1. Lymphatic System and Immunity
Chapter 22

2. Lymphatic System Functions: 1. Drain excess interstitial fluid.
2. Transporting dietary lipids
3. Protection against invasion by foreign chemicals
and microorganisms

3. Lymphatic System
Organs
Lymphatic vessels
Lymph

4. Lymphatic Capillaries
Carry lymph from tissue spaces to lymphatic vessels (lymphatics)
Lacteals - capillaries in intestine - digested fat absorbed into lymph
Slightly larger diameter than blood vessels
Interstial fluid flows in but not out

5. Lymph Trunks and Ducts

6. Lymph Forms by filtration Similar to plasma Large number of WBCs
Few platelets
Few RBCs and thrombocytes
Low in protein concentration
Contains little O2

7. Lymphatic vessels and lymph nodes
Lymphatic Circulation
capillaries
Interstitial space
Lymph capillary
arteries
Lymphatic vessels and lymph nodes
heart
Lymph trunk
veins
Lymph duct

8. Lymphatic Circulation

9. Lymphatic Organs Primary organs Secondary Organs/Tissues
Red bone marrow
Thymus
Secondary Organs/Tissues
Lymph nodes
Spleen
Lymphatic nodules

10. Thymus
Behind sternum
one of the central controls of the immunity system
large in fetus and 0-2 yrs
increases in size until adolescence; atrophies
Produces lymphocytes (T-cells) and antibodies

11. Lymph nodes

12. Lymph nodes
Filter lymph
Quarantine noxious products
Phagocytosis

13. Spleen Functions: 1. Blood destruction 2. Blood production
3. Immunologic function
4. Blood storage
5. Blood filtration
6. Phagocytize bacteria and old RBC

14. Lymphatic Nodules
Concentrations of lymphatic tissue not surrounded by a capsule scattered throughout connective tissue of mucous membranes
Peyer’s patches in the ileum of the small intestine
Appendix
Tonsils form ring at top of throat
adenoids (pharyngeal tonsil)
palatine tonsils (on each side wall)
lingual tonsil in the back of the tongue

15. Immune System
Immunity: body’s ability to resist or eliminate potentially harmful foreign materials or abnormal cells
Nonspecific immunity: nonselective protection
Specific immunity: depends upon recognition of substance

16. Nonspecific Defenses (Innate Immunity)
1. Mechanical/Chemical barriers
2. Phagocytic Cells
3. Natural Killer (NK) cells
4. Inflammatory response
5. Complement system and Interferon

17. Mechanical/Chemical Barriers
skin
mucous membrane
lacrimal apparatus
sebum
perspiration
gastric juice

18. Phagocytic cells Macrophages (monocytes) fixed macrophage
free macrophage
Neutrophils

19. Natural Killer (NK) Cells
kill a variety of microbes & tumor cells
found in blood, spleen, lymph nodes & red marrow
attack cells displaying abnormal MHC antigens

20. Inflammatory Response
1. Vasodilation
- capillary permeability increased
2. Phagocytes activated
3. Tissue repair
- clotting reaction walls off region
- regional temperature increased

21. Complement 1. Destruction of bacterial cell walls
2. Inactivation of viruses
3. Stimulation of inflammation
4. Chemical attraction of phagocytes
5. Enhancement of phagocytic activity
Complement

22. Interferon
antiviral chemical produced by an infected host cell

23. Nonspecific Defenses (Innate Immunity)

24. Specific (Adaptive) Immunity
1. Antibody mediated (Humoral immunity): antibody or immunoglobulin production
Cell-mediated immunity:
cells directly attack

25. Clonal selection
Process by which a lymphocyte proliferates and differentiates in response to a specific antigen
Clone – population of identical cells all recognizing the same antigen as original cell
Lymphocyte undergoes clonal selection to produce
Effector cell – active helper T cell, active cytotoxic T cell, plasma cell, die after immune response
Memory cell – do not participate in initial immune response, respond to 2nd invasion by proliferating and differentiating into more effector and memory cells, long life spans

26. Antigens Antigens have 2 characteristics
Immunogenicity – ability to provoke immune response
Reactivity – ability of antigen to react specifically with antibodies it provoked
Entire microbes may act as antigen
Typically, just certain small parts of large antigen molecule triggers response (epitope or antigenic determinant)

27. Major Histocompatibility Complex Antigens
Self Antigens
Major Histocompatibility Complex Antigens
MHC or human leukocyte antigens (HLA)
Normal function to help T cells recognize foreign or self
Class I MHC (MHC-I) – built into all body cells except RBCs
Class II MHC (MHC-II) – only on antigen presenting cells

28. Antigen Processing (Exogenous)

29. Antigen Processing (Endogenous)

30. Chemical Communication
Cytokines
Small protein hormones involved in immune responses
Secreted by lymphocytes and antigen presenting cells

31. Cell-mediated immunity
Formation of specially sensitized lymphocytes that have the capacity to attach to the foreign agent and destroy it.
T cells
helper T cells
cytotoxic T cells
memory T cells

32. Activation of Helper T Cells
CD4 T cells
Release cytokines which activate other immune cells

33. Activation of Cytotoxic T cells
CD8 cells T cells
Attack
- cells infected by microbes
- tumor cells
- transplant tissue

34. Cytotoxic
T Cell
In action

35. Memory T Cells
Available for swift response if a 2nd exposure to same foreign antigen should occur

36. Antibody-mediated immunity
Humoral Immunity
Antibody-mediated immunity
antigen
B Cell
Plasma Cell
Memory Cell
Primary response
Secondary response
antibodies
Plasma Cell

37. Activation of B Cells

38. Antibodies Immunoglobulins
produced by plasma cells in response to an antigen
Molecule consists of two parallel pairs of polypeptide chains
Fixed segment - same for all antibodies in the same class and is responsible for type of antigen-antibody reaction
Variable segment - antigen binding site; accounts for specificity

39. Antibody Structure

40. Antibody Diversity Immunoglobulin Classes
IgG
IgA
IgM
IgD
IgE
Immunoglobulin
Classes

41. Immunoglobulin Classes

42. Antibody action Neutralizing antigen Immobilizing bacteria
Agglutinating and precipitating antigen
Enhancing phagocytosis
Activating complement
Defensive system of over 30 proteins
Destroy microbes by causing phagocytosis, cytolysis, and inflammation
Acts in a cascade – one reaction triggers another
3 different pathways ass activate C3
C3 then begins cascade that brings about phagocytosis, cytolysis, and inflammation

43. Immunological memory
Thousands of memory cells exist after initial encounter with an antigen
Next time antigen appears can proliferate and differentiate within hours
Antibody titer measure of immunological memory
Amount of Ab in serum
Primary response
Secondary response faster and stronger

44. Types of Acquired Immunity

45. Self-recognition and Self-tolerance
Your T cells must have
Self-recognition – be able to recognize your own MHC
Self-tolerance – lack reactivity to peptide fragments from your own proteins
Pre-T cells in thymus develop self-recognition via positive selection – cells that can’t recognize your own MHC undergo apoptosis
Self-tolerance occurs through negative selection in which T and B cells that recognize self peptide fragments are eliminated
Deletion – undergo apoptosis
Anergy – remain alive but are unresponsive

46. Self-recognition and Self-tolerance

47. Homeostatic Imbalances of Immunity
HIV

48. Homeostatic Imbalances of Immunity
Allergic Reactions
Autoimmune Diseases
Infectious Mononucleosis
Lymphomas
Systemic lupus Erythematosus