1. Chapter 17 Specific Immunity
- Thirdline of Defense
Lymphocytes
- B cells
- T cells
Other cells
Macrophages
Dendritic Cells
Eosinophils -

2. Thirdline of Defense
Specific immunity -- a complex interaction of immune cells (leukocytes) reacting against antigens
Specific – each response is specific for the pathogen that provoked the response
Self and nonself (foreign) – the immune system must be able to tell the difference between foreign vs. self tissues, cells, etc.
Antigens – activate the immune system
Antibodies – made in response to a foreign antigen
specialized lymphocytes - carry out the functions of the immune system

3. Self and nonself “self” Markers
Proteins located on the surface of our cells
Identify your cells as belonging to you
Eg. Major histocompatibility complex (MHC) proteins
Found on all the cells of our body EXCEPT RBCs

4. Markers Lymphocytes recognize the host cell markers as “self”
Tolerance -- Your immune system should not respond against “self” cells & tissues
Autoimmune disease – when your immune system attacks your own tissues
Rheumatoid arthritis, Type I diabetes, lupus
Lymphocytes will recognize microbe proteins as ‘nonself’
Your immune system SHOULD respond against “foreign cells & tissues

5. Specific Acquired Immunities
Active vs. Passive
Active – you make the response
Passive – you receive immune products made by someone else
Natural vs. Artificial
Natural – acquired by natural biological processes
Artificial- acquired by medical process
E.g., Vaccines

6. Active Foreign Antigen activates B and T cells
You make a protective immune response
Memory cells – provide long-term protection
Acquired by
Natural ( you get the infection)
Artificial processes ( vaccine )

7. Passive
You receive pre-formed antibodies from another individual or animal
Short term protection
No memory cells
You don’t produce the antibodies
Natural or artificial

8. Natural
Immunity produced by normal biological experiences, no medical intervention
Natural active
Eg. Infection
Natural passive
Eg. Mother to child – across the placenta, via breast milk

9. Artificial
Immune protection through medical procedures or intervention
Artificial active
Eg. vaccination
Artificial passive
Eg. Injection of preformed antibodies (antiserum)
Immediate but short-lived protection

10. Summary of the different acquired immunities.
Fig Categories of acquired immunities

11. Two Arms of the Immune System
Humoral Immunity
B-lymphocytes produce antibodies
Antibodies in fluids ( blood, lymph, etc.)
Defense against
Bacteria
Toxins
Circulating viruses

12. Two Arms of the Immune System
Cell-Mediated Immunity
T-cells (lymphocytes)
Acts against foreign tissues or organisms
Regulates the activity of other immune system cells

13. Cell-Mediated Immunity
Defends against
Bacteria or viruses that are within the host cells
Fungi, protozoa and helminths
Transplanted tissue
cancer

14. B& T cells are produced in the bone marrow
B& T cells are produced in the bone marrow. Mature T and B cells migrate to the lymphoid tissue, where they encounter antigens.

15. B & T Lymphocytes B&T lymphocytes develop in bone marrow
B-cells remain in bone marrow until mature
T-cells leave bone marrow at immature stage; complete their development in the thymus
Once mature – these cells are released into the lymphatic tissues ( e.g. spleen, tonsils, appendix, gut) or lymph nodes

16. Stages If foreign antigens are present
B and T lymphocytes recognize antigens
B cells become plasma cells - Produce antibodies
T lymphocyte responses
Helper T-cells ( CD4 cells) make chemical messengers called cytokines which help all the cells of the immune system
Cytotoxic T-cells (CD8 cells) seek out & destroy your own infected or abnormal cells

17. An overview of the stages of lymphocyte development and function.
Fig Overview of the stages of lymphocyte development

18. Receptors
Mature B and T cells have very specific receptors on their surface that can specific foreign antigens
B cell receptors can also be secreted as antibodies
These receptors are proteins called immunoglobulins

19. Antigens
Foreign material that is recognized by the immune system and activates the immune response
Size and shape are important

20. Examples of Antigens Microbial products Non-microbial products
Capsules, cell walls
Flagella
Fimbria
Bacterial toxins
Viral protein coats
Other surface molecules
Non-microbial products
Pollen
Egg white
Blood cell surface markers
Serum proteins from other individuals
Transplanted tissues

21. What makes a good antigen? l
Antigenic
Proteins and polypeptides
enzymes, cell surface structures, hormones, toxins
Glycoproteins - blood cell markers
Large Polysaccharides - capsules, LPS on gram negative cell wall)
Not very Antigenic
Lipids & cell membranes
Nucleic acids (DNA)

22. Size and shape
Size affects whether a foreign molecule can act as a good antigen
Too small – no immune recognition
Large – immune recognition
Proteins are better antigens than polysaccharides because of their complex shape

23. Examples of different antigens and their characteristics.
Fig Characteristics of antigens.

24. Antibody Product of B cell activation Structure
Immunoglobulin (Ig) family of proteins
Produced in response to an antigen
Structure
Highly specific for the antigen that stimulated the production of the antibody
Antigen –binding site on the antibody specifically binds the antigen
Has at least two antigen-binding sites

25. Antibody Structure Typical Y-shaped structure
2 identical heavy chains
2 identical light chains
linked to each other
Variable region binds antigen
Constant region
determines the class of the antibody
Also allows antibody to be attached to the surface of a cell.

