Development of Lymphocytes Flashcards
Advantage of having lymphocytes
- memory
- secondary response - quicker and bigger than the first response
if we don’t have lymphocytes what happens?
we die from overwhelming infection
what do lymphocytes look like?
white cell
small
large nucleus
BCR
- constant region at the bottom
- hyper variable region at the top
complications with MHC
in transplantation - when your body rejects an organ, it is rejecting the MHC - you have to recognise your own MHC
TCR-MHC-peptide binding
MHC-I plus peptide binds to TCR on CD8 T cells
MHC-II plus peptide binds to TCR on CD4 T cells
Thymic Selection
Positive selection - must bind MHC
Negative selection - must not bind self peptides
B cell repertoire selection
Positive selection
identifies immature B cells with completed antigen receptor gene rearrangement
Functional membrane Ig molecules (BCR) provide survival signals
Receptor editing
If high avidity self-recognition - receptor editing changes BCR specificity
Reactivation of RAG genes produces new Ig light chain
If still reactive, rearranges λ light chains
Negative selection
If still auto-reactive, immature B cells with high-affinity self-recognition die by apoptosis in bone marrow or spleen
where do Naïve cells recirculate?
primarily from blood to lymph nodes
Activated B cells transform into?
Plasma cells
“Antibody factories”
also produce CD27+ memory B cells
Key role of Spleen?
in antibody generation
Splenectomy increases the risk of infection
Especially pneumococcal infection – recommend vaccination
key marker of Tissue resident T cells
CD69+
Immune senescence
Lymphocyte function deteriorates with age
Both age of the cell and age of the individual
Telomere shortening
Change in functional attributes
Accumulation of CD57+ cells
CMV infection a key driver of immune senescence
