Primary lymphoid tissues Flashcards
What are the primary lymphoid tissues?
Bone marrow and thymus
Another name for primary lymphoid tissues?
Central lymphoid organs
What cells are immune cells derived from?
haematopoietic stem cells
Other than immune cells, what do haematopoietic stem cells also become?
Platelets and red blood cells
Two types of bone marrow
Red and yellow
What is red bone marrow involved in?
Haematopoiesis
What is yellow bone marrow made up of?
Adipocytes
At birth, where does haematopoiesis occur?
all medullar cavities of bone
Where is haematopoiesis restricted to in adulthood?
Axial skeleton
In adulthood, what do the medullary cavities have in them?
Adipocytes
What are both T cells and B cells derived from?
Common lymphoid progenitor
Where do B cells develop and mature?
Bone marrow
Where do T cells mature?
Thymus
Where is the thymus?
Superior and anterior mediastinum, superficial to the heart and posterior to the sternum
When is the thymus the largest and most active?
In childhood
Where are T cells that recognise self MHC positively selected for?
Cortex of thymus
What percentage of T cells fail positive selection?
95%
What presents T cells in the cortex with MHC?
Cortical epithelial cells
Where does negative selection of self reactive T cells occur?
Medulla
What cells present peptides in the medulla?
Dendritic cells
