Lymphoma & Myeloma Flashcards
(97 cards)
What is the product of antigen-independent B-cell differentiation?
what surface markers does it have?
naïve B-cell which is capable of responding to antigen
it expresses:
complete surface IgM and IgD
pan B-cell markers - CD 19, 20, 22, 40, 79a
complement receptors
CD23 and some express CD5

What type of antibody gene do naïve B-cells have?
they have a rearranged but unmutated Ig gene
each B cell is committed to a single light chain (kappa or lambda)
In which locations does B cell development occur?
B cell activation occurs in the secondary lymphoid organs, such as the spleen and lymph nodes
After B cells mature in the bone marrow, they migrate through the blood to the SLOs

By which 2 ways can mature antigen-naïve B cells be activated?
they can be activated by antigens directly
(they apoptose or differentiate into short-lived plasma cells with production of IgM antibody of the primary immune response)
or with the input of T cells

What is a germinal centre?
What type of cells are present here and where do they originate from?
naïve B-cells develop into proliferating IgM expressing B-cell blasts
these have encountered antigen in the paracortex or T-cell zone
they migrate into the centre of the primary follicle to form a germinal centre
the germinal centre is formed from 3-10 naïve B-cells and eventually contains 10,000 - 15,000 B-cells

What are the 4 steps involved in naïve B-cells becoming plasma or memory B cells?
- proliferation
- immunoglobulin somatic hypermutation and class switch
- selection
- differentiation
What happens to the naive B cell following antigen stimulation?
What is the rate of the cell cycle like in the product?
B cells differentiate into centroblasts
these accumulate in the dark zone of the germinal centre
they are highly proliferative with a cell cycle that is completed within 6 - 12 hours

What genes are downregulated within centroblasts?
What is the result of this?
anti-apoptotic genes are downregulated
e.g. BCL-2
pro-apoptotic molecules are present
e.g. CD95
this means only cells which generate highly specific receptors to the antigen in the germinal centre will survive
What is the purpose of somatic hypermutation of centroblasts?
Where does this occur?
somatic hypermutation of the Ig V-region genes of centroblasts occurs within the germinal centre
this increases intraclonal diversity
what do centroblasts mature into?
Where are they found and which process occurs here?
centroblasts mature to non-proliferating centrocytes
these are found in the light zone of the GC
heavy-chain class switch occurs here to alter the Ig constant regions to IgG, IgA or IgE

What happens after heavy chain class switching depending on the centrocytes Ig gene mutation?
if a centrocyte’s Ig gene mutation results in a lower affinity antibody for the antigen, it undergoes apoptosis
if the gene mutation results in increased affinity, the antibody can bind to the antigen
(up until now, this has been trapped by complement receptors on follicular dendritic cells)

What happens once the centrocyte antibody has bound to the antigen?
the centrocytes process the antigen and presents it to T-cells
T-cells express the CD40 ligand
this binds to the B-cell CD40 and rescues it from apoptosis
what is required for differentiation post-GC?
inactivation of BCL6
What step in terminal differentiation is involved in the pathogenesis of Burkitt lymphoma?
downregulation of the myc gene
What is the main mechanism which inactivates BCL6?
the CD40 - CD40 ligand interaction stimulates centrocyte expression of IRF4
IRF4 represses BCL6
BCL6 has an inhibitory effect on BLIMP1, so this is upregulated when BCL6 is downregulated
WHat is the consequence of upregulation of BLIMP1?
BLIMP1 represses PAX5, enabling plasma cell differentiation
it also upregulates XBP1, which helps to regulate plasma cells in their secretory phenotype

What are the different molecules involved in plasma cell development?
- interferon regulatory factor 4 (IRF4)
- B-lymphocyte induced maturation protein 1 (BLIMP1)
- X-box binding protein 1 (XBP1)
- paired box protein 5 (PAX5)
- MYC - a regulatory gene which codes for a transcription factor
What are immunoglobulins?
When are they produced?
They are glycoprotein molecules
they are produced by plasma cells in response to an immunogen
What is the composition of immunoglobulins like?
they are composed of 2 heavy chains and 2 light chains
they are held together by covalent disulphide bonds
each chain has one variable and one constant region

How are immunoglobulins classified?
according to the amino acid sequences in the constant region of the:
heavy chains:
- IgG, IgM, IgA, IgD, IgE
light chains:
- kappa or lambda
What is protein electrophoresis?
What 5 major fractions are normally identfied?
the laboratory technique whereby serum is placed in a gel and exposed to an electric current
5 major fractions normally identified:
- serum albumin
- alpha-1 globulins
- alpha-2 globulins
- beta globulins
- gamma globulins

When is immunofixation performed?
What can it detect?
it is performed when “M-spike” is seen on electrophoresis
it enables the detection and identification of monoclonal immunoglobulins













