Plasma Proteins

Which organs and cells are primarily responsible for producing most plasma proteins?

Hepatocytes in the liver

What are the main types/classes of proteins found in plasma?

Albumin and globulins (immunoglobulins, positive acute phase proteins, coagulation proteins, and complement proteins)

What is the major difference in composition between serum and plasma?

Plasma contains clotting factors and fibrinogen, while serum lacks fibrinogen and most coagulation proteins.

Define serum.

The liquid portion of blood after coagulation, lacking fibrinogen and other clotting factors.

Define plasma.

The liquid portion of blood with clotting factors present, obtained from anticoagulated blood.

What are the major functions of albumin?

Maintains plasma colloidal osmotic pressure, transports small molecules, buffers pH, provides amino acids.

What are the major functions of globulins?

Transport proteins, immune defense (immunoglobulins), inflammation response (acute phase proteins), coagulation, complement.

What are the major functions of immunoglobulins?

Provide specific immune defense by recognizing and neutralizing antigens.

What are the major functions of positive acute phase proteins?

Increase in respond to inflammation, infection, or tissue injury; examples include haptoglobin, CRP, serum amyloid A.

What are the major functions of coagulation proteins?

Promote blood clotting to prevent hemorrhage.

What are the major functions of complement proteins?

Mediate inflammation, opsonization, and cell lysis

What are the general consequences of a major albumin deficiency and impaired lymphatic system?

Edema/Effusion due to reduced plasma oncotic pressure

What are the general consequences of a major globulin deficiency?

Impaired immune response, increased susceptibility to infections, reduced transport of lipids and metals.

What is the main contributor to plasma colloidal osmotic (oncotic) pressure?

Albumin.

Which two types of globulins generally increase during an established inflammatory disease?

Immunoglobulins and positive acute phase proteins.

Arrange IgM, IgG, and albumin in order from largest to smallest.

IgM > IgG > albumin.

What is the approximate half-life of plasma albumin in common domestic mammals?

1-3 weeks.

Name major positive acute phase proteins.

Haptoglobin, serum amyloid A (SAA), C-reactive protein (CRP), and fibrinogen.

What are the major clinical tests for plasma proteins?

Total Protein, Refractometric, Heat Precipitated Fibrinogen, Serum Protein electrophorese (SPE)

How is the serum concentration of globulins determined?

Globulins = Total protein − Albumin.

How do artifactual increases or decreases in total protein or albumin affect calculated globulin concentration?

They cause falsely high or low globulin values.

Which assessment of total protein concentration is more reliable: chemical biuret method or refractometry, and why?

Chemical biuret method; refractometry can be affected by lipemia, hemolysis, or hyperglycemia.

How do IgG and albumin appear differently on a serum electrophoresis gel?

Albumin forms a large, sharp peak; IgG forms a smaller, broader peak in the gamma region.

In which region of serum protein electrophoresis does IgG migrate?

The gamma (γ) region.

Do plasma proteins cause turbidity in blood?

No.

Why can proteins have an overall charge?

Proteins' R-groups have different charges, giving the protein an overall net charge.

What percentage of plasma proteins does fibrinogen comprise, and what is its function?

~5%; critical for coagulation, inflammation, and wound healing.

Which cells produce immunoglobulins?

Plasma cells and B-lymphocytes

What is colostrum's role in protein transfer?

Passive transfer maternal immunoglobulins (mainly IgG) and plasma proteins to neonates

What are negative acute phase proteins?

Proteins that decrease with acute inflammation, e.g., albumin and transferrin.

What is albumin's approximate size?

~60 kDa, smaller than globulins.

What percentage of plasma oncotic pressure is maintained by albumin?

75-80%.

Where are globulins produced?

Plasma cells/B-lymphocytes (immunoglobulins) and hepatocytes (other globulins).

Name the three types of globulins and their sources.

Alpha: liver; Beta: mainly liver, some lymphoid tissue; Gamma: lymphoid tissue

How do neonates obtain immunoglobulins?

Passive transfer from colostrum (mainly IgG); later produce their own.

What drives fluid out of blood vessels?

Hydraulic (blood) pressure.

What draws fluid back into blood vessels?

Oncotic (colloid osmotic) pressure, primarily driven by albumin.

What happens with hypoproteinemia (low albumin)?

Decreased oncotic pressure → increased net outflow → edema or effusion if lymphatic drainage is impaired.

How is total plasma protein measured?

Total Protein (TP) via biochemical analyzer in plasma.

How is albumin measured clinically?

Serum or plasma, species-specific, using clinical chemistry profile.

How is globulin concentration determined clinically?

Globulin = Total Protein − Albumin.

What is the refractometric method?

Measures total solute concentration in plasma; light refraction proportional to % total solids.

How is fibrinogen measured in large animals?

Heat precipitation method: plasma heated at 56°C for 3 min; fibrinogen denatures and is measured.

What is serum protein electrophoresis (SPE)?

Separates proteins by size and charge to identify clinical abnormalities