1. The Lymphatic System and Immunity

2. Introduction
The body harbors about 10,000 times as many bacterial cells as human cells
Some beneficial
Some potentially disease-causing
Immune system—not an organ system, but a cell population that inhabits all organs and defends the body from agents of disease
Especially concentrated in the true organ system: lymphatic system
Network of organs and vein-like vessels that recover fluid
Inspect it for disease agents
Activate immune responses
Return fluid to the bloodstream

3. Lymphatic system
The lymphatic system
Contains cells, tissues, and organs responsible for defending the body
Lymphocytes resist infection and disease by responding to
Invading pathogens such as bacteria or viruses
Abnormal body cells such as cancer cells
Foreign proteins such as toxins

4. The Lymphatic System

5. The Lymphatic system consists of
Lymphatic vessels
Lymphoid tissues and organs
Lymphocytes and supporting phagocytic cells
Functions of lymphatic system
Blood volume maintenance
Primary function is production, maintenance, and distribution of lymphocytes
Lymphocytes must:
Detect where problems exist
Be able to reach the site of injury or infection

6. Lymphatic Capillaries

7. Major lymph-collecting vessels
Superficial and deep lymphatics
Thoracic duct
Cisterna chyli
Right lymphatic duct

8. Lymphatic Vessels Collecting vessels course through many lymph nodes
Six lymphatic trunks drain major portions of body
Two collecting ducts
Right lymphatic duct: receives lymph from right arm, right side of head and thorax; empties into right subclavian vein
Thoracic duct: larger and longer, begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, left arm, left side of head, neck, and thorax; empties into left subclavian vein
Subclavian veins—collective point from thoracic duct

9. Drainage of Thorax Internal jugular veins Right jugular trunk
Left jugular trunk
Right lymphatic duct
Thoracic duct
Right subclavian trunk
Left subclavian
trunk
Right
bronchio-
mediastinal
trunk
Left
bronchiomediastinal
trunk
Azygos vein
Thoracic duct
Thoracic lymph
nodes
Hemiazygos vein
Diaphragm
Cisterna chyli
Intestinal trunk
Right lumbar trunk
Left lumbar trunk
(a)

10. The Relationship between the Lymphatic Ducts and the Venous System

11. Lymphatic Cells Natural killer (NK) cells
Large lymphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or have turned cancerous
Responsible for immune surveillance
T lymphocytes (T cells)
Mature in thymus
thymus dependent cells
B lymphocytes (B cells)
Activation causes proliferation and differentiation into plasma cells that produce antibodies
bone marrow-derived cells

12. The Derivation and Distribution of Lymphocytes

13. Lymphoid tissue
Connective tissue dominated by lymphocytes
Lymphoid nodules
Lymphocytes densely packed in areolar tissue
Found in the respiratory, digestive, and urinary tracts
MALT (mucosa-associated lymphoid tissue)
Collection of lymphoid tissues linked with the digestive system
Aggregated lymphoid nodules or Peyer’s patches
Tonsils: in the pharynx, 5 tonsils: left and right palatine, a pair of Lingual tonsils, and a single pharyngeal tonsil (adenoids).

14. The Tonsils
Palate
Pharyngeal
tonsil
Palatine
Lingual

15. Lymphoid organs
Lymph nodes – function in the purification of lymph
Afferent lymphatics – carry lymph to nodes
Efferent lymphatics – carry lymph from nodes

16. The Thymus

17. The Spleen Largest mass of lymphoid tissue
Cellular components form pulp
Red pulp contains RBC
White pulp similar to lymphoid nodules
Spleen functions include
Removal of abnormal blood cells and other blood components
Storage of iron
Initiation of the specific immune response

18. Lymphatic system and body defenses
Nonspecific defenses
Do not distinguish one type of threat from another
7 types
Specific defenses
Protect against particular threats
Depend upon the activation of lymphocytes

19. Nonspecific Defenses

20. Nonspecific Defenses, Physical barriers
Keep hazardous organisms outside the body
Includes hair, epithelia, secretions of integumentary and digestive systems

21. Nonspecific Defenses, Phagocytes
Remove cellular debris and respond to invasion by foreign pathogens
Monocyte-macrophage system
Microphages – Neutrophils and eosinophils
Exhibit chemotaxis

22. Nonspecific Defenses, Immunological surveillance
Constant monitoring of normal tissue by NK cells
NK cells
Recognize cell surface markers on foreign cells
Destroy cells with foreign antigens

