Acute Inflammation – The Rapid Response System

Acute Inflammation – The Rapid Response System

The word inflammation originated in our language in the 1530’s and originally described redness or swelling in a body part. It has taken until recent years to understand the origins, process and consequences of this simple observation in passage of disease.

By design, inflammation is a complex process created by our immune system to rid the body of invading pathogens and to resolve trauma. In a healthy body this is often a rapid response defense and is over and done with quickly. The pathogen is killed and the body returns to quiet alert.

In the event of a strong pathogen such as causes Thyphoid or Cholera, the intensity of the reaction between the pathogen and the body defenses can overwhelm the immune system. But usually the healthy immune system wins. There may be a fever, inflammation, caused by the immune system to kill the pathogen, then recovery.

This is the part of inflammation that is most commonly understood both by medical and non-medical people.

The immediate reaction to infection, injury, and other acute events is a rapid acting responses. This is similar to calling 911 and finding all three emergency services arriving. It is more efficient to send in all the services than attempt to make judgments about what is happening from a distance.

The process begins with a series of chemical mediators, both in the surrounding fluids and in local cells. The pain response is by fast pain fibers sending signals which can trigger reflex response, such as pulling your hand back from a fire and sharp pain signals to the brain.

The first stage of response dilates the local blood vessels by way of Histamine and other chemical mediators. The cell junctions of the blood vessels open. The result is increased local levels of immune cell carried to the area by the incoming fluids. This can be seen as the beginning of swelling. White blood cells, the immune system’s shock troops, move to the area following chemicals released by bacteria and other microbes or by the body’s reaction to acute event itself.

White blood cells either engulf foreign matter, or kill invaders by enzyme release. They can, during this, cause tissue damage but that is the price of winning the battle. The acute response can escalate as is needed by the release of further immune mediators from our own cells in the area. Some of these are well known such as Prostaglandins and Cyclooxygenases, also called COX1 and COX2. It is these mediators which are targeted by NSAIDs and Cortisone medications. Also important are the cytokines, especially those designated as Interleukin 1 and Tumor Necrosis Factor-alpha. These can trigger a significant expansion of the acute immune response. There are over 90 cytokines and 20 different groups of chemical mediators involved in acute inflammation. The escalation continues until the issue is resolved or controlled.

The goal of this extraordinary process is one of four outcomes:

• Complete resolution. The pathogens are killed, the tissues healed and there is no further pain
• Abscess formation. Particularly with infection
• Healing by connective tissue replacement (fibrosis). This leaves scar tissue, after tissue destruction, when the inflammation occurs in tissues that do not regenerate.
• Progression to chronic inflammation due to the persistence of the pathogen or damage, or interference in the healing process.

Whether the event is caused by a wasp sting with its protein venom, a virus creating the common cold or an infected cut this is the