Lymphoid tissues Flashcards
What are primary lymphoid tissues?
Where lymphocytes are produced?
What are lymphocytes?
B-cells
T-cells
Natural Killer cells
What are the primary lymphoid organs?
Thymus
Bone marrow
Foetal liver
What do T-cells and B-cell comprise?
The adaptive immune response
Very specific
Memory for secondary encounter
Where is the primary site of haematopoiesis?
Bone marrow
When does white cell production increase?
During infection
What is Repertoire?
The range of the genetically distinct b-cell receptors and t-cell receptors that any given person has
Larger repertoire- more threats can be recognised
What happens in the thymus?
Immature T-cells migrate to the thymus where they undergo a step wise differentiation process
What is positive selection?
Whether the T-cell receptor that the cell expresses is functionally correct.
What is negative selection?
Will it react against our own body? If yes, undergoes apoptosis
What is meant by self?
Anything recognised by immune system as part of your normal molecular make-up
What is meant by non-self?
Anything recognised by the immune system as foreign
What is thymus involution?
The shrinking of the thymus with age
Associate with a change in structure and a reduced mass
How many T-cell in the blood roughly?
3.75x10^11
How many antigens can our body recognise?
10^15-10^20
How does a small population of cells (e.g 1) find a foreign protein in a human body?
Secondary lymphoid organs are where
Name some secondary lymphoid organs
Lymph node
Spleen
Appenix
Mucosal associated lymphoid tissue
How are the lymphoid organs connected?
Lymphatic system and the blood
What are the two types of lymphoid tissue?
Discrete organs e.g lymph nodes/adenoids
Distinct regions with a tissue e.g spleen
What are the main features of lymph nodes and the spleen?
Distinct T and B cell zones
Afferent (in) and efferent (out)
Arterial and venous connection
What are epithelial barriers?
First line of defence against infection
Physical barrier
Extensive lymphatic network
What are gut associated lymphoid tissue?
Specialised secondary lymphoid tissues called Peyer’s patches
Found below the epithelium of the ileum of the small intestine
Follicle is highly enriched with B-cells and contains a high frequency of germinal centres
What is a germinal centre?
Anatomically restricted site where B cells undergo mutation and selection generate high affinity antibodies
What are tonsils?
Pharyngeal, tubular, palatine and lingual tonsils encircle the oral and nasal cavity- form the Waldeyer ring
How does the lymph circulate?
Fluid drained from between tissue cells absorbed into lymph
2-4 litres of lymph are returned to the blood each day via superior vena cava
How often does each naïve T-cell recirculate?
Every 24 hours
What are the 4 steps of T-cell extravasation?
Rolling
Activation
Arrest/Adhesion
Transendothelial migration
What are dendritic cells?
Professional antigen presenting cells
Range of migratory and tissue resident variety
What is antigen presentation?
The display of peptides in the major histocompatibility complex I or II proteins such that the T-cell receptors can attempt to bind them
What is the function of lymphoid organs?
To provide immunity
How are lymphoid organs distributed?
Distributed around the body at a high frequency in areas routinely exposed to ‘danger’
There is regular flow of immune cells and fluid increasing chance of interactions
What does CD stand for?
Cluster of Differentiation
Define Cluster of Differentiation
Internally recognised standard for the systematic making of proteins
used in the phenotypic of hematopoietic cells
How is identification of cells of the immune system carried out?
Analysis of what CD proteins have on their surface
e.g.
B-cells: CD19
T-cells: CD3
