Lecture 4

Question 1

where do lymphocytes originate?

Answer 1

pluripotent haematopoietic stem cells in the bone marrow

Question 2

which transcription factor is expressed to make the common lymphoid progenitor cells stay in the bone marrow and become B-cells?

Answer 2

Pax5

Question 3

What occurs during B-cell development?

Answer 3

B-cell precursors, expressing Pax5, are in the bone marrow responding to cytokines and are delivered to them by bone marrow stroll cells.
Once B cells have rearranged their BCRs, they’re screened in the bone marrow for whether they’re self-reactive or not.
self-reactive B cells are killed in apoptotic cell death
B-cell can then leave the bone marrow and move to secondary lymphoid tissues, lymph nodes, spleen and tonsils.
B-cells may encounter an antigen and then become activated.
If its then activated, the B cell will further differentiate and give rise to either a plasma cell or a memory cell.

Question 4

What are the features of pre-B cell receptors?

Answer 4

delivers signal to the pre b-cell.
no antigen is required
interactions between pre-b cell receptor molecules may be involved

Question 5

what signals are produced from pre-BCR?

Answer 5

turns off RAG-1, RAG-2 genes 
5-6 rounds of cell division
surrogate light chain expression stops
RAG-1 and RAG-2 turned on again
L-chain rearrangement starts

Question 6

How is T-cell development initially similar to that of B cells?

Answer 6

originate fro bone marrow stem cells
re-arrange receptor genes (once in thymus)
express pre-T receptor
elimination of self-reactive T cells be negative selection

Question 7

How is t-cell development different to B-cell development?

Answer 7

undergo development/selection in thymus
alternative lineages - rearrange alpha, beta TCR genes or gamma, delta TCR genes
T-cells expressing alpha, beta TCR must bind with self MHC expressed in thymus - positive selection

Question 8

What occurs in alpha/beta T cell development?

Answer 8

precursors produced in bone marrow migrate to the thymus.
once in the thymus, develop into thymocytes:
1. re-arrange TCR genes and express TCR
2. acquire other markers e.g. CD3, CD4 and CD*
3. undergo positive and negative selection

Question 9

what are the properties of the thymus?

Answer 9

bi-lobed organ in anterior mediastinum
each lobe divided into many lobules
each lobule has outer cortex and inner medulla
cells in the thymus: lymphoid cells epithelial cells, macrophages, dendritic cells

Question 10

How are T cells matured in the thymus?

Answer 10

pro-thymocyte enter the cortex via blood vessels from BM
re-arrangement of TCR genes:
- firstly, re-arrange TCRbeta genes
- expressed along with pre-TCRalpha: pre T cell receptor
- cells proliferated and then re-arrange TCRalpha genes
Express TCR together with CD3
also, express CD4 and CD*