How To: Understand the Process of Inflammation

In each day of our life, we see inflammation. We see it during sore throats and abscess formations in our bodies, and even slight tooth pain is a form of inflammation. Sometimes it's good when it fights to protect us from invading organisms, but sometimes it becomes bad when it occurs in inappropriate ways, like acne.

What we are going to learn today is the general rules about inflammation and the immune system. With time, our knowledge will grow more and more in that field. To learn more about the immune system, read How to Understand the Way Our Immune System Fights Enemies Like a Modern Army.

The process of inflammation that happens secondarily to infection is like this:

Step 1 Invasion of the tissue by an organism

The organisms invade the healthy tissue and infect its cells. The organisms cause damage to the tissue that results in the release of chemical substances that attract the local immune cells to the site of inflammation.

Step 2 Activation of local histiocytes in the tissues

The first cells of the immune system to respond to the infections are the tissue histiocytes (macrophages). 

They start to fight back the invading organisms until the tactical support comes from the white blood cells in the blood stream.

Step 3 Biochemical messages and body response

When the fight between the local immune cells and the invading organisms reach its height, they release secret chemical substances that leads to widening of the local blood vessels to bring more blood to the site of infection.

The wide blood vessels allow the white blood cells to reach the site of inflammation to give support to the local immune cells. 

The increased blood flow to the site of inflammation leads to characteristic signs; swelling, redness, warmness and pain.

In this picture, we see the mouth of a patient with a sore throat.

Step 4 Dendritic cells; better espionage, better response

These cells bring information and samples from the invading organisms. They process them and send the information in the form of chemical signals to the upcoming immune support from the blood [white blood cells]. 

This is very important because if these cells detected that the invading organism is virus, they would send a signal to the CD-8 T-Lymphocytes to come to fight, as they are specialized in viral attacks.

If they detected that the invading organism is pyogenic bacteria, they would send signals to the neutrophils to come to the fight, because they are specialized in bacterial attacks. 

Another function of these cells is to instruct certain types of cells called memory cells, which is responsible for long lasting immunity after attacks by some virus, e.g. measles and mumps.

Step 5 The arrival of the main fighting force

The rescue cells coming from the tissue under attack reach the white blood cells. They arrive in forces to give tactical support against the invading organisms.

The arriving forces may by be neutrophils if it is bacterial attack, or they may be CD-8 T-Lymphocytes if it's viral attack. 

These cells start to give tactical support to the fighting local immune cells leading to elimination of the invading organism, either by phagocytosis [eating up the enemy] or cell mediated cytotoxicity [injecting lethal chemicals into the invading enemy].

Step 6 Return to normal

After elimination of the invading organism, the fighting white blood cells start to get out of the site of the infection and return back to the blood stream. 

Dead cells are taken away by phagocytosis.

Fibroblasts [tissue engineers] start to repair the damage at the site of inflammation. After a period of time, the site returns to normal like it was before the inflammation.

Conclusion

The response of the immune system to inflammation is step-by-step. Each step is necessary for better functioning of the immune system.

In the next article, we will learn how physicians support the body during the inflammations against invading organisms.

The short video below shows how the attraction of white blood cells happens, and how they perform phagocytosis.