1. Aims State the normal functions of the immune system.
State the primary and secondary lymphoid tissues and their functions.
Readings: Abbas & Lichtman, Chapter 1

2. Immunity From the Latin immunis meaning exempt
Immunity refers to all the mechanisms used by the body as protection against foreign environmental agents

3. Normal Functions of the Immune System
Protect from infectious disease or re-infection
Prevent entry/access of microorganisms
Prevent or inhibit growth of microorganisms (Fe++)
Neutralize toxins
Kill or destroy infectious agents
Sequesters (‘walls-off’) infectious agents
Removes effected cells and cellular debris
Surveillance for neoplastic cells

4. Normal Functions of Immune System
The physiologic function of the immune system is to prevent infections and eradicate established infections.
AIDS has demonstrated how important the immune system really is.
Abbas & Lichtman’s Basic Immunology 1-1

5. Normal Functions of Immune System
Vaccinations are effective because they stimulate an immune response to microbes and prime the immune system for a potential infection by that microbe.
Vaccines have eradicated certain infectious diseases.
Abbas & Lichtman’s Basic Immunology 1-2

6. Vaccines Are vaccines safe? - the pertussis paradigm
2 children die in Japan soon after receiving the whole cell pertussis vaccine in That year there were no deaths related to pertussis.
there was a >1300% increase in pertussis cases. In 1979, 41 children died of pertussis in Japan.
An acellular pertussis vaccine now exists which has eliminated the alleged offending antigen.

7. Vaccines Are vaccines safe? - the MMR vaccine
Finnish study from
1.8 million individuals vaccinated with 3 million vaccine doses.
173 potentially serious reactions, with 1 death.
77 neurologic
73 allergic
22 miscellaneous
3.2 serious events per 100,000 vaccines administered.

8. Vaccines
Why vaccinate?

9. Normal Functions of the Immune System
The majority of microorganisms that are encountered are destroyed quickly by the innate (non-specific) immune system
these do not induce an adaptive (specific) immune response
Immune specificity – cells that are capable of attacking influenza virus are not necessarily adept at killing streptococcal bacteria

10. Abnormal Functions of the Immune System
Autoimmunity – immune reaction to self
Immune pathology – often a consequence of the immune response
Collateral damage pathology
Hypersensitivities
Immune deficiencies

11. Cells and Tissues of the Immune System
The major players are the leukocytes (WBCs)
Primary lymphoid tissues give rise to leukocytes
Bone marrow
major site of leukocyte, erythrocyte (red blood cell) and platelet development
all bone marrow-derived cells arise from a pluripotent stem cell
Thymus
encapsulated organ lying anterior to the heart within the rib cage
site of further maturation by a select group of bone marrow cells – T-lymphocytes
haemopoiesis
<haematology> The formation and development of blood cells involving both proliferation and differentiation from stem cells. In adult mammals usually occurs in bone marrow. Haemo = blood; Poiesis = producing or give rise to; Pluripotent = not fixed in regards to its developmental potential
thymus
<anatomy> The lymphoid organ in which T lymphocytes are educated, mature and multiply. It is composed of stroma (thymic epithelium) and lymphocytes, almost entirely of the T-cell lineage. In mammals the thymus is just anterior (in front of) to the heart within the rib cage, in other vertebrates in rather undefined regions of the neck or within the gill chamber in teleost fish. The thymus regresses as the animal matures. – “It’s all down hill after puberty” (the thymus grows through puberty and then atrophys the rest of your life). If you take the thymus out of a fetal mouse – it develops a potentially lethal wasting disease. But if you remove the thymus from an adult mouse – when T cells have already populate the secondary lymphoid organs – not much happens (unless you remove the peripheral T cells with something like whole-body irradiation).

12. Cells of the Immune System
Abbas & Lichtman’s Basic Immunology 1-11

13. Maturation of Lymphocytes
Lymph nodes
Spleen
Mucosal and
Cutaneous
Lymph tissue
Bone
Marrow
Blood
Stem
Cell
Blood,
Lymph
Thymus
Lymphocytes develop from precursors in the generative (1) lymphoid organs.
Bone marrow for B lymphocytes
Thymus for T lymphocytes
Abbas & Lichtman’s Basic Immunology 1-12

14. Maturation of Lymphocytes
Mature lymphocytes enter the peripheral lymphoid organs (lymph nodes, spleen, & other lymphoid tissues) where they respond to foreign antigens and recirculate into the blood and lymph.
These locations are the 2 lymphoid tissues
Here, lymphocytes can interact with other leukocytes and undergo differentiation
haemopoiesis
<haematology> The formation and development of blood cells involving both proliferation and differentiation from stem cells. In adult mammals usually occurs in bone marrow. Haemo = blood; Poiesis = producing or give rise to; Pluripotent = not fixed in regards to its developmental potential
thymus
<anatomy> The lymphoid organ in which T lymphocytes are educated, mature and multiply. It is composed of stroma (thymic epithelium) and lymphocytes, almost entirely of the T-cell lineage. In mammals the thymus is just anterior (in front of) to the heart within the rib cage, in other vertebrates in rather undefined regions of the neck or within the gill chamber in teleost fish. The thymus regresses as the animal matures. – “It’s all down hill after adolescence”

15. Maturation of Lymphocytes
Lymph nodes
Spleen
Mucosal and
Cutaneous
Lymph tissue
Bone
Marrow
Blood
Stem
Cell
Blood,
Lymph
Thymus
Abbas & Lichtman’s Basic Immunology 1-12

16. Secondary (2o) Lymphoid Tissues
Lymph nodes
Spleen
Mucosa-associated lymphoid tissue (MALT)
Pharyngeal tonsils
Peyer’s patches
lung
lamina propria of GI tract
Roitt’s Immunology 7-2