2 - Immune cells and organs Flashcards
(24 cards)
What are primary lymphoid organs?
Where lymphocytes are produced
bone marrow and thymus
The production of lymphocytes is known as _____
LYMPHOPOIESIS
What are secondary lymphoid organs?
Name the 3
where lymphocytes interact with antigens and other lymphocytes
spleen
lymph nodes
MALT (mucosal associated lymphoid tissue)
Where is the thymus located?
below the thyroid gland
What are Hassall’s corpuscles?
whirls of fibroblasts where regulatory T-lymphocytes develop
Where is bone marrow found in the foetus and in adults?
foetus - in all bones (as well as the spleen and liver)
adults - at the end of long, flat bones
What are the changes in the bone marrow during infection/an acute phase response?
increased white cell production (leukocytosis)
What are the 2 types of bone marrow?
RED - produces blood cells
YELLOW - fat
Describe the layout of a lymph node
- highly organised - there are T cell and B cell areas
- B cell areas tend to be on the periphery
- B lymphocytes aggregate into follicles
Describe what changes occur inside lymph nodes during infection
- when there is an ongoing immune response (and there is B lymphocyte proliferation), germinal centers form
- so the lymph node swells
How do lymphocytes enter the lymph nodes from the circulation?
- leave the circulation via high endothelial venules
- directed by gradient of chemokines
What happens in those without a spleen?
people can survive without a spleen
BUT
they are more susceptible to infection by encapsulated bacteria, so should be vaccinated against these bacteria
Where is there lymphoid tissue near the epithelium? Give 2 names
near sites of likely infection
MALT (mucosa associated lymphoid tissue) and the cutaneous immune system
What is found in the Peyer’s patch?
contains germinal centers during immune response
predominantly B cells
What are langerhans cells and where are they found?
dendritic cells of skin and mucosa
they capture antigens in their local environment and migrate via lymphatic vessels to the draining lymph nodes
Why are Cluster of Differentiation markers used?
cannot differentiate between lymphocytes under a microscope
Certain clusters of antibodies recognise certain cell surface proteins
What are the T-cell subsets?
CD4 - T-helper cells, regulatory T-cells - secrete cytokines
CD8 - cytotoxic T-cells - lyse infected cells and secrete cytokines
How are antigens recognised by T-cells?
- T cells only recognise processed antigens
- recognised by the T-cell receptor
- antigens must be presented with an APC on their surface by a MHc molecule
B-lymphocytes express which MHC class?
II
What cell do they present antigens to?
Helper T-cells
How are antigens recognised by B-cells?
- they recognise intact antigens
- recognised by a B-cell receptor
NOTE: the BCR is a membrane anchored form of the antibody they they produce when activated
What happens at the secondary lymphoid tissue?
antigens are presented by APCs
List the 3 antigen presenting cells and where they are located
- dendritic cells - widely spread (skin and mucosal tissue)
NOTE: there are also follicular dendritic cells that are located in the lymph node follicles (but these present to B-cells) - B-lymphocytes - in lymphoid tissue
- Activated macrophages - in lymphoid tissue
NOTE: all these cells (except FDCs) present to T-cells via MHC
What CD markers do ALL B-cells express?
CD19 and CD20
