Leukaemia and Lymphoma Flashcards
Where does normal B cell development start?
In the bone marrow
What is B cell production stimulated by?
Growth factor and cytokine production that initiates gene regulation commiting the common lymphocyte progenitor to B cell lineage
How does a progenitor B cell differentiate to a mature B cell?
- Rearrangement of Ig Heavy Chain Genes
2. Rearrangement of Ig Light Chain Genes
What chains are brought together to form the heavy chain?
Kappa and Lambda chains
What are most B cell lymphomas derived from?
Germinal Centre Cells
What are the 4 B cell lymphomas (most common to least common)?
- Diffuse Large B Cell Lymphoma
- Follicular Lymphoma
- Mantle Cell Lymphoma
- Burkitt’s Lymphoma
What is a germinal centre?
A site within secondary lymphoid organs (lymph nodes and the spleen) where mature B cells proliferate, differentiate
What surrounds the germinal centre?
Mantle zone
Where does mantle cell lymphoma arise from?
Naive B Cells in the mantle zone
What do BL, FL and DLBCL arise from?
Germinal centre B cells
What drives Burkitt Lymphoma?
Chromosomal translocation
What kinds of Burkitt Lymphoma can occur?
High grade amd low grade, Sporadic and Epidemic, Immunodeficieny associated
What is the name for the histological appearance classically seen with BL?
Starry Sky
How do lymphoma cells appear?
Large nucleus with very little cytoplasm. Vacuoles within the cytoplasm.
What are 2 examples of epidemic causes of Burkitt lymphoma?
- Epstein Barr Virus
- Malaria
How does EBV cause BL?
Attaches to and activates B-lymphocytes CD21 receptor
Where is sporadic BL more common?
In the western world
Which chromosomes are translocated in BL?
8 and 14 (t(8;14))
What does the 8:14 translocation cause?
MYC brought into the antibody heavy chain locus so increased expression influenced by antibody HC enhancer element
Where does the translocation tend to occur within the body in sporadic BL?
Later, within the germinal centre
Where does the translocation tend to occur within the body in epidemic BL?
Within the bone marrow
What happens in cells with increased deregulated cMYC expression?
Cell cycle progression factors increase, allowing cell transformation and persistence of cells with decreased affinity (instead of apoptosis) -> tumorigenesis -> cancer
What can help distinguish BL from other lymphomas?
FISH - get red and green probes mixing -> orange fusion signal on the translocated genes
What is Follicular lymphoma?
B cell lymphoma where abnormal lymphocytes build up in the lymph nodes
Is FL generally lower or higher grade?
Lower, with a slower clinical course
How does FL present often?
Painless swelling in neck, armpit or groin
What chromosomal translocation causes FL?
t(14;18)
What does the t(14;18) cause?
The antibody HC gene enhancer element is brought to the bcl-2 gene area and incresases the bcl-2 expression
What does Bcl-2 have an important role in?
Apoptosis
Which types of Bcl-2 genes are amplified in FL?
Anti-apoptotic subfamily
What do these anti-apoptotic Bcl-2 proteins do?
Help stabilise the outer mitochondrial membrane, and prevent pro-apoptotic Bcl-2 proteins from binding.
What is diffuse large b-cell lymphoma?
The most common type of high-grade (fast‑growing) non-Hodgkin lymphoma, where the B cells are abnormally large and spread diffusely.
What is the median age of diagnosis with DLBCL?
66
What translocation commonly causes DLBCL?
3q27 translocation affecting the BCL6 gene
How does the 3q27 translocation affect the BCL6 gene?
It amplifies it and deregulates it
What does BCL6 normally do?
It is a transcription repressor of other genes (oncogenes and TSGs) to allow rapid B cell differentiation, especially in response to antigen-presentation
Where is BCL 6 normally only active?
Within the germinal centre
How does this BCL6 amplification/deregulation cause DLBCL?
Overexpressed BCL6 still represses tumour suppressor genes but mutated oncogenes escape regulation causeing aggressive lymphoma
How is LBCL classified?
Based on expression of 3 genes
What are the 3 genes?
- CD10
- BCL6
- MUM1
What TSG is frequently disrupted in LBCL?
BLIMP1
Which viruses are indirectly involved in lymphoma?
- HCV
- HIV
- EBV
Which viruses are directly involved in lymphoma?
- HHV8/KSHV
- HTLV1
What is primary effusion lymphoma?
A rare NHL associated with HHV8
When is primary effusion seen?
In immunosuppressed patients (either HHV8 infected AIDS pts or transplant recipients recieving high doses of immunosuppression)