Lymphoid Tissues Flashcards
What are primary lymphoid tissues?
Organs that produce lymphocytes (e.g. B cells, T cells, Natural Killer cells) - lymphopoiesis : thymus, bone marrow, foetal liver
Adaptive immune response comprised of?
B and T cells
After birth
Bone marrow very cellular - increase in white cell production
Age = bone marrow replaced by fat so restricted lymphocyte production
Increased lymphoeisis
After infection / inflammation
Progenitor
To nk, b or T cell
Or dendritic
Repertoires definition
Range of cells
Thymus
Fatty lymphoid tissue on top of heart
Stepwise defferentiation
Positive Cells deleted when combining genes to produce new receptors goes wrong - nonfunctional
Negative - if it does; it’s removed
Double positive
Age?
Thymus gets smaller AND becomes fatty thymus embolition (double check)
Ability to generate new T cells declines as we age
What are secondary lymphoid tissues?
Spleen
Lymph nodes
Appendix
Mucosal associate
What is the issue with huge T cell / B cell reservoirs?
Many T cells but only one of them can recognise a specific antigen (lost in the entire body)
2nd lymphoid tissue must find a way to get that specific cell to interact with the …
Distribute lymphoid tissue all Dover the body
Lymphocyte can circle around any possible common point of threat
Lymph nodes
Discrete organs - distinct tissues that can be felt
Or regions of larger tissues (some part of the spleen)
Fibrotic reticular cell - recruiting T cells
Look it up
Different zones in the lymph nodes
T cell zone
B cell zone
Spleen
Distinct t and B cell zones
Spleen = Site for antigen screening
Red and white pulp - organised into distinct t and B cell follicles
Epithelial barriers
Physical barrier skin + different tracts
Connected to lymphoid tissues
Below epithelium of the ileum
Receives anthems directly from draining lymph or sample via m cells / dendritic cells
Why there are so many active B cells in our gut?
Ingest many pathogens = major source of infection
More bacteria in our guts than cells in our body
Permanent source of foreign antigens
Immune system responds by secreting Abs
Tonsils
Continuous exposure to oral antigens
Microbes living on top of epithelial layer
