This document discusses plasma proteins and their functions. Some key points: - Plasma is the liquid component of blood that remains after red and white blood cells are removed by centrifugation. It makes up 55-60% of total blood volume. - Serum is similar to plasma but lacks coagulation factors as it is produced when blood is allowed to clot. - The main plasma proteins are albumin, globulins, and fibrinogen. Albumin maintains osmotic pressure while globulins are involved in transport and immunity. - Electrophoresis and immunoelectrophoresis can separate plasma proteins based on their electrical charge and antigenic properties. Specific acute phase proteins increase during inflammation.

2. Plasma Proteins
Total blood volume is about 4.5 to 5 liters in adult human
being.
If blood is mixed with an anticoagulant and centrifuged, the
cell components (RBC & WBC) are precipitated. The
supernatant is called plasma. About 55-60% of blood is made
up of plasma.
If blood is withdrawn without anticoagulant and allowed to
clot, after about 2 hrs. Liquid portion is separated from the
clot. This defibrinated plasma is called serum, which lacks
coagulation factors including prothrombi and fibrinogen.

3. Centrifuged Blood Sample
Add anticoagulants
(heparin, potassium
oxalate)

4. Separation of Components
Plasma = Less Dense
RBCs
More Dense
Platelets / WBCs

5. Plasma vs. serum
Plasma is the liquid,
cell-free part of
blood, that has
been treated with
anti-coagulants.
Anticoagulated
Serum is the liquid part
of blood AFTER
coagulation, therfore
devoid of clotting
factors as fibrinogen.
serum= plasma - fibrinogen
Clotted

6. Components of Plasma
Blood plasma Consists of:
Water 90%
Plasma Proteins 6-8 %
Electrolytes (Na+ & Cl-) 1%
Other components:
Nutrients (e.g. Glucose and amino acids)
Hormones (e.g. Cortisol, thyroxine)
Wastes (e.g. Urea)
Blood gases (e.g. CO2, O2)

8. A large number of dissolved proteins of the plasma
includes :-simple proteins, conjugated proteins
carry out a number of different functions.
Plasma proteins

9. General characteristics of plasma proteins
1. They are synthesized in liver except
immunoglobulin.
2. Almost all plasma proteins are glycoproteins.
3. Many plasma proteins exhibit polymorphism such
as α1-antitrypsin, transferrin, haptoglobin.
4. Each plasma protein has a characteristic half-life in
the circulation.
5. Acute Phase Proteins, APP

10. Total protein content of normal plasma is 6 to 8 g/100ml.
The plasma proteins consist of :-
albumin(3.5 to 5g/dl),
globulins(2.5 to 3.5g/dl) and
fibrinogen(200 to 400mg/dl).
The albumin: globulin ratio is usually between 1.2:1 to 1.5:1.
Almost all plasma proteins, except immunoglobulins are
synthesized in liver. Plasma protein are generally synthesized
on membrane- bound polyribosomes. Most plasma proteins
are glycoproteins.

11. Total Protein
 One of the more common measurement in clinical lab.
 Includes albumin(60%) & globulins(40%)
 Total protein may be altered by changes in fluid
balance:- dehydration , excessive sweating, diarrhea,
vomiting, salt-losing syndromes.
 conversely hemodilution causes decrease serum
protein as in administration of volume expanders
(dextran), pregnancy & salt retention syndromes

12. In laboratory, separation can be done by salts:-
fibrinogen is precipitated by 10% and globulins by 22%
concentration of sodium sulfate.
Ammonium sulfate will precipitate globulins at half
saturation and albumin at full saturation.
In clinical laboratory, total proteins in serum or plasma
of patients are estimated by Biuret method.
Albumin is quantitated by Bromo cresol green
method, in which the dye is preferentially bound with
albumin, and color is estimated colorimetrically.

13. Separation
1. Electrophoresis 2. Ultra-
centrifuge
A/G=1.5~2.5

14. Electrophoresis
Electrophoresis:- movement of charged particles
through an electrolyte when subjected to an electric
field.
The positively charged particles (cations) move to
cathode and negatively charged ones (anions) to
anode.