23. Nonspecific Defenses, Interferons (cytokines)
Small proteins released by virally infected cells
Trigger the production of antiviral proteins

24. Nonspecific Defenses, Complement system
Cascade of ~11 plasma complement proteins (C)
Destroy target cell membranes
Stimulate inflammation
Enhance phagocytosis

25. Complement Activation

26. Effects of Complement Activation
Stimulation of Inflammation
Attraction of Phagocytes
Enhancement of Phagocytosis
Destruction of Target Cell Membranes

27. Nonspecific Defenses, Inflammation
Localized tissue response to injury producing
Swelling
Redness
Heat
Pain

28. Nonspecific Defenses
Exogenous pyrogens: bacteria and toxin produce by them, viruses.
Endogenous pyrogens: as neutrophils and macrophages attack pathogens, they secrete a variety of polypeptides that act as a endogenous pyrogen. Example: Interleukin 1 or IL1
Every 1oC rise in temperature, metabolic rate goes up by 10%.

29. Specific Defenses

30. Types of Immunity

31. Properties of immunity
Specificity – activated by and responds to a specific antigen
Versatility – is ready to confront any antigen at any time
Memory – “remembers” any antigen it has encountered
Tolerance – responds to foreign substances but ignores normal tissues

32. The immune system response
Antigen triggers an immune response
Activates T cells and B cells
T cells are activated after phagocytes exposed to antigen
T cells attack the antigen and stimulate B cells
Activated B cells mature and produce antibody
Antibody attacks antigen

33. An Overview of the Immune Response

34. Major types of T cells
Cytotoxic T cells (TC) – attack foreign cells
Helper T cells (TH) – activate other T cells and B cells
Suppressor T cells (TS) – inhibit the activation of T and B cells

35. Antigen-glycoprotein combination appears on a cell membrane
Antigen presentation
Antigen-glycoprotein combination appears on a cell membrane
Called MHC proteins (Major Histocompatibility Complex)
Coded for by genes of the MHC
T-cells sensitive to the antigen are activated upon contact

36. MHC classes Class I – found on all nucleated cells
Class II – found on antigen presenting cells and lymphocytes

37. Antigens and MHC Proteins

38. Antigens and MHC Proteins

39. Antigens and MHC Proteins

40. Lymphocytes respond to antigens bound to either class I or class II MHC proteins
Antigen recognition
T cell membranes contain CD markers
CD3 markers present on all T cells
CD8 markers on cytotoxic and suppressor T cells
CD4 markers on helper T cells

41. Activation of CD8 cells Responds quickly giving rise to other T cells
Cytotoxic T cells – seek out and destroy abnormal cells
lymphotoxin
Memory TC cells – function during a second exposure to antigen
Suppressor T cells – suppress the immune response

42. Antigen Recognition and the Activation of Cytotoxic T Cells

43. Antigen Recognition and the Activation of Cytotoxic T Cells

44. Activation of CD4 T cells by antigens presented on class II MHC proteins
Produces helper T cells and memory T cells
Activated helper T cells
Secrete lymphokines that coordinate specific and nonspecific defenses
Enhance nonspecific defenses
Stimulate the activity of NK cells
Promote activation of B cells

45. Antigen Recognition and Activation of Helper T cells

46. A Summary of the Pathways of T Cell Activation

47. B cell sensitization of activation
Sensitization – the binding of antigens to the B cell membrane antibodies
Antigens then displayed on B cell Class II MHC
TH cells activated by same antigen stimulate B cell
Active B cell differentiates into Memory B Cell or Plasma cell
Plasma cells synthesize and release antibody

48. The Sensitization and Activation of B Cells

49. Antibodies structure
Antibodies are Y-shaped proteins consisting of:
Two parallel polypeptide chains
Heavy chains and light chains
Constant region and variable region
Antigen binding site

50. Antibody Structure

51. Actions of antibodies include:
Neutralization
Agglutination and precipitation
Activation of complement
Attraction of phagocytes
Opsinization
Stimulation of inflammation
Prevention of adhesion

52. Classes of Antibodies (immunoglobins)
IgG – resistance against many viruses, bacteria and bacterial toxins
IgE – accelerates local inflammation
IgD – found on the surface of B cells
IgM – first type secreted after antigen arrives
IgA – primarily found in glandular sec