1. The Lymphatic System & Immunity
Chapter 17

2. Immunity Innate Immunity- fast, non-specific and no memory
Barriers, pH extremes, Phagocytes & NK cells, fever, inflammation, complement, interferon
Adaptive Immunity
Slower, specific & has a memory
Lymphocytes: T-cells & B-cells

3. Lymphatic System Lymphatic tissue – Bone marrow
reticular connective tissue containing lymphocytes
Bone marrow
Lymph- interstitial fluid in lymphatic vessels
Returns excess filtration from capillaries- to circulation
Transport dietary lipids
Maintenance & distribution- lymphoid organs
Filter bacteria and help active defenses

4. Figure 17.1

5. Lymphatic Vessels Begin at lymphatic capillaries
Slightly larger than blood capillaries
Overlapping cells like one-way valve
Pressure will force fluid in
Merge to form larger & larger vessels
Thin walled and more valves than veins
Periodically have lymph nodes
Lymphocytes in capsuled structure
 thoracic duct  L subclavian vein
at junction with jugular
 R. lymphatic duct  R. subclavian vein

6. Figure 17.2a

7. Figure 17.2b

8. Lymphatic flow From tissue to veins
Pumped by muscle & respiratory pumps like venous return

9. Figure 17.3

10. Lymphatic Organs
Primary lymphatic organs- stem cells divide & develop into mature B & T-cells
Red bone marrow & thymus
Secondary organs: immune responses occur
Lymph nodes, spleen & lymphatic nodules

11. Thymus
Two lobed organ
Posterior to sternum, medial to lungs & superior to heart
T-cells divide & mature
Self reactive cells are removed

12. Lymph nodes Scattered throughout the body
Concentrated near mammary glands, axilla & groin
Contain mature B-cells, T-cells dendritic cells and macrophages
Filter lymph, trap foreign substances
Macrophages & lymphocytes destroy most foreign substances

13. Figure 17.4

14. Spleen Between stomach & diaphragm
Contains blood filled venous sinuses and RBCs, macrophages, lymphocytes plasma cells & granular leukocytes
destroys worn or defective blood cells & platelets
Stores platelets
attacks foreign substances in blood
Fetal Hemopoiesis

15. Innate Immunity- Barriers
Skin: Physical & chemical
Epidermal structure & constant shedding
Mucous membranes:
Sticky mucus layer straps microbes, etc. and cilia move it out
Fluids: tears, saliva, perspiration, nasal secretionss
Dilute and antibacterial action
Movement: flow of urine, defecation & vomiting

16. Internal Defenses- Proteins
Interferons-
interfere with viral reproduction in a cell
Complement System
Enhance other immune actions
Break cell membranes
Attract phagocytes
Tag microbial cells for destruction
Transferrins- bind iron & starve bacteria
Antimicrobial peptides: lyse microbes

17. Internal Defenses-Cells
Phagocytes specialized to ingest microbes and cellular debris
Neutrophils
Monocytes macrophages
5-10% of lymphocytes = Natural Killer (NK) Cells
Destroy microbes & tumor cells
Present in lymph nodes & red bone marrow

18. Inflammation Response to tissue damage
Indicated by redness, pain, heat & swelling
1. damage mast cells, basophils & platelets release histamine
 increased permeability & vasodilation in blood vessels

19. Inflammation (Cont.) 2. leakage of clotting proteins into tissue-
Isolate bacteria behind clot
3. phagocytes attracted to site
Neutrophils & macrophages eat & die
4. pocket of dead cells = pus
Moves to body surface or into cavity & is cleared

20. Figure 17.5

21. Fever Abnormally high body temperature
New set-point of thermoregulation system
Normal temperature control action with new set point.
Stimulated by many toxins or internal signals : interleukin-1

22. Adaptive Immunity
Specifically directed against a particular type of invader
Involves cell or antibody directed against a particular antigen
Antigen can be any substance: microbe, food, pollen, tissue
Normally self–tolerant
(does not attack normal body tissue)

23. Maturation of T & B cells
From stem cells in red bone marrow
B cells mature in bone marrow
T cells migrate to thymus
During maturation both make particular proteins in plasma membranes = antigen receptors

24. Types of Responses Cell-mediated- T-cells attack directly
Killer T-cells
Antibody-mediated-
B cells become plasma cells
produce specific antibodies
Helper T cells aid both cell- and antibody-mediated responses

25. Antigens & Antibodies
Major Histocompatability Complex (MHC) = self antigens on cells surface
Unique to each individual
Allows T-cells to recognize foreign material
Antigen triggers plasma cell to produce antibodies
Y-shaped protein with variable antigen binding site on arms
Other end triggers recognition by phagocyte

26. Figure 17.6a

27. Figure 17.6b

28. Triggering Adaptive Response
requires recognizing the foreign antigen
B-ceils can find it anywhere
T-cells need presentation with MHC
Antigen presenting cells (APC) do this
APCs macrophages, dendritic cells & B cells
In respiratory, GI, urinary, reproductive tracts & lymph nodes

29. Processing & Presenting Antigens
APC’s ingest & digest into fragments in vesicles
Synthesize MHC & pack in vesicles
Two vesicles fuse
antigen fragments bind to MHC
Antigen-MHC complex inserted into plasma membrane
Presented to T-cells until a receptor matches & binds

30. Figure 17.7

31. Cell Mediated Immunity
T-ceils also need costimulator
Interleukin-2 (IL-2)
Binding both response
T-cell begins rapidly dividing
Forms a clone of many recognizing cells
Helper T cells-
release IL2, attract phagocytes, stimulate macrophages & B cells
Cytotoxic T cells – kill cells
Work against tumor cells transplanted cells & infected cells
Memory T cells- hang around for years, give rapid response

32. Figure 17.8

33. Figure 17.9

34. B-cells and Antibody- Mediated Response
Hang out in lymph nodes
Respond to antigen (faster if presented)
With IL-2 enlarge, divide and become a clone of plasma cells
Plasma cells produce & release antibodies that bind the antigen
Some remain as Memory B Cells
Ready to respond quickly if antigen met again

35. Figure 17.11

36. Antibody Class Actions
Neutralizing antigen-
Binds & neutralizes toxins
Immobilizing bacteria
Agglutinating-
Connect pathogens to one another easier phagocytosis
Activating complement
Enhancing phagocytosis
Binding attracts phagocytes

37. Immunological Memory Long lasting antibodies & lymphocytes
Many sensitive memory cells 
Much larger & quicker response next time = Secondary Response
Primary response can be naturally acquired
or artificially acquired by vaccination
Killed cells, isolated antigens, parts of viruses

38. Aging Thymus atrophies Fewer responsive T cells
Thus poorer B cell response
Poorer response to new infection