15. Normal Patterns and Interpretation
 In agar gel electrophoresis, normal serum is separated into 5
bands.
Albumin : 55-65%
Alpha-1 globulin : 2-4%
Alpha-2 globulin : 6-12%
Beta globulin : 8-12%
Gamma globulin : 12-22%
 Albumin has the maximum and gamma globulin has the
minimum mobility in the electrical field.
 Gamma globulins contain the antibodies (immunoglobulin).
Most of the alpha-1 fraction is made up of alpha-1 antitrypsin.
Alpha-2 band is mainly made up by alpha-2 macroglobulin. Beta
fraction contains density lipoproteins.

16. The main component of the globulins
a1-AT
Haptoglobin
a2--macroglobulin
HDL
Transferrin
LDL, C3
Immunolobulins
Fibrinogen, CRP
a1 a2albumin b1 b2 g

17. Plasma proteins

20. Albumin
Albumin (69 kDa), single polypeptide chain having
585 a.a. with 17 disulfide bonds, is the most abundant
protein (60%) in the blood plasma. (3.5-5.0 g/dl)
Synthesis of albumin:
Synthesized as a preproprotein
preproalbumin proalbuminsignal
peptide
hexapeptide albumin+ +furin
signal
peptidase

21. Liver produced about 12g albumin per day which
represent 25% of total hepatic protein synthesis
and 50% of secreted protein.
half-life: 20 days
For this reason, measurement of serum albumin
concentration is used to assays liver function test.

22. Structure
1. Shape: ellipsoid.
2. Charge: pI=4.7
3. Domain: three major domains.

23. Functions of Albumin
1. Maintain of osmotic pressure
 Colloid osmotic pressure, is a form of osmotic
pressure exerted by proteins in blood plasma that
usually tends to pull water into the circulatory system.
 Because large plasma proteins cannot easily cross through
the capillary walls.
 In conditions where plasma proteins are reduced,
e.g. from being lost in the urine (proteinuria) or from
malnutrition, there will be a reduction in osmotic pressure,
leading to enhanced fluid retention in tissue spaces
(edema).

24.  According to starling’s hypothesis, at the capillary end,
the blood pressure or hydrostatic pressure expels water
out , and effective osmotic pressure takes water into the
vascular compartment.
 At arterial end of the capillary, BP is 35 mm Hg and EOP
is 25 mm; thus water is expelled by a pressure of 10
mmHg.
 At the venous end of the capillary, EOP is 25mm and BP
is 15 mm, and therefore water is imbibed with a pressure
of 10 mm.
 Thus, the number of water molecules escaping out at
arterial side will be exactly equal to those returned at the
venous side and therefore blood volume remains the
same.

25.  If protein concentration in serum is reduced, the EOP
is correspondingly decreased. Then return of water
into blood vessels is diminished, leading to
accumulation of water in tissues. This is called edema.
 Edema is seen in conditions where albumin level in
blood is less than 2g/dl

26. Colloid osmotic pressure
Low albumin, causing edema.

28. 2. Transport:- It can bind and transport many diverse
molecules and serve as low-specificity transport
protein, which include:
a. Metal ions: such as calcium and copper.
b. Free fatty acid: albumin binds to free fatty acid released by
adipose tissue and facilitates their transfer to other tissue.
c. Bilirubin: this protects from the toxic side effects of
unconjugated bilirubin.
d. Bile acid: albumin carries the bile acids that are recycle
from the intestine to the liver in the hepatic portal vein.
e. Hormones: such as thyroid hormones and the steroid
hormones.

29. 3.Buffering action
All protein have buffering capacity. Beacuse of its high
concentration in blood, albumin has maximum
buffering capacity. Albumin has a total of 16 histidine
residues which contribute to this buffering action.
4.Nutritional function
All tissue cells can take up albumin by pinocytosis. It is
then broken down to amino acid level. So albumin may
be considered as the transport form of essential amino
acids from liver to extrahepatic cells. Human albumin is
clinically useful in treatment of liver diseases,
hemorrhage, shock and burns.

30. 5.Helps in maintaining viscosity of blood
6.Provides stability of blood
7.Immune function…

31. Clinical aspects
1. Albumin binds different drugs and
strongly affects the pharmacokinetics
of these drugs.
For example, sulfonamides can cause
the release of unconjugated
bilirubin from albumin by
competitive binding. If given to
infants, sulfonamides may lead to
kernicterus.
2. In cases of liver disease or starvation,
albumin synthesis decreases.
This lead to edema.

