7. Lymphoid System
Primary lymphoid organs
Bone marrow
Thymus
Secondary lymphoid organs
Organized
Lymph nodes
Spleen
Tonsils
Less organized
8. Lymphatic System
Network of vessels
Collects fluid from tissues
Major cell is lymphocyte
Unidirectional
Often first place where antigens are
detected
12. Thymus
Function
Takes in immature T cells and puts out
mature (immunocompetent) T cells
Increased diversity of T cells
T cell selection
13. Thymus
T cell selection
Based on MHC/Ag complex recognition
Recognize MHC/Non self AG complexes
Recognize MHC/Self Ag complexes
Do not recognize MHC/Ag complexes
Athymic condition
Natural
Other
14. Bone marrow
Structure
Microscopic
Less well defined than thymus
Role of stromal cells
Function
Hematopoiesis
B cell maturation
B cell selection
Puts out mature, naive B cells
20. Lymph Nodes
Function
1st line of response to antigens
Secondary follicle (Germinal center) is site of B
cell proliferation, mutation, differentiation
Specificity is high
Lympadenopathy
Lymphodoema
21. Spleen
Structure
Gross
Ovoid organ in upper left quadrant of abdomen
Microscopic
Compartmentalized
Red pulp
White pulp
Periarticualr lymphoid sheath
Site of Ag presentation
Major cell types
Lymphocytes
Macrophages
Dendritic cells
RBCs
22.
23. Spleen
Function
Filters out older blood cells
Responds to Ag in circulatory system
Produces activated B cells
Production of blood cells
Reservior function
Splenagamy
Splenotomy
24. Tonsils
Collection of lymphoid tissue facing into
the aerodigestive track
1st line of defence against indested or
inhaled foreign pathogens
Germinal centers appear in response
to Ag
Produce T lymphocyte in a different
way from spleen’s
Protective role in URI (Tonsillitis)