The Adaptive Immune Response “Match me perfectly and I’m neutralized”

1. The Adaptive Immune Response“Match me perfectly and I’m neutralized” Kathy Huschle Northland Community and Technical College

2. Adaptive Immune Response • in contrast to the innate immune response which we are basically born with, the adaptive immune response is an ever developing system • it continues to mature throughout our life

3. Adaptive Immune Response • in most cases as each new microbial invader is encountered, our adaptive immune response initiates a specific attack against the invader • generally this invader is remembered and that “memory” is readily available in the case of a second or subsequent attack from the same invader

4. Adaptive Immune Response • this system is an extremely complex system to which we will attempt to gain a basic understand • immunologists are continually discovering many facts about the adaptive immune response

5. Adaptive Immune Response • the adaptive immune response • is learned or acquired • recognizes specific substances foreign to the body • is essential for life

6. Adaptive Immune Response • other terms used for the adaptive immune response include • acquired immunity • specific immunity • though at one time thought to function exclusive of the innate immune system, research is now discovering a correlation between the two systems • regardless of a correlation or not, the failure of our immune system results in mortality

7. Adaptive Immune Response • adaptive immune response is characterized by • specificity • memory • learned ability to recognize (acquired) pathogens which allows the body to usually only suffer once from that particular pathogen

8. Components of the Adaptive Immune System • antigens • antibodies • lymph system • lymphocytes • B cells • T cells • NK cell (Natural Killer) Antigen Antibody B cell T cell NK cell

9. Antigens • the term antigen derives from the two words antibody generator • most antigens are proteins or large polysaccharides

10. Antigens • often a component of invading microbes, such as the capsule, cell wall, flagella, toxin • particular chemical that will activate the adaptive immune response Antigens found in autologous tumor

11. Antigens • invading microbes can have many antigens on its surface pathogen

12. Antigens • when and antigen elicits an immune response it is often referred to as a immunogen • epitope is the reactive portion of the antigen that reacts chemically with an antibody to form the antigen-antibody complex or immune complex

13. Antigens • two essential properties of antigens include • immunogenicity • the ability to stimulate immune system antigen-antibody complex

14. Antigens • specific reactivity • the ability to react with effector molecules (antibody) to form an antigen-antibody complex Antigens in red with green borders

15. Antibodies • glycoproteins that are also referred to as immunoglobiulins • basic structure is a Y shaped molecule with 2 functional parts • Fab region • Fc region Fab region Fc region

16. Antibodies • Fab region • this is the part of the antibody that binds to the antigen • Fc region • the stem of the antibody that functions as a “red flag” • notifies the rest of the immune system: “here I am, come and help”

17. Fab regions The Fab portion of IgG binds to epitopes of a capsule. The Fc portion can now attach the capsule to Fc receptors on phagocytes for enhanced attachment. Once attached to the phagocyte by way of IgG, the encapsulated bacterium can be engulfed more efficiently and placed in a phagosome

18. Antibodies • protection gained from the formation of antigen-antibody complexes basically comes down to the tagging of foreign cells and molecules for destruction by phagocytes and complement Antibodies shown in different stains

19. Antibodies • the antibody molecule is not damaging to the antigen Melanoma antigens

20. Antibodies • foreign organisms and toxins are rendered harmless by • neutralization • immobilization and prevention of adherence • agglutination and precipitation • opsonization • complement activation • antibody-dependent cellular cytosis (ADCC) Respiratory syncytial virus antigens

21. Antibodies • neutralization • blocks the adhesion of bacteria and viruses by bathing the surface of the cell with antibody • immobilization and prevention of adherence • antibodies binding to structures such as flagella and pili can interfere with mobility and attachment

22. Antibodies • agglutination and precipitation • enhances phagocytosis by gathering antigens into clumps • opsonization • coating an antigen with antibody enhances phagocytosis

23. Antibodies • complement activation • enhances cell destruction by cell lysis • antibody-dependent cellular cytotxicity • antibodies attach to target cells causing destruction by non-specific immune system cells

