Quiz 4: Proteins and the Renal System

Question 1

Proteins in Urine

Answer 1

• Albumin (mw 66 000) is too large for reabsorption.

* Proteins with mw 15,000 to about 40,000 pass freely into the urine when they are not conserved through reabsorption.

Question 2

Proteinuria

Answer 2

• Albumin in urine suggests defects in glomerular filtration. (RI = 20 - 250 mg/day)
- Detected via dipstick (albumin binds to pad)
- Confirmed with: Test for renal tubular function, Immunoassay (ELISA, EIA)
Tubular Proteinuria
• Low mw (15k - 40k) proteins in the urine reflect defects in reabsorption

Question 3

Globulin Detecting Methods

Answer 3

• Alpha1 antitrypsin: acute phase protein that neutralizes trypsin proteins that can damage tissues.
- Important genetic deficiency leads to severe lung disease.
• Alpha1 fetoprotein: protective in the fetus and an important tumor marker in adults.

Question 4

Globulin Proteins

Answer 4

• Alpha1 acid glycoprotein (orosomucoid)
• Alpha2 macroglobulin
• Beta2 microglobulin
• Complement
• Fibrinogen
• C-Reactive Protein
• 
•

Question 5

Alpha1 acid glycoprotein (orosomucoid)

Answer 5

Increased during inflammation

Question 6

Alpha2 macroglobulin

Answer 6

Increases in serum in kidney disease due to its large size.

Question 7

Beta2 microglobulin

Answer 7

Small size, freely cleared by renal glomerulus and 99% reabsorbed
Sensitive indicator of kidney damage when levels in serum are elevated

Question 8

Complement

Answer 8

Group of proteins involved in the immune response (see immunoglobulins)

Question 9

Fibrinogen

Answer 9

Involved in clot formation, found between beta and gamma bands on electrophoresis of plasma, not found in serum.

Question 10

C-Reactive Protein

Answer 10

Inflammatory response protein
• CRP binds to bacteria (opsonization) which promotes binding of complement which leads to phagocytosis of bacteria.
• One of the first acute phase proteins to rise in infections and immune response diseases (RA, viral infections etc)

Question 11

Bence Jones Proteins, Detection

Answer 11

• Light chains of Ab in urine, found in multiple myeloma patients
• Methods for detection: electrophoresis and/or specific immunoassays for light chains.

Question 12

Paraproteins (Myeloma Detection)

Answer 12

• Abnormal light chains

* Lower mw of light chains compared to full immunoglobulins results in their secretion into the urine.

Question 13

Ab Breakdown (Papain and Pepsin)

Answer 13

1) Reduce and Pepsin: Fab’
2) Papain: Fab and Fc
3) Pepsin: F(ab’)2 and pFc’

Question 14

Immunoglobulin Detection

Answer 14

• Electrophoresis (including various forms of Immunoelectrophoresis)
• nephelometric
• turbidimetric
• EIA
• RID

Question 15

Locations of Immunoglobulins in the Body

Answer 15

IgG: major function is neutralization of toxins like virus, bacteria etc
IgM: first early response to an antigen.
IgE: trace amounts in serum, mostly from Mast Cells’ histamine release during immune response
IgA: present in secretions
IgD: auto-regulation

Question 16

Conditions Causing Immunoglobulin Deficiency

Answer 16

Defective Synthesis
Lymphoid malignancies
Toxic reaction to drugs
Renal failure Diabetes

Question 17

Conditions Causing Immunoglobulin Increase

Answer 17

• B-lymphocyte lymphomas
• Lymphocytic leukemia
• Waldenstrom’s macroglobulinemia
• Multiple Myeloma (neoplasm of plasma cells)
  Polyclonal: Normal response to infections
  Monoclonal (Paraproteins):
  Single clone of plasma cells produce immunoglobulin of identical structure.
  Plasma cells also may produce increased amounts of light chains (lambda chains) and rarely heavy chains (kappa chains)

Question 18

Electrophoretic Spread of Globulins

Answer 18

(-) Gamma Globulins - Beta Globulins - Alpha Globulins - Albumin (+)
Moving toward the Anode

Question 19

Nephrotic syndrome

Answer 19

In which albumin is lost, giving low Alb staining and alpha2/ beta bands in SEP are increased due to retention of proteins like alpha2 macroglobulin.

Question 20

Acute-Phase Reactant Pattern in SEP

Answer 20

Seen when albumin is decreased and alpha and beta bands are increased. CRP found in beta band.

Question 21

Liver Disease in SEP

Answer 21

Shows decreased albumin, and increase in gamma globulin band.

Question 22

High Resolution Electrophoresis (HRE)

Answer 22

Increases the number of bands from 5 to 12. Uses modified buffer, agarose, temperature control and high voltages.

Question 23

Capillary Electrophoresis (CE)

Answer 23

Separates proteins inside thin capillaries (< 1 micron) under high voltage (> 20 000 vdc).

Question 24

24hr Urine Testing

Answer 24

Quantitatively tested using Sulfsalicyclic Acid, Trichloroacetic Acid, Benzethonium chloride and Coomassie Brilliant Blue

Question 25

Microalbuminuria

Answer 25

Quantity of albumin is greater than normal but not detectable by urine dipstick, usually precedes nephropathy