Immune cells and organs Flashcards
Difference between primary and secondary lymphoid organs:
Primary organs: - where develop ie thymus and bone marrow
Secondary organs: lymph nodes, spleen (white pulp), mucosa associated lymphoid tissue (MALT)
Why is primary lymphoid organ defect very serious?
Won’t produce own lymphocyte so only curable with stem cell transport (can manage without some secondary organs) e.g. spleen
What is the structure of the thymus?
Septa–>lobes–>lobules–>Hassall’s corpuscles
What are Hassal’s corpuscules
Whirls of fibroblasts where regulatory T lymphocytes develop
What is the effect of age on the thymus?
- T cell output decreases with age - more fatty tissues in thymus so decreases size
- Total T cell number stay the same but there will be less diversity, more memory cells become oligoclonal - less diverse)
What is the structure of the bone marrow?
Red marrow: produces red cells
Yellow marrow: fat
Where are RBC produced in adults and fetuses?
- In fetus also produced in liver and spleen
- In adults mainly at the ends of long bones filled with marrow (marrow becomes less cellular and more fat droplets)
What is the structure of the lymph node?
- Afferent: in
- Efferent: out
- Lots of lymphocytes inside
- B cell areas on outside, cells aggregate into follicles
What are germinal centers?
Lymphocytes rapidly proliferating to produce antibodies against pathogen so lymph nodes swell
What are the pathways for lymphatic circulation?
Lymphatic vessels: venules, veins, ducts
Lymphatic tissues: nodules, nodes, tonsils
Lymphatic organs: spleen, thymus
How does lymphatic drainage occur?
- Drains fluid to look for antigen then filtered through lymph nodes, allows to find out where in the body the infection is
- Lymphocyte and AP recirculate through lymphatic vessels
What is the structure and function of the spleen?
- Filters antigens in blood
White pulp: Site of lymphocytes
- Immediately surrounds blood vessel in spleen
Red pulp: site of RBC turnover
- Splenic artery brings in blood and surrounded by arteries
Periarterial lymphatic sheath (PALS): area adjacent to arteries/arterioles, mainly T cell area
What is the structure and function of the epithelium?
- heavily defended by immune system
- Near sites of likely infection have lymphoid tissue
- MALT and cutaneous immune system at these places
What is the structure and function of Gut Associated Mucosa?
- Organized into B and T cell areas
- Villi contain draining lymph vessels
- Lots of intraepithelial lymphocytes
- M cells: sample antigens from gut and deliver to lyphocytes in path
What is a Preyer’s patch?
- Predominantly B lymphocytes aggregates
- Have large germinal centers during infection
What is the role of the Langerhans cells in the cutaneous immune system
dendritic cells of skin and mucus
What is extravasation?
process of going from circulation into lymph nodes
How does extravasation occur?
HEV–>chemokine gradient–>leave
see notes
How do we distinguish B and T cells?
make monoclonal antibodies against lymphocyte surface proteins found 1 cluster recognizes particular receptor and other cluster recognizes other
What is a cluster of differentiation?
- Cell surface markers used to discriminate between hematopoietic
- CD markers
What is the structure of TCR receptor?
- all express CD3 integral part of antigen specific receptor
- 2 TCR groups
- CD4+ T helper, regulatory cell - secretes cytokines
-CD8+ cytotoxic T cells - lyse infected cells and
secrete cytokines
- CD4+ T helper, regulatory cell - secretes cytokines
How does TCR recognize antigens?
- Only recognize processed antigens by TCR
- Antigen must be presented by APC on cell surface MHC molecule
What receptors do B cells express?
Express CD19, CD20, MHC Class II