24. Antibodies

25. Antibodies

26. Antibodies • there are 5 classes of immunoglobulins • each class plays a different role in the immune response • IgG • IgM • IgA • IgD • IgE

27. Antibodies • IgG • enhances phagocytosis • neutralizes toxins and viruses • protects the fetus and newborn • only immunoglobulin that is transferred across the placenta

28. Antibodies • IgG • circulates in the blood, but can easily exit to the tissues • most abundant circulating antibody IgG circulating in tissue

29. IgG IgG reacts with epitopes on the host cell membrane. Phagocytes then bind to the Fc portion of the IgG and discharge their lysosomes.

30. Antibodies • IgA • provides localized protection on mucosal surfaces • found in mucus, tears, saliva, sweat, blood, human milk • protects surface tissues and prevents adherence of microorganisms • this is important in respiratory, gastrointestinal and genitourinary tract infections

31. Antibodies • IgM • especially effective against microorganisms and clumping antigens • these are the first antibodies produced in response to a mild infection • are circulating antibodies found in the circulatory system with IgG

32. IgM IgG or IgM reacts with epitopes on the host cell membrane and activates the classical complement pathway. Membrane attack complex (MAC) then causes lysis of the cell.

33. Antibodies • IgD • function of these antibodies is not yet fully defined • it’s presence on B cells functions in the initiation of an immune response

34. Antibodies • IgE • antibodies responsible for allergic reaction • possibly involved in the lysis of parasitic worms • found in the blood serum • plays a role in the initiation of the inflammatory response

35. Lymphoid System • in regards to the immune system the lymphatic system consists of tissues and organs that are designed and located to convey the B and T cells into contact with all antigens that enter the body

36. Lymphoid System • this process is accomplished with the • lymphatic vessels • fluid of the lymphoid system called lymph • secondary lymph organs such as tonsils, spleen, lymph nodes

37. Lymphoid System • primary lymph organs • bone marrow: the location of stem cells that will eventually become B and T cells, B cells mature in the bone marrow • thymus: maturation of the T cells Lymph node Bone marrow with leukemia Healthy bone marrow

38. Lymphoid System • notice how completely our body is covered by the lymphoid system

39. Lymphocytes • critical part of immune system responsible for • detection of foreign antigens • activate immune system • B lymphocytes • T lymphocytes • natural killer cells (NK cells)

40. B lymphocytes: B cells • antibody producing cells that respond to an antigen stimulation • develop from stem cells located in the red bone marrow of adults and the liver of a fetus B Cells dividing

41. B lymphocytes: B cells • following maturation, they migrate to the lymphatic tissue B cell in lymph node

42. B lymphocytes: B cells • once in place in the lymphoid organs, the B cells recognize antigens by means of the antigen receptors found on their cell surfaces • basis for antibody-mediated immunity HIV antigens in yellow B cells in red B indicates a B cell

43. B cells

44. T lymphocytes: T cells • key cellular component of immunity • develop from stem cells found in the bone marrow • precursors to T cells migrate to the thymus, where they reach maturity human T cells

45. T lymphocytes: T cells • following maturity, T cells migrate to various lymph organs where they await contact with antigens • basis for cell-mediated immunity T cells (on left – orange, on right – gray) killing cancer cells (on left- mauve. on right – red)

46. T cells

47. Natural Killer Cells • these cells are not immunologically specific • they do not need to be stimulated by an antigen

48. Natural Killer Cells • capable of destroying other cells, particularly viruses-infected cells and tumor cells • also can attack large parasites

49. Clonal Selection of Lymphocytes • speaks to the ability of B cells and T cells to differentiate to a population of cells capable of recognizing an infinite number of antigens • it is estimated that the human body has approximately 1 billion B cells, yet each individual cell is only capable of recognizing and responding to one antigen B cell differentiation

50. Clonal Selection of Lymphocytes • terms used to define various stages of clonal selection include • immature • naïve • activated • effector • memory