Understanding Acute Phase Reactants in Immunity

1. Unit 1 Nature of the Immune System Part 3 Acute Phase Reactants Terry Kotrla, MS, MT(ASCP)BB

2. Immunity – Very Complex System

3. Soluble Factors • Many soluble tissue and serum substances help to suppress the grow of or kill microorganisms. • Interferons - family of proteins which are important non-specific defense mechanisms against viral infections. • Transferrin - Bacteria do not thrive well in serum that contains low levels of iron but high levels of transferrin. • Complement - a group of proteins that are essential for bacterial destruction and plays an important role in both non-specific and specific immune mechanisms.

4. Acute Phase Reactants (Proteins) • Defined-normal serum constituents that increase rapidly because of infection, injury, or trauma to tissues. • Acute-phase proteins are a class of proteins whose plasma concentrations increase or decrease in response to inflammation. • This response is called the acute-phase reaction . • In response to injury local inflammatory cells (neutrophils, granulocytes and macrophages) secrete a number of cytokines into the bloodstream, most notable of which are the interleukins. • The liver responds by producing a large number of acute-phase reactants.

5. C-Reactive Protein • Increases rapidly within 4-6 hours of infection or injury. • Returns to normal rapidly once condition subsides. • Used to monitor healing and has also increased in usefulness in diagnosing Myocardial Infarction.

6. Serum Amyloid A • Major protein secreted during the acute phase of inflammation. • Has several roles, including • Removes cholesterol from cholesterol-filled macrophages at site of injury – clean up. • recruitment of immune cells to inflammatory sites, and • Thought to play a role in cholesterol metabolism

7. Complement • A series of serum proteins involved in mediation of inflammation but also involved in • opsonization, • chemotaxis, and • cell lysis.

8. Alpha-1 Antitrypsin • Increases during acute inflammation. • Protects tissues from enzymes of inflammatory cells, especially elastase. • When the lungs do not have enough alpha-1 antitrypsin, elastase is free to destroy lung tissue. • As a result, the lungs lose some of their ability to expand and contract (elasticity). This leads to emphysema and sometimes makes breathing difficult.

9. Haptoglobin • Binds irreversibly to free hemoglobin to protect kidneys from damage and prevent loss of iron by urinary excretion. • Haptoglobin - hemoglobin complex removed by RES, mainly spleen. • Used to monitor hemolysis

10. Fibrinogen • A coagulation factor integral to clot formation which serves as a barrier to prevent spread of microorganisms further in the body. • Levels increase with tissue inflammation or tissue destruction. • Thought to play a key role in the inflammatory response and development of rheumatoid arthritis.

11. Ceruloplasmin • Principal copper transporting protein in plasma, plays a role in iron metabolism and histamine regulation. • Stimulates the immune system to fight infections, repair injured tissues and promote healing. • Depletion found in Wilson’s disease, causes the body to absorb and retain excessive amounts of copper. • Copper deposits in the liver, brain, kidneys, and the eyes. • The deposits of copper cause tissue damage, necrosis (death of the tissues), and scarring, which causes decreased functioning of the organs affected. • Liver failure and damage to the central nervous system (brain, spinal cord) are the most predominant, and the most dangerous, effects of the disorder.

12. References • http://www.horton.ednet.ns.ca/staff/Selig/isu/Immunity/Innate.htm • http://www.metacafe.com/tags/neutrophil/most_popular/