26. The complete structure of an IgG antibody.
Fig Working models of antibody structure.

27. V-region Variable region
Binds to the antigen
On every antibody the variable region is specific for only one antigen
The antigen & the V region on the antibody must have very specific matching shapes in order to bind

28. FC OR “CONSTANT” REGION
allows the antibody to bind to surface of some cells
E.G., can bind to macrophages
Can also anchors the antibody to lymphocytes or other cells like basophils or eosinophils
Also determines the class of the antibody

29. 5 Classes based on the structure of the constant region
Immunoglobulin (Ig)
IgG
IgA
IgM
IgD
IgE

30. IgM Five Y shaped units – joined by a protein chain ( Very Large)
First to be synthesized during initial immune response
Circulates in the blood, but too big to cross into tissues or across the placenta
The antibody produced in response to your ABO blood type

31. IgG Single Y-shaped Monomer Most common antibody in blood
Small enough to cross the placenta
Primary response –will be produced later in the initial response than IgM
After about 10 days you start making less IgM and more IgG
Memory cell response – strong memory response – these are the long term antibodies you continue to make after you recover from an infection or receive a vaccine

32. IgA
Monomer (single Y )
Dimer – 2 Y shaped monomers, held together by a protein chain (secretory IgA)
Most abundant antibody in the body
Secretory IgA (found in most mucous and serous secretions)
Salivary glands, intestine, nasal membrane, breast, lung, genitourinary tract
Protection for newborns

33. IgD
Single Y – shape
Important in B & T cell maturation

34. IgE
Made in response to
Allergies
Parasite infections
The FC portion binds to mast cells and basophils
Causes them to release chemicals that aid inflammation, allergic response, destroy parasites

35. The characteristics of the different immunoglobulin classes.
Table 15.2 Characteristics of the immunoglobulin classes.

36. B cells Activation Cell Division Antibody production
Antibody-antigen interaction
Response

37. Activation Specific B-cell finds & binds to the matching antigen
B cell divides making multiple copies (clones)
Some change into plasma cells and secrete antibody
Some form memory cells for future protection
Usually also requires chemicals called cytokines produced by T helper lymphocytes that have also recognized the foreign antigen mediators

38. The clonal selection theory of lymphocyte development and diversity.
Fig Overview of the clonal selection theory of lymphocyte
development and diversity.

39. The stages of B-cell activation and antibody synthesis.
Fig Events in B-cell activation and antibody synthesis.

40. Antibody-antigen interactions
Opsonization
Agglutination
Neutralization
Activation of the Complement system

41. The different functions of antibodies.
Fig Summary of antibody functions

42. Agglutination Antibodies cross-link cells or particles into clumps
Renders microbes immobile
Enhances phagocytosis
Principle for certain immune tests (RBC typing)

43. Opsonization Microbes or particles coated with antibodies
Enables macrophages to recognize and phagocytize microbe more efficiently

44. Neutralization Antibody binds to
The microbe, virus or toxin surface
Prevents any further binding of microbe or toxin to your cells

45. Complement fixation
Antibodies interaction with protective complement proteins ( these are made in the liver or by WBCs and circulate in the blood)
Actived complement proteins lyse the microbial cells.

46. Response
Primary
Secondary

47. Primary Response First exposure Latent period Synthesis of antibodies
Lag time until antibodies synthesis begins
Synthesis of antibodies
Level of antibody made is called the titer
IgM first
After about 7-10 days, less IgM made and switch is to mostly IgG

48. Secondary Response
Re-exposure to the same antigen produces a Memory response
Primarily due to memory cells
Antibody synthesis is rapid ( no latent period)
Stronger response ( titer is higher)
IgG dominates

49. The stages of primary and secondary responses to antigens.
Fig Primary and secondary responses to antigens.

50. Cell mediated immunity
Activation
Antigen presenting cells
T cells recognize antigen
Cytokines
Helper T cells
Cytotoxic T cells

51. Cell-mediated immunity
Direct involvement of T cells
Produce and react to cytokines
Activated simultaneously with B cell activation

52. Cell-mediated immunity
Cytokines - Chemical signals produced by
T-cells that have recognized foreign antigen
Activated macrophages
Ex. Interleukins, interferons, Tumor Necrosis Factor ( TNF)
Stimulate or assist most cells involved in the immune response

53. Antigen presenting cells (APC)
Like B cells, each T cell has a receptor that can recognize only one foreign antigen.
They also have receptors called CD proteins.
T-cells only recognize the foreign antigen if it is presented to them on the surface of one of your own cells
Macrophages, dendritic cells act as Antigen Presenting Cells

54. T-cell Activation Activated T-cells begin mitosis and replicate
Macrophages, dendritic cells
Ingest or trap the foreign antigen and now show it on their surface, next to their MHC proteins.
Activated T-cells begin mitosis and replicate
Active cells ( TH and TC ) are produced to act now
Memory cells are also produced for future protection

55. Types
Helper T cells (TH)
Cytotoxic T cells (TC)

56. T Helper cells - TH Have CD4 receptor
Regulate immune by releasing cytokines
Type of cytokine will direct & determine the immune response
activate other T cells
allergic reactions
drive B cell differentiation
also activate macrophages

57. Cytotoxic T cells (TC) Have CD8 receptor on surface
Binds to and lyses cells
microbe, viral infected cells, foreign cells, cancer cells
Perforins – enzymes that punch holes in the membrane of the target cell
Granzymes – degrade proteins
Natural killer (NK) cells
related to TC
attack virus infected cells and cancer cells but are not specific for any one foreign antigen

58. An example of helper and cytotoxic T cell activation and differentiation.
Fig Overall scheme of T-cell activation and
differentiation into different types of T cells.

59. An example of a cytotoxic T cell destroying a cancer cell.
Fig A cytotoxic T cell has mounted a successful
attack on a tumor cell.