CLINICAL WORKSHOP- MYELOMA immunology Flashcards
What is the epidemiology of myeloma?
uncommon and accounts for 2% of all cases of cancer
It is the 2nd most common haematological cancer
It is about 10% of all haematological malignancies
In the UK, how many new cases of myeloma are there per year?
about 5500 new cases of myeloma per year
Who are most affected by myeloma?
age over 40
The peak average age at diagnosis is 65-70 years old
higher in men and African ethnicity
Why is myeloma often called multiple myeloma?
involves many lesions in the bone marrow
differentiates from a solitary tumour (plasmacytoma)
Where does myeloma originate?
mature B cell malignancy
in plasma cells of the BONE MARROW
Where do B cells normally get activated?
germinal centres of the secondary lymphoid organs
Where do the mutated B cells accumulate?
in the bone marrow
proliferate there
What does monoclonal mean?
B cell can produce only one type of antibody
all mutated B cells create same antibody (MONOCLONAL B CELLS)
What are M proteins?
Antibodies secreted by the malignant B cells are called M proteins
What can M proteins be?
full immunoglobulins
OR
immunoglobulin fragments
What do normal plasma cells look like?
terminally differentiated B cell bigger than B cell big nucleus lots of cytoplasm light area around the nucleus eccentric nucleus (not in the middle)
What does a B cell look like?
smaller than plasma cell
small nucleus
little cytoplasm
What is in the light area around the nucleus of the plasma cell?
ER
large golgi apparatus
What do plasma cells in multiple myeloma look like?
excess plasma cells plasma cells= multiple nuclei Mott cells (in cytoplasm)= contain Ig
What is the normal immunoglobin structure?
2 identical light chains
2 identical heavy chains
What can the light chains of an Ig be?
kappa
lambda
What can the heavy chains of an Ig be?
Gamma, IgG Mu, IgM Alpha, IgA Delta, IgD Epsilon, IgE
Which Ig has the highest serum level?
IgG (5-16g/L)
IgA (0.8-4g/L)
IgM (0.5-2g/L)
IgD and IgE= very low in healthy individuals except if allergy
What are the types of secretory myeloma?
−IgG secretory myeloma (55-60% cases)
−IgA secretory myeloma (20-25% cases)
−free light chain only secretory myeloma (20% cases)−IgD, IgE secretory myeloma is rare
−IgM secretory myeloma is very rare because most of the IgM lies on B cells before they are activated, and so it is usually secreted in low levels
What are the immunological tests for myeloma detection?
serum protein electrophoresis
immunofixation
What does serum protein electrophoresis allow us to identify?
monoclonal immunoglobin- CANT TELL WHAT CLASS AND WHAT LIGHT CHAINS PRESENT
What is the process of electrophoresis?
- load serum onto gel (on negative side)
- electrical fields is passed through gel
- negative proteins migrate to positive side
DEPEND ON SIZE AND CHARGE
What do proteins move depending on in electrophoresis?
CHARGE: strongly negative proteins migrate faster to the positive side of the electrical field
SIZE: smaller proteins also migrate faster to the positive side of the electrical field
What is the order of things seen in serum protein electrophoresis?
- albumin band (THICKEST)- migrated furthest
- globulin alpha 1
globulin alpha 2
globulin beta 1
globulin beta 2 - GAMMA GLOBULINS- NO BAND= FUZZY
What are gamma globulins?
circulating Igs (all classes of Ig) this area has no band= fuzzy area BC Igs are of different sizes, glycosylation etc.
What is densitometry scanning?
the bands are quantified onto a graph using computer software
How is the electrophoresis results different in a myeloma patient?
gamma band= ACC IS A BAND bc only 1 ANTIBODY is made
What does immunofixation allow us to see?
what type of Ig it is and what light chain
What is the process of immunofixation?
