What is inflammation?

DR.

AIMEE DORDEVIC: Inflammation is essentially activity of the immune system. You might be most familiar with the classical inflammation. Classical inflammation includes the common symptoms such as redness, swelling, pain. If you’ve ever had a prickle or a cut on your hand, you might have seen these symptoms. And really what’s occurring there is that the damaged tissue is sending out signals to the immune system. Part of those signals cause physiological changes such as vasodilation. The vasodilation allows the immune cells entry into the site to perform tissue repair. That increased blood flow to the site of injury is what is causing the redness and