32. Clinical aspects
3. Hypoalbuminemia
Malnutrition
Cirrhosis of liver
Nephrotic Syndrome
Albuminuria
Protein lossing enteropathy
Analbuminemia
5. Albumin is therapeutically useful for the treatment
of burns and hemorrhage.

33. A trp rich tetrameric nonglycosylated protein named
for its anodal migration relative to albumin on
protein electrophoresis. Or Migrates faster than
albumin in electrophoresis
A transport protein for:
Thyroid hormones
Retinol (vitamin A)
Separated by immunoelectrophoresis
Prealbumin (Transthyretin)

34.  RBP is a small monomeric(21 KD) transport protein for all trans retinol.
requires zinc for synthesis.
 Forms complex with transthyretin in plasma to prevent it from being
filtered by renal glomeruli.
 Reference interval:
 RBP=3-6mg/dl
 TTR=20-40mg/dl or 195-358mg/L

35.  Transthyretin levels are used as indicator of protein status because of
short half life, high tryptophan content, high proportion of essential to
non essential amino acid and small pool size.
 Increased level :chronic renal disease ,corticosteroid or NSAID therapy.
 Decreased levels: liver disease, protein malnutrition, APR & Zinc
deficiency.

36. α1–Antitrypsin
α1–Antiproteinase(α1–AT or AAT) or protease
inhibitor
Termed as (SERPIN)
It (52 kDa) is a glycoprotein with 394 aa.
It is a major constituent of α1 globulin fraction of plasma
protein.
normal concentration about 76-189 mg/dl.
Also found in tears, lymph, bile, semen & aminiotic fluids.

37.  Synthesized primarily by hepatic parenchymal cells.
 Catabolism also occurs in hepatic parenchymal cells by
two ways:-
AAT1 protease complex are removed by the serpin
enzymes complex receptors.
Desialylated AAT is removed by hepatic asialoglycoprotein
receptors.
 AAT function mainly to inhibit non-trpsin proteinase,
especially elastase & collagenase in tissues & body fluids.
 These enzymes are released by leucocytes & macrophages

38. Clinical significance
1. Emphysema: used to
represent the abnormal
distension of lungs.
2. About 5% is due to the
deficiency of α1–AT.
3. This is associated with lung
infection and increase the
activity of macrophage to
release elastase that damage
lungs tissue.

39. 2.α1–antitrypsin deficiency
liver disease- due to
mutant α1 –antitrypsin
accumulates and aggregates
to form polymers, by
unknown mechanism, cause
liver damage followed by
accumulation of collagen
resulting in fibrosis
(cirrhosis).

40.  AAT conc. Increase by acute phase response & by
estrogens.
 AAT conc. Secondarily low in respiratory distress
syndrome, severe pancreatitis & protein losing
disorders.
 Smoking can cause oxidation of Met358 to
methionine sulfoxide and inactivate α1–AT.

41. α1- Acid Glycoprotein or Orosomucoid
Contains high concentration of carbohydrate with a
large no. of sialic acid residues. Thus it has a very high
net negative charge and is very soluble in water.
Functions
α1-acid glycoprotein is classified as one of the
lipocolin proteins that bound lipophilic substances.
Each molecule of AAG contains 181 a.a and total
molecular mass 40kDa.

42. Clinical Significance
 α1- Acid glycoprotein concentration increase in the
acute phase reactants, especially in GI inflammatory
disease and malignant neoplasms.
 Concentration are increased by corticosteroids.
 Estrogen(e.g. From pregnancy or oral contraception)
decrease the synthesis of AAG.
 AAG also decrease in nephrotic syndrome.

43. Retinol Binding Protein
 Retinol binding protein is a small 21kDa, monomeric
transport protein for all-trans-retinol, the physiologically
active, alcoholic form of vit. A.
 Zinc is required for the synthesis.
Clinical significance
 Decreased concentration of retinol binding protein are seen
primarily with liver disease, protein malnutrition and acute
phase reactant.
 Zinc deficiency is characterized by low serum concentration
of both retinol binding protein and vit. A.

