on surface in MHC class I molecule

  28. Figure 17.10 - Overview

  29. T-helper cells • Also called CD4 T-cells • Antigen presenting cells, present antigen to T-helper cells in MHC class II • If recognize antigen presented as foreign, activate macrophages, release cytokines that recruit other cells of immune system, stimulate NK cells, activate B cells

  30. Figure 17.9 - Overview (1 of 4)

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