1. The Lymphatic System - includes specialized vessels and organs
Returns escaped fluids back to blood
Monitors fluids for pathogens and mobilizes defenses

2. Lymphatic Characteristics
Not all plasma lost by capillaries returns directly to blood stream
Lymph—excess fluid (+ cell debris, viruses, bacteria, cancer cells if present)
Lymphatic vessels deliver lymph one-way toward heart
‘milked’ by skeletal muscle
Smooth muscle in largest vessels
Valves like veins

3. Lymphatic Capillaries weave between tissue cells and blood capillaries
Minivalves let fluid in, but not out

4. Lymphatic Vessels collect lymph from capillaries
Carry lymph to and from lymph nodes
Return lymph to veins near heart

5. Fewer efferent than afferent = slow flow, better filter
Lymph Nodes are organs that filter (clean up) lymph, house defense cells
Macrophages—engulf and destroy foreign substances
Lymphocytes—provide immune response to antigens
Fewer efferent than afferent = slow flow, better filter

6. Participating…
Fluid from plasma that does not return directly to the bloodstream in capillary beds is known as ___________ that may also contain pathogens. Lymph __________ may be ‘milked’ like veins by skeletal muscle. Lymph __________ filter the lymph slowly because ________ vessels enter than exit each one.
lymph
vessels
nodes
more

7. Other Lymphoid Organs don’t filter lymph, but do maintain lymphocytes for defense
Spleen – filters, stores, and recycles blood
Thymus – programs lymphocytes for immune functions
Tonsils – filters mucus in throat
Peyer’s patches – filters mucus of intestinal lining

8. Body Defenses and the Immune System
Body in constant contact with bacteria, fungi, and viruses
2 defense systems
Innate (nonspecific) defense system – responds immediately to various invaders
Adaptive (specific) defense system – delayed response to specific invaders
Both work in concert

9. Immune System Pathogens = any harmful or disease-causing microorganism
Figure 12.6

10. Innate Body Defenses
Table 12.1 (1 of 2)

11. First Line of Defense = Surface Membrane Barriers
Skin and mucous membranes
Physical barriers – pathogens can’t get through

12. Skin and mucous membranes also fight with chemicals
Acidic pH of skin, vaginal secretions, and stomach kill or inhibit bacteria
Sebum contains antibiotics
Lysozymes in saliva and lacrimal fluid
Digestive enzymes of stomach
Mucus in respiratory and digestive systems

13. Second Line of Defense = Internal Cells and Chemicals (still innate defenses)
Phagocytes (like neutrophils, macrophages)
Engulf (phagocytize) foreign material into a vacuole
Digest with lysosomes

14. Second Line of Defense = Internal Cells and Chemicals (still innate defenses)
Natural killer (NK) cells – release deadly chemicals against ‘non-self’ cells
Can kill cancer cells and virus-infected cells

15. WBCs – neutrophils, macrophages
Second Line of Defense = Internal Cells and Chemicals (still innate defenses)
Inflammatory response
Triggered by tissue damage
Chemicals (like histamine) released
Dilate blood vessels
Attract WBCs
Clot forms
Helps protect and heal
Pathogens trapped and killed by WBCs
Repair begins
WBCs – neutrophils, macrophages

16. Second Line of Defense = Internal Cells and Chemicals (still innate defenses)
Antimicrobial proteins
Interferon – given off by infected cells as a warning
Prevents viral replication (among other things)
Complement proteins – pierce and lyse invaders

17. Second Line of Defense = Internal Cells and Chemicals (still innate defenses)
Fever
Hypothalamus reset by pyrogens (secreted by WBCs)
Inhibits bacterial growth and speeds tissue repair

18. Summary of Nonspecific Body Defenses
Table 12.1 (2 of 2)

19. Participating…
Which of the following are part of the internal defenses of the innate immune system?
A. Phagocytes
B. Natural killer cells
C. Inflammatory response
D. Antimicrobial proteins
E. Fever
F. Mucus membranes

20. Third Line of Defense = Adaptive Defense System
Third Line of Defense = Adaptive Defense System responds to specific pathogens
Antigen specific—identifies pathogen-specific ‘nonself’ antigens (proteins, nucleic acids, pollen, microbes, etc.)
Systemic—pathogen can be identified anywhere in the body
Memory—subsequent exposure = quick & strong response

21. Adaptive Defense System: Third Line of Defense
Humoral immunity = antibody-mediated immunity
Big proteins (antibodies) in body fluids trap pathogens
Cellular immunity = cell-mediated immunity
Living immune cells attack virus-infected cells, cancer cells, and cells of foreign grafts

22. Cells of Adaptive Defense
Lymphocytes respond to specific antigens
B lymphocytes (B cells) – ‘mature’ in Bone marrow; make antibodies
T lymphocytes (T cells) – ‘mature’ in Thymus; help B cells and attack nonself antigen cells
Macrophages – eat invaders and present foreign antigens to T cells among other functions.
‘mature’ = become immunocompetent, i.e. capable of binding with antigens

23. B cells inhabit lymph nodes ‘awaiting’ their antigen
Antigen binding to specific B cell in lymph node
The Chosen One!
B cells only bind directly with ‘free’ antigens = small viruses and toxins
Figure 12.12, step 1

24. Humoral Immune Response
Antigen
Antigen binding to specific B cell in lymph node
‘Chosen’ B cell rapidly divides into clone army
B lymphoblasts
Figure 12.12, step 2

25. 2 types of B cells are produced from clones…
Primary Response (initial encounter with antigen)
Antigen
Antigen binding to specific B cell in lymph node
1. Plasma cells make antibodies
2. Memory B cells
Primary Exposure – Peak antibody levels in 10 days
Figure 12.12, step 3

26. Because of memory cells, secondary response is fast and massive!
Primary Response (initial encounter with antigen)
Antigen
Proliferation to form a clone
Plasma cells
Subsequent challenge by same antigen
Memory B cell
Memory B cells
Secreted antibody molecules
Secondary Response (can be years later)
2-3 day peak at much higher levels!
Figure 12.12

27. Have you had your flu shot? … me neither
Vaccines eliminate slow primary response!
Figure 12.13

28. Participating…
Humoral immunity relies on the production of ______________ by B-cells. B-cells are activated by binding with free ___________ present in the lymph. Memory B-cells protect against secondary infections. How does a secondary response to infection compare with the primary response?
antibodies
antigens
Faster and Stronger!
Primary Response (initial encounter with antigen)
Antigen
Plasma cells
Memory B cell
Memory B cells
Secondary Response (can be years later)

29. Immunoglobin (antibody) Classes
Table 12.2

30. Antibody Function
Figure 12.16

31. Cellular (Cell-Mediated) Immune Response
Unlike B cells, antigens must be ‘presented’ by macrophages to activate T cells

32. Cellular (Cell-Mediated) Immune Response
T cells cloned like B cells, but T cell clones =
Cytotoxic (killer) T cells – bind and kill cells with toxic chemicals
Helper T cells – recruit other immune cells
Prod B cells to make antibodies (among others)
Memory T cells, too!

33. Cytotoxic (killer) T cells release perforins that puncture cell membranes…ouch!
Figure 12.18

34. Participating…
In the cellular immune response, ___________ are activated by ______________ that present antigens from digested pathogens. As a result, _________ T-cells are generated that attack infected or pathogenic cells and _________ are stimulated to make antibodies.
T-cells
macrophages
cytotoxic
B-cells

35. Summary of Adaptive Immune Response
Figure 12.19

36. Summary of Adaptive Immune Response
Figure (1 of 2)

37. Summary of Adaptive Immune Response
Figure (2 of 2)