44. α2 –Macroglobulin (α2 –MG)
It (720 kDa) is a glycoprotein with 4 identical
subunits, a major constituent of α2 fraction.
It is a major plasma protease inhibitor and can
combine and inhibit many protease.
It can bind numerous growth factors, hormones
cytokines. includes PDGF, IL6, insulin, TNF-α and
TGFβ1 & β2 and target them to particular cells to
affect on cell growth or function.

45. Clinical significance
 Normal range- 125-215 mg/dl
 α2 -MG levels are increased in nephrotic
syndrome
a condition where in the kidneys start to leak out
some of the smaller blood proteins. Because of its
size, α2 -MG is retained in the bloodstream.
 This increase has little adverse effect on the
health, but is used as a diagnostic clue.
nephrotic syndromenormal

46. Haptoglobin (Hp)
It (90 kDa) is a glycoprotein.
It can bind with the free hemoglobin released by red
cell destruction, thus conserving body iron &
preventing renal filtration of potentially nephrotoxic
Hb.
Hp-Hb(155 kDa) cannot pass through glomeruli of
kidney while free Hb(65kDa) can and Hp prevent the
loss of free Hb into urine.

47. Hp can bind HbA, F, S and D but not types that
lacks an α chain.
Total plasma binding capacity of Hp is approx. 3g of
Hb.
The kidney can process up to 5g of Hb/day, above
this level, free Hb appears in the urine.
Low levels of plasma concentration of Hp can
diagnose hemolytic anemia.
t1/2 of Hp: 5 day, Hp-Hb: 90 min.

48.  Three distinct phenotypes of Hp have been
identified by electrophoresis & designated as
Hp1-1, Hp1-2 & Hp2-2
 These are not associated with disease.

49. Clinical Significance
 Hp concentration increase by corticosteroid hormones.
 Hp, like ceruloplasmin is a weak and late reacting acute
phase protein.
 Hp concentration elevated in nephrotic syndrome &
biliary obstruction
 Hp is decreased in diseases associated with intravascular
hemolysis, including haemolytic anemias,
hemoglobinopathies, burns, malaria etc.
 In severe acute hemolysis, Hp may be totally depleted
within 6 to 12 hours, requiring upto 1 week to return to
normal.

50. Ceruloplasmin(CER)
It (160 kDa) is a blue-coloured, copper-containing α2
fraction. It contains 6-8 copper atoms per molecule.
after the formation of peptide part copper is added by
an intracellular ATPase and carbohydrate side chain are
added to make it a glycoprotein.
CER is mainly synthesized by the hepatic parenchymal
cells and a small portion by lymphocytes &
macrophages.

51.  The normal plasma half life of Cp 4-5 days.
 CEP is also called ferroxidase, an enzyme which helps in the
incorporation of iron into transferrin.
 It can carry 90% of plasma copper tightly so that copper is not
readily exchangeable. It pocesses copper-dependent oxidase
activity.
 The majority of plasma Cu is bound to CER, the remainder is
bound to albumin & transcuprin.
 Albumin carries the other 10% , which is the major supplier of
copper to tissue.

52. Clinical significance
Low level of ceruloplasmin is associated with Wilson’s
disease (hepatolenticular degeneration), malnutrition,
nephrosis and cirrhosis.
Wilson's disease is an inherited disorder in which there
is too much copper in the body's tissues. The excess
copper damages the liver and nervous system .
Treatment: penicillamine is the first treatment used.
This binds copper (chelation) and leads to excretion of
copper in the urine.

53.  Wilson Disease:- basic defect in ATP7B gene in liver
cells. An Autosomal recessive disorder.
 Cu absorption is normal whereas excretion into bile is
defective.
 As a result Cu is accumulated into various tissues –liver,
brain, cornea, & kidneys.
 Clinical manifestations- kayser-fleisher corneal rings,
hepatitis, cirrhosis, intellectual deterioration, behavioral &
personality changes, tremor & gait disturbance.

54.  Menke’s kinky hair syndrome
(trichopoliodystrophy):- X-linked disorder, affects only
male children. Mutation in ATP7A gene. Feature includes
 pili torti (kinky hair), retarded growth, hypotonia,
seizures, failure to thrive, cerebral degeneration, cardiac
rupture , bone & joint deformities.
 Serum Cu & Ceruloplasmin is low.

