Lymphoid tissues Flashcards
Lymphatic system components?
Lymphatic vessels and secondary lymphoid tissue.
Examples of lymphocytes.
T cells, B cells and natural killer cells.
What are primary lymphoid tissues?
This is where production of lymphocytes takes place (lymphopoieses).
Primary lymphoid organs.
Thymus, Bone marrow and foetal liver.
What are the two hallmarks of the adaptive immune system?
Specificity and memory.
What does ‘repertoire’ mean in immunology?
The range of genetically distinct BCRs or TCRs present in a given host.
Where is the b cell repertoire generated?
Bone marrow.
Where do B cell mature?
Start of maturation occurs in bone marrow where B cell progenitor is created. Final maturation occurs in periphery in spleen or lymph nodes.
Where does t cell repertoire occur?
Thymus.
What is positive selection?
Does the T cell recognise non self antigens.
What is negative selection?
Does the T cell recognise self antigens. If so then cell apoptosis takes place.
What is thymic involution?
Shrinking of thymus with age. Thymic output decreases with age.
What are secondary lymphoid organs?
Secondary lymphoid organs are where lymphocytes interact with antigens and other lymphocytes.
Secondary lymphoid organs.
Spleen, lymph nodes, appendix, mucosal associated lymphoid tissue.
Properties of lymph nodes.
Distinct T and B cell regions. Afferent(in) and efferent(out) lymp vessels. Arterial and venous connections. Contain germinal centres.
What is a germinal centre?
Anatomically restricted site where B cells undergo mutation and selection to generate high affinity antibodies.
What is the secondary lymphoid tissue within the gut?
Peyer’s patches.
What are peyer’s patches?
A follicle highly enriched with B cells and contain a high frequency of germinal centres.
Why are peyer’s patches and the tonsils always active?
Exposed to lots of antigens.
Where in the gut are peyer’s patches found?
Below epithelium in Ileum.
How do naïve T cells enter lymph nodes?
Selectin binding to endothelial cells. Switch to integrin binding. Transendothelial migration through high endothelial venule.
Through which specialised vessels do naive lymphocytes leave the blood to enter lymph node?
High endothelial venule.
What is an antigen?
Any molecule capable of generating an adaptive immune response.
How do antigens get from the site entry to our lymph nodes?
Diffusion and antigen presenting cells.
Main type of antigen presenting cell?
Dendritic cell.
What antigen presenting cell is found in the epidermis?
Langerhans cells.
What is antigen presentation?
The display of peptides in the major histocompatibility complex I or II proteins such that the T cell receptor can attempt to bind them.
What does ‘CD’ mean? e.g CD19
Cluster of differentiation. Systematic naming of proteins used in the phenotyping of hematopoietic cells.
What CD protein do all T cells have?
CD3.
Where would you find dendritic cells?
Tissues, lymphatics, and secondary lymphoid organs.
What molecular process is the basis of high affinity maturation? How does this process occur?
Somatic hypermutation. An enzyme called activation-induced cytidine deaminase (AID) makes random mutations in the antibody variable region genes. If the mutations result in an antibody that more strongly binds to their targets then these B cells will survive and may differentiate into antibody-producing plasma cells with the new specificity.
