CHAPTER 6 - LYMPHOID ORGANS Flashcards
LYMPHOID ORGANS
- Divided into two:
Primary and Secondary lymphoid organs
- Main producers of lymphocytes (B cells and T cells)
Primary
o Followed by release to the circulation
then to the secondary lymphoid organ (SLO)
Primary
- Provide appropriate microenvironments or the development and maturation of lymphocytes
Primary
- Thymus
Primary
- Bone marrow
Primary
- Site of maturation and site where lymphocytes can perform their main functions.
Secondary
- Trap antigen from defined tissues or vascular spaces and are sites where mature lymphocytes can interact effectively with the antigen
Secondary
o Tonsils, spleen (lymph nodes (Lymphatics and skin), Peyer’s patches, appendix, and mucosa- associated lymphoid tissue (MALT)
Secondary
function as potential sites for contact with foreign antigen, and they increase the probability of an immune response.
Secondary
- Adenoids
Secondary
- Tonsils
Secondary
- Lymph nodes
Secondary
- Spleen
Secondary
- Peyer’s Patches
Secondary
- Appendix
Secondary
- MALT
Secondary
– lymphatics and skin
Lymph nodes
– entry through circulation
Spleen
– a specialized type of MALT and are located at the lower ileum of the intestinal tract
Peyer’s Patches
- Largest tissue of the body (adult: 1300 to 1500g)
Bone Marrow
Bone Marrow
- Two parts:
- Red marrow
- Yellow Marrow
– produces blood cells
Red marrow
– higher percentage; cannot produce HSC
but adipose/fat cells instead
Yellow Marrow
- Primary function: Primary source of pluripotent stem cells that give rise to all hematopoietic stem cells (HSC) that fives rise to other blood cells
Bone Marrow
- Major organ for B cell maturation (“B” cells = “B”one marrow) gives rise to the precursor cells of the thymic lymphocytes.
Bone Marrow
- common lymphoid progenitor
HSC
- common myeloid progenitor
HSC
– produced in the BM then undergo further maturation to a B cell (either released to the circulation or proceeds to SLO)
B cell progenitor
– produced in the BM then proceeds to the thymus for further maturation
T cell progenitor
- Center for antigen-independent lymphopoiesis (production of lymphocytes)
Bone Marrow
o Without the stimulus of an antigen
Bone Marrow
o Maturation does not end as B cells and T cells
Bone Marrow
= Plasma cell (can produce
Abs)
B cell + Ag
= memory B cell (remembers Ag encounter)
T cell + Ag
o Produce large numbers of B cells, each with unique
antigen receptors (antibodies) such that, overall, there is sufficient B cells diversity to recognize millions of microbial antigens in the environment.
Bone Marrow
- Same to the concept of Ab-diversity by Paul Ehrlich (Side Chain Theory)
Bone Marrow
- An Ag looks for a particular cell with a specific receptor to become an Ab
Bone Marrow
- To avoid autoimmunity (attacking of own cells due to overreactivity of B cells)
Eliminate B cells with antigen receptors having high affinity for self-molecules.
61-89% = (?)
T cells (Most abundant)
10-20% = (?)
B cells
- Primarily involved in adaptive/specific
immunity
T cells & B cells