55. Transferrin(siderophilin) (Tf)
It (76 kDa) is a glycoprotein, part of β fraction,
containing two iron –binding sites on a single
polypeptide chain.
Transferrin binds ferric iron in a reversible ionic bond
accompanied by the uptake of one bicarbonate anion
per atom of iron.
It can transport iron in plasma as ferric ions (Fe3+) and
protect the body against the toxic effects of free iron.

56.  Specific iron binding protein, half life 7-10 days and is
used as a better index of protein turnover than
albumin.
 Increase in IDA & pregnancy
 Decrease in PEM, cirrhosis of liver, nephrotic
syndrome etc.

57. The acute phase reactants (APRs) are a group of
proteins whose plasma conc. changes in response to a
variety of inflammatory states including infections,
surgery, trauma, MI, malignancy, the birth process and
any condition associated with tissue necrosis.
Include C-reactive protein, α1-acid glycoprotein,
fibrinogen, haptoglobin, α1-antitrypsin, albumin and
transferrin.
Acute Phase Proteins, APP

58. Types of APRs
Negative:
albumin
transferrin
antithrombin
transcortin
retinol binding
protein
Positive:
C-reactive protein: ~1000-
fold increase!
a1-antitrypsin
α1-antichymotrypsin
Ceruloplasmin
Hemopexin
fibrinogen
haptoglobin (HP)
C3, C4
Serum amyloid A (SAA)

59. C-reactive protein, CRP
 A major component of acute phase protein.
 CRP was identified in 1930 as a substance in the sera of
patients with pneumococcal pneumonia that could bind to C-
polysaccharide isolated from streptococcus pneumoniae.
 Estimation of CRP in serum is important for the evaluation of
acute phase response.
 CRP rises up to 50,000-fold in acute inflammation, such as
infection. It rises above normal limits within 6 hours, and
peaks at 48 hours.
 Half life:- 19hours
 Normal in Plasma:- <0.8 mg/dl

60. Functions
 Initiation of opsonization & phagocytosis and
activation of complement, neutrophils and monocyte
macrophages.
 Collectively these properties imply an imp. Role for
CRP in the recoginition of microbial organisms and as
an immunomodulatory in host defence.

61. Fibrinogen
 A soluble glycoprotein, also called as clotting factor I as it
takes part in coagulation of blood and it is a precursor of
fibrin, substance required for clotting.
 Activated by thrombin.
 Fibrnogen is converted to clot (fibrin), by cleaving of
Arg-Gly peptide bond of fibrinogen
 Synthesised in liver, also a APR
 Normal value:-200-400mg/dl

62. Immunoglobulin(Ig)/antibody(Ab):
Glycoprotein molecules that are produced by plasma cells in
response to an immunogen and which function as antibodies,
mostly associated with γ fraction.
But γ-globulin and Ig are not synonymous.
• Ig is a functional term
• γ-globulin is physical term.

63. 1.IgG - γ heavy chains
2.IgM - µ heavy chains
•pentamer
3.IgA - α heavy chains
•dimer
4.IgD - δ heavy chains
5.IgE - ε heavy chains
Immunoglobulin Classes
dimer pentamermonomer

64. Thank you

65. Abnormal Patterns In Clinical Diseases
 Chronic infections:- the gamma globulins are increased, but the
increase is smooth and widebased.
 Multiple myeloma:- in para-proteinemias, a sharp spike is noted and
is termed as M-band. This is due to monoclonal origin of
immunoglobulins in mutiple myeloma.
 Fibrinogen:- instead of serum, if plasma is used for electrophoresis,
the fibrinogen will form a prominent band in the gamma region,
which may be confused with the M-band.
 Primary immune deficiency:- the gamma globulin fraction is
reduced.
 Nephrotic syndrome:- all proteins except very big molecules are lost
through urine, and so alpha-2 fraction(containing macroglobulin) will
be very prominent.
 Cirrhosis of liver:- albumin synthesis by liver is decreased, with a
compensatory excess synthesis of globulins by reticuloendothelial
system. So albumin band will be thin, with a wide beta fraction;