Functional Lymphoid Anatomy Flashcards
(65 cards)
What is the difference between central and peripheral lymphoid tissue in respect to B and T cells?
Central lymphoid tissue (bone marrow, thymus) generates B and T cells (lymphopoiesis) and is responsible for central tolerance
Peripheral lymphoid tissue (LN, spleen, MALT) primes the mixture of B and T cells into effector cells and is responsible for peripheral tolerance
What are the mechanisms in central lymphoid tissue to protect against self-reactive lymphocytes?
Positive and negative selection
What directs cells where to go?
Chemokines and their receptors!
What is the difference between lymph nodes and the spleen?
Lymph nodes process antigen from tissue, where the spleen processes blood borne pathogen
What does MALT do?
protects entryways against pathogenic intruders, and also maintains homeostasis in regards to commensal organisms or benign food particles
What originates in the bone marrow? From what?
B and T lymphocytes, from hematopoietic precursors
Where to B cells mature?
The bone marrow
Does B cell development decline as we age?
No - B cells are continuously produced from the bone marrow, even as we age
What do BM stromal cells do?
Produce signals that direct the development of progenitor and eventually B cells –> in the bone marrow
What is central tolerance?
immarure B cells are checked against self-antigen in the bone marrow and are eliminated if auto-reactive
Where does the final stage of development of immature B cells into mature B cells occur?
in the peripheral lymphoid organs
Where do immature B cells that are not auto-reactive go first?
They are carried via the venous blood to the spleen
describe the general process of T cell development
Progenitor cells migrate to the thymus during embryonic development, become thymoctyes, and mature into T cells
Does the production of T cells decline as we age?
yes!
How are T cell populations maintained?
Long lived T cells and devision of mature T cells in the periphery
What is the thymic cortex, and what is found there?
The outer cortical region
Contains immature thymocytes and scattered macrophages
Most T cell development occurs here
What is the corticomedullary junction, what is found here?
Where T cell progenitors enter
What is the medulla, and what is found there?
Inner region
More mature single positive T cells, along with dendritic cells and macrophages
What is the thymic cortical stroma, and what is found there?
Network of epithelia where T cell precursors reside
Provides environment for T cell development
has epithelial cells that express both MHCI and MHCII on their surface
What is the first step in T cell development?
progenitors enter at the corticomedullary junction and migrate to the outer cortex
What is the receptor status of thymocytes proliferating in the outer cortex?
they are double negative
What does double negative mean?
They lack both the CD3+ T cell receptor complex and CD4+/CD8+ co-receptor
What happens when thymocytes leave the outer cortex?
They migrate further into the cortex and undergo receptor rearrangement to become CD3+ and CD4+CD8+ double positive thymocytes
What happens if a thymocyte can’t recognize self peptide/self MHC?
They die by apoptosis
