Proteins Flashcards
1
Q
Albumin
- amount in serum
- analbuminemia results in
- albumin alleles
- clinical utility
A
- Most abundant serum protein
- Analbuminemia results in mild edema and hyperlipidemia
- Several albumin alleles (most common = albumin A); variant alleles may result in bisalbuminemia (benign)
-
Clinical utility:
- Assessing nutritional status: halflife of albumin is 17 days
- Assessing hepatic synthetic function
- Assessment of renal glomerular function
- Negative acute phase reactant
- Diabetic control: glycated albumin is indicator of short term glycemic control
- Maintains serum oncotic pressure
2
Q
Prealbumin
- SPEP
- function
- clinical utility
A
- AKA transthyretin
- Not normally seen on SPEP
- Functions in serum to bind
- thyroxine
- retinol binding protein: vitamin A complex
- Clinical utility
- Assessment of nutritional status
- Negative acute phase reactant
- Prealbumin band is a hallmark of CSF protein electrophoresis
3
Q
Alpha1-antitrypsin
- SPEP appearance
- genetics (number of alleles, most common alleles)
- clinical utility of SPEP
A
- Major component of the alpha1 band
- AAT gene (SERPINA1) highly polymorphic with > 100 alleles
- Most common allele is PiM
- Most common genotype is PiMM
- SPEP can detect AAT deficiency (homozygotes for PiZZ) showing a diminished alpha1 band
4
Q
Electrophoretic band
alpha1-alpha2 interface
A
- Gc globulin: binds vitamin D
- alpha1-antichymotrypsin: positive acute phase reactant
- alpha1-acid glycoprotein: minor component of alpha1 band normally but major component of the increased alpha1 band in acute inflammatory states
5
Q
alpha2 electrophoretic band
A
-
alpha2-macroglobulin:
- relative concentration elevated in liver and renal disease
- large size prevents its loss in nephrotic syndrome, leading to a relative 10 fold rise in concentration
-
Haptoglobin:
- binds free hemoglobin
- rapidly depleted in intravascular hemolysis
- does not bind myoglobin
- positive acute phase reactant
-
Ceruloplasmin
- binds copper
- low ceruloplasmin not detectable with SPEP
- positive acute phase reactant
- decreased in Wilson disease
6
Q
alpha2-beta interface electrophoretic band
A
- Usually empty
- Hemoglobin, usually absent from serum, may be present here when there is hemolysis (a possible pseudo M spike)
7
Q
Beta1 electrophoretic band
A
Transferrin
- Transports ferric (Fe3+) iron
- Normally 30% saturated
- Markedly increased in iron deficiency
- Asialated transferrin (tau protein) and a double transferrin peak are hallmarkes of CSF electrophoresis
- Carbohydrate deficient transferrin a marker for alcohol use
8
Q
beta1-beta2 interface
A
Beta-lipoprotein
- LDL
9
Q
Beta2 electrophoretic band
A
- IgA
- Fibrinogen, usually absent from serum
- May be present in the beta-gamma interface when there is incomplete clotting (a possible pseudo M spike)
- C3
- positive acute phase reactant
- C3 breakdown products may produce a pseudo M spike
10
Q
gamma1 electrophoretic band
A
gamma globulins
- positive acute phase reactants
11
Q
gamma2 electrophoretic band
A
CRP
- Marker of inflammation
- produces a small band
- high sensitivity assays can detect CRP as little as <0.5 mg/L resulting in 3 tiers of CRP
- Normal CRP: <2-3 mg/L
- High level CRP elevation: >10 mg/L usually indicates active inflammation such as collagen vascular disease, infection, etc.