- put serum on gel
- gel has rabbit Ig anti-human Ig (antibodies against human IgG)
- rabbit antibody binds to all Human IgG
- Human IgG precipitates
- gel is washed
- when gel is washed all Ig except human IgG will wash out
- run precipitate through electrophoresis
- normal case: see fuzzy smear
in IgG myeloma= will have dark band present - repeated with anti-human IgM, anti-human IgA, anti-human IgE, anti-human kappa light chain, and anti-human lambda light chain to determine the heavy and light chain
What are paraproteins/M proteins?
abnormal proteins
result from proliferation of one clone of plasma
What can paraproteins be?
full immunoglobins (light and heavy chains assembled together)
full immunoglobin + free light chain
just free light chains
just heavy chains= VERY RARE
What are bence jones proteins?
paraproteins can be just free light chains
low molecular weight
can pass in urine
What shows multiple myeloma?
more than 30g/L immunoglobulin in serum
or more than 60g/L immunoglobulin in urine
fragmentation of immunoglobulins bc normal= fully assembled
suppression of normal immunoglobulins will also indicate multiple myeloma
What malignant things can M proteins be in?
multiple myeloma
waldenstrom’s macroglobulinemia
lymphoma
chronic lymphocytic leukemia
What benign conditions can M proteins be present in?
MGUS (monoclonal gammopathy of undetermined significance)
What is the diagnostic criteria for myeloma?
any 2 of:
−M protein/paraprotein in serum and/or urine
−abnormal number of plasma cell, and increased number of plasma cells in the bone marrow
−osteolytic lesions in bones
What are clinical symptoms of myeloma?
anaemia less wbc amyloid deposits in organs viscous blood high infection risk renal failure
How does a myeloma patient get anaemia?
malignant cells degrade bone more Ca2+ released more Ca2+ in serum malignant plasma cells compete with other cells developing in bone marrow so bone marrow is suppressed so you get anaemia and low WBC
Why does the blood become viscous?
lots or proteins in blood (M proteins)
How is renal failure caused?
small light chains pass in kidney, go to urine- block renal tubes= cause renal failure
Why do plasma cells in myeloma go malignant?
plasma cell DNA mutation
- mutations in the proto-oncogenes that control the cell -cycle like cyclins
- deletion of tumour suppressing genes eg TP53
What happens if there is rearrangement between the heavy Ig locus and proto-oncogenes at places in DNA?
- if there is a proto-oncogene which translocates into the immunoglobulin heavy chain locus, it may activate the immunoglobulin locus
- if this proto-oncogene becomes a full oncogene, then it means the cell does not follow the usual rules of proliferation and the cell will become immortal and will refuse to die
What can mutations in the NF-Kappa-B transcription factor promote?
B cell survival
When is IL6 released?
produced by plasma cells
produced by stromal cells in the bone marrow
released when bone is destroyed
IT PROMOTES THE GROWTH OF A MALIGNANT CELL
How does myeloma cause bones to break?
mutated myeloma cells produce growth factors (MIP- 1ALPHA)
they interact with molecules present on stromal cell of bone marrow
increase RANK ligand expression on stromal cells
stromal cells ligate RANK on osteoclasts
osteoclasts activated
inhibit bone formation
IL6 released= supports proliferation and survival of BAD plasma cell
What are the different reasons of kidney failure with myeloma?
hypercalcaemia excess production of light chains- toxic to renal tubular epithelial cells amyloid deposits in kidney infections hyperuricemia
What are the treatments of myeloma?
chemotherapy- control myeloma progression radiotherapy-localised bone pain bone marrow/stem cell transplantation IL6 inhibitor anti-angiogenic proteasome inhibitor- BORTEZOMIB bisphosphonate
What are examples of IL6?
thalidomide, lenalidomide
What do proteasomes do?
proteasome is an organelle inside cells= degrades unwanted and misfolded proteins
it recognizes misfolded/bad proteins because these unwanted proteins are labelled with ubiquitin, and this is what the proteasome recognizes
after breakdown, the cell reuses the amino acids to make new proteins
What do proteasome inhibitors do?
proteasome inhibitors act as a plug on the proteasome and block entry into the proteasome
so now unwanted proteins cannot enter the proteasome
because of this, unwanted proteins will begin to accumulate inside the cell and the cell will become apoptotic
multiple myeloma produces a lot of proteins, and some of these molecules need to be degraded in the proteasome
using these drugs blocks the proteasome, which makes them more sensitive to apoptosis, radiotherapy, and chemotherapy
proteasome inhibitors also reduce the expression of RANK ligands on the stromal cells which inhibit activation of osteoclasts and thus reduce bone lysis−bisph
What do bisphosphonates do?
inhibit bone resorption, reduce fractures, and limit hypercalcemia, and stop destruction of bone mediated by malignant plasma cells
