1. Immune organs

2. Immune organs Central immune organs or primary lymphoid organs
the site that lymphocytes generate and mature into functional cells
Peripheral immune organs or secondary lymphoid organs
the sites that T and B lymphocytes reside in and respond to antigens

3. Immune organs bone marrow thymus spleen lymph nodes
Primary lymphoid organs
thymus
spleen
Secondary lymphoid organs
lymph nodes
mucosal associated lymphoid tissues
(MALT)

4. Immune organs

5. Section I Primary lymphoid organs
I. Bone marrow
the site of generation of all blood cells.

7. Plasticity of HSC
When present in specialized tissue

8. HSC
Theoretically, it should be possible to use stem cells to generate healthy tissue to replace that either damaged by trauma, or compromised by disease.
The signal that regulate their differentiation into specialized cells are still largely unknown.

9. The 2012 Nobel Prize for medicine or physiology
Two pioneers of stem cell research have shared the Nobel Prize for medicine or physiology.
John Gurdon form UK
Shinya Yamanaka from Japan

10. I. Bone marrow
the site of B cell maturation
sequential stages

11. II. Thymus The structure of thymus the site of T cell maturation
Cortex is densely packed with immature T cells, called thymocytes.
Medulla is sparsely populated with mature T cells.

12. The structure of thymus

13. Nude Mice DiGeorge syndrome
a congenital birth defect in human and in mice in which the thymus fails to develop
Nude Mice
DiGeorge syndrome
an absence of T cells and of cell-mediated immunity
an increase in infectious disease

14. The size of the thymus is age-dependent

15. Section II Secondary lymphoid organs
the sites that T and B lymphocytes reside in and respond to antigens
spleen
lymph nodes
mucosal immune system
(mucosal-associated lymphoid tissues, MALT)

16. I. Spleen 1. The structure of spleen
the largest secondary lymphoid organ
1. The structure of spleen

17. Primary and secondary lymphoid follicle
2. Function of spleen
The site of T and B cells residence
T–cell area:
PALS
B–cell area:
Primary and secondary lymphoid follicle
The site that respond to blood-borne antigens

18. 1. The structure of lymph nodes
II. Lymph nodes
1. The structure of lymph nodes
cortex: B cell-rich area
thymus-independent area
paracortex : T cell-rich area
thymus-dependent area
medulla : plasma cell-rich area

19. Primary lymphoid follicles
B cells located in the follicles
secondary lymphoid follicles

20. the path by which naive T and B lymphocytes migrate to lymph nodes

21. 2. Function of lymphoid node
The site of T and B cells residence
B–cell area:
cotex
T–cell area:
paracotex
The site that respond to lymph-borne antigens

22. III. MALT
The mucous membranes lining the digestive, respiratory, and urogenital systems have a combined surface area of about 400 m2
(nearly the size of a basketball court)
the major sites of entry for most pathogens
These membrane surfaces are defended by MALT

23. MALT
loose, barely organized clusters of lymphoid cells in the lamina propria and submucosal area of gastrointestinal, respiratory and urogenital tract.
well-organized structures such as tonsils and appendix, as well as Peyer’s patches

24. The function of MALT
initiate immune responses to ingested and inhaled antigens
local immunity

25. Section III Lymphocytes recirculation
The continuous movement of lymphocytes between blood stream and secondary lymphoid organs is called lymphocyte recirculation

27. Significance of lymphocyte recirculation
it enables the limited number of lymphocytes to search for antigen throughout the body.
it ensures that particular subsets of lymphocytes are delivered to the particular tissue microenvironments.

28. Review
1.Terms
Central immune organs, Peripheral immune organs, lymphocyte recirculation
2. Questions :
Significance of lymphocyte recirculation
The function of thymus, bone marrow, spleen , LN and MALT

29. Study question
List the primary lymphoid organs and summarize their functions in the immune response.
bone marrow: the site of generation of all blood cells and the site of B cell maturation.
Thymus: the site of T cell maturation

30. Study question
List the secondary lymphoid organs and summarize their functions in the immune response.
1. Spleen:
The site of T and B cells residence
T–cell area: PALS; B–cell area: Primary and secondary lymphoid follicle
The site that respond to blood-borne antigens
2. lymph nodes:
B–cell area: cotex, T–cell area: paracotex
The site that respond to lymph-borne antigens
3. mucosal-associated lymphoid tissues, MALT: local immunity

31. Study question At what age does the thymus reach its maximal size?
a. During the first year of life
b. Teenage years (puberty)
c. Between 40 and 50 years of age
d. After 70 years of age