- Low level CRP elevation: 3-10 mg/L; indicates cellular stress and correlated with higher all cause mortality, poor outcome following cardiovascular events
12
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16
Q
What does a normal serum electrophoresis look like
A
- Nearly invisible prealbumin band
- Large albumin band
- Small peaked alpha1
- Broad alpha2
- Biomodal beta
- Broad gamma
17
Q
Bisalbuminemia
A
- Heterozygotes for albumin alleles
- SPEP shows double albumin spike
- No clinical consequence
18
Q
alpha1-antitrypsin deficiency electrophoresis
A
Can be detected with SPEP (but not the most S and S assay)
19
Q
Nephrotic syndrome electrophoresis
A
- Loss of small serum proteins, particularly albumin
- Large protein molecules retained
- Decrease of all bands except alpha2 band that contains alpha2 macroglobulin
20
Q
Beta-gamma bridging
A
- Indicative of cirrhosis and caused by increased serum IgA
- Hypoalbuminemia
- Blunted alpha1 and alpha2 bands
21
Q
Monoclonal gammopathy
A
- Immunochemically homogeneous immunoglobulin M protein in the serum
- SPEP shows a prominent, discrete, dark band within gamma, beta, or rarely alpha2
- M protein usually intact immunoglobulin, composed of 2 heavy and 2 light chains
- Sometimes light chain only
- Rarely a heavy chain only
- Biclonal gammopathy in 3-4% of cases (if IgA, more likely due to the appearance of both monomers and dimers, especially if IgA light chain)
- 10% of patients show only hypogammaglobulinemia
- Immunofixation or immunosubtraction is indicated to characterize the M protein
- urine should be screened for monoclonal free light chains
- serum free light chain levels should be evaluated
- M spike is most commly the result of PCN, Waldenstrom macroglobulinemia (lymphoplasmacytic lymphoma) or CLL
22
Q
Pseudo M spikes
A
- Fibrinogen (incompletely clotted sample)
- Hemoglobin (hemolyzed sample)
- Elevated CRP
- Elevated transferrin
- Antibiotics
- Radiocontrast agents
- Serum tumor markers (e.g., CA19-9)
- C3
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29
Q
CSF protein electrophoresis
A
- CSF normally contains proteins in serum, but in smaller quantities
- Prominent prealbumin band and a double beta (transferrin) band
- Electrophoresis used to support a diagnosis of multiple sclerosis by finding oligoclonal bands, which should be absent in the serum
30
Q
Urine Protein Electrophoresis
A
- Glomerular proteinuria pattern:
- strong albumin alpha1 and beta bands
- large proteins (persistence of some filtering function) absent
- small proteins (tubular reabsorption) absent
- Intermediate proteins are left in urine
- Albumin
- AAT
- Transferrin
- Tubular proteinuria
- Weak albumin band
- strong alpha1 and beta bands
- Overflow proteinuria pattern
- Monoclonal light chain (Bence Jones proteinuria) usually
- Could also be myoglobin or hemoglobin
31
Q
Cryoglobulins
- define
- detection
A
- Immunoglobulins that precipitate reversibly at low temperature
- Detection
- Draw blood at 37 degrees until clotted
- Centrifuge at 37 degrees
- Place serum at 4 degrees for 3 days
- Centrifuge at 4 degrees
- Any precipitate can be washed and electrophoresed and immunofixed
32
Q
Type I, II, and III cryoglobulins
A
- monoclonal immunoglobulins associated with MM or Waldenstrom
- Mixture of monoclonal IgM and polyclonal IgG
- IgM has RF activity (anti IgG)
- most common type of cryoglobulin
- Mixture of 2 polyclonal immunoglobulins, typically IgG and IgM; IgM has RF activity
33
Q
Mixed cryoglobulinemia
A
- Associated with
- Lymphoproliferative disorders
- Chronic infection
- Chronic liver disease
- Autoimmune disease
- HCV is most common cause
- Systemic immune complex disease
- palpable purpura (leukocytoclastic vasculitis)
- arthralgias
- HSM
- LAD
- anemia
- sensorineural deficits
- glomerulonephritis
- Renal involvement:
- Nephrotic syndrome or nephritic syndrome
- Associated with severe hypocomplementemia
- MPGN type II most common
- +/- thrombotic microangiopathy
- electron microscopy: subendothelial immune complex deposits with a fibrillary or tubular structure in a fingerprint like pattern
34
Q
Lab method of protein electrophoresis
A
- Performed at pH 8.6 for serum, resulting in 5 bands: alpha1, alpha2, beta, and gamma
- bands are measured by densitometry
35
Q
Immunoelectrophoresis (IEP)
A
- No longer commonly used
- Patient serum placed in every other of a series of wells
- Remaining wells contain normal serum
- Gel undergoes EP
- Antiserum added to each trough
- Precipitation arcs form between antisera in the troughs and the electrophoresed proteins in the gel
- Interpretation depends on visual comparison of the arcs formed with patient serum
36
Q
Immunofixation electrophoresis
A
- Patient serum placed into 6 wellsin agarose gel
- Gel undergoes EP
- 5 different antisera applied to gel: anti IgG, IgA, IgM, kappa, and lambda
37
Q
Immunotyping
A
IT, immunosubtraction
- Often used in conjunction with capillary EP
- Serum sample incubated with different solid phase sepharose beads attached to antibodies against gamma, alpha, mu, kappa, or lambda
- supernatants undergo EP to determine which reagent resulted in removal of the abnormal spike
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