Plasma Proteins

Plasma Proteins

1. Functions

   • • Transport
     • (Albumin, prealbumin, globulins)
   • • Maintain plasma oncotic pressure
     • (Albumin)
   • • Defense
     • (Immunoglobulins and complement)
   • • Clotting and fibrinolysis
     • (Thrombin and plasmin)

2. Types of Plasma Proteins

   • Ceruloplasmin
     • Wilson’s disease:
       • Due to low plasma levels of ceruloplasmin
       • Copper is accumulated in the liver and brain
   • Haptoglobin
     • Plasma level decreases during hemolysis
   • B2–Microglobulin
     • May be a tumor marker for:
       • Leukemia, lymphomas, multiple myeloma
   • C-Reactive Protein (CRP)
     • A marker for ischemic heart disease
     • High plasma levels are found in many inflammatory conditions such as rheumatoid arthritis

3. Prealbumin (Transthyretin)

   • A transport protein for:
     • Thyroid hormones Retinol (vitamin A)
   • Lower levels found in:
     • liver disease, nephrotic syndrome, acute phase inflammatory response, malnutrition

4. Albumin

   • Hypoalbuminemia
     • Due to
       • Due to Decreased albumin synthesis (liver cirrhosis, malnutrition)
       • – Increased losses of albumin
     • Effects
       • • Edema
       • Reduced transport of drugs
       • Reduced protein-bound calcium – Total plasma calcium level drops
   • Decreases rapidly in injury, infection and surgery
   • Maintains oncotic pressure:
   • non-specific carrier
   • Hyperalbuminemia
     • The only cause of hyperalbuminemia is dehydration

5. a1-Antitrypsin

   • a1 -Antitrypsin Deficiency
     • Neonatal jaundice with evidence of cholestasis
     • Childhood liver cirrhosis
     • Pulmonary emphysema in young adults
   • An acute-phase protein that inhibits proteases
   • The most commonType is M type

6. a-Fetoprotein (AFP)

   • Elevated maternal AFP levels are associated with:
     • Neural tube defect (spina bifida), anencephaly
   • Decreased maternal AFP levels are associated with
     • Increased risk of Down syndrome
   • AFP is a tumor marker for:
     • Hepatoma and testicular cancer