Acute Phase Reactants

Acute phase reactants is a physiological process that develops during local or systemic "inflammation", traumatic "tissue damage" (including post-surgical conditions), or "tumor growth". This reaction is less pronounced in many other situations, such as after extreme exercise, acute myocardial infarction or in the perinatal period.

Simply put, the acute phase reaction is caused by states where it occurs
 * to destroy cells,
 * for reversible cell damage and their subsequent repair,
 * to metabolically activate some cells (especially those involved in the immune response).

In the acute phase reaction, cells actively produce and release to the environment a whole spectrum of mediators and signalling molecules that induce rapid changes in the synthesis of various proteins in the liver (and to a lesser extent in other tissues). Proteins whose plasma concentrations vary significantly (by more than 25%) are referred to as "acute phase reactants" (PAFs);, APR's). The plasma concentration of some proteins increases (so-called "positive acute phase reactants"), others decreases ("negative acute phase reactants").

Significance of acute phase positive reactants
The set of acute phase proteins is quite diverse. Nevertheless, depending on the effect, most of them can be classified into one of the following groups:

Components of the immune response
 * Some acute phase reactants are directly involved in the elimination of agent, which has caused inflammation. Other proteins play a role in removing damaged cells or modulating the immune response. This includes e.g.
 * * C-reactive protein,
 * * complement components, in particular C3 and C4,
 * * tumor necrosis factor & alpha; (TNF- & alpha;),  interleukin 1 (IL-1) and  interleukin 6 (IL-6).


 * Protection against collateral tissue damage
 * During the acute phase, substances are mainly released from phagocytes and crumbling cells to destroy the nox that caused the inflammation and to "dissolve" the damaged tissue. They are mainly proteolytic enzymes and reactive oxygen species. The effect of these substances should be limited so that they act only where they have to act - ie so that the so-called "collateral tissue damage" is as small as possible. Acute phase reactants therefore find


 * Inhibitory proteases
 * &alpha;1-antitrypsin,
 * &alpha;1-antichymotrypsin,
 * &alpha;2-makroglobulin,


 * Proteins that reduce the production and availability of reactive oxygen species
 * These are not only scavengers reactive oxygen species in the true sense of the word, but also proteins that bind and stabilize transition metals and their complexes. This reduces the formation of ROS in the  Fenton reaction and similar processes. Is part of them
 * haptoglobin,
 * hemopexin,
 * ferritin,
 * ceruloplasmin.


 * Transport of waste products generated during inflammation
 * In addition to hemoglobin and hemopexin above, they probably belong here
 * serum amyloid A (SAA).


 * Coagulation factors and proteins involved in tissue regeneration, e.g..
 * fibrinogen.

The significance of some acute phase positive reactants remains "unknown", although they may be clinically important proteins (used as inflammatory parameters). For example, procalcitonin (PCT).

Rate of changes in the concentration of acute phase reactants
The plasma concentration of different acute phase reactants varies at different rates. According to the time from the beginning of the disease, during which it changes, we divide the acute phase reactants into three groups:

Early acute phase proteins
Are proteins with a very short biological half-life. Changes in their plasma concentrations are evident as early as 6-10 hours after the onset of the disease. The rise usually peaks during the second and third days. The main representatives are  'C-reactive protein (CRP)'  and  'serum amyloid A (SAA)' . More recently,  'procalcitonin (PCT)'  has been used in clinical practice.


 * C-reaktive protein


 * Procalcitonin

Acute phase proteins with a mean response time
are proteins whose concentration changes 12–36 hours after the onset of the disease and the maximum is reached at the end of the first week. These include & alpha; 1 -acid glycoprotein (orosomucoid),  & alpha; 1 -antitrypsin, haptoglobin] ] and [[fibrinogen.

Late acute phase proteins
are represented by complement components C3 and C4 and ceruloplasmin, in which changes do not develop until 48-72 hours after the onset of the disease. The increase in concentrations is less pronounced in comparison with the two previous groups of proteins and they do not reach a peak until 6-7 days.

Negative acute phase reactants
"Negative acute phase reactants" are proteins whose levels decrease during acute exercise. The main representatives are albumin, prealbumin and transferrin. They are less important than positive reactants for monitoring and evaluating the course of the load response. However, they are often used as a criterion for protein synthesis in the liver and as indicators of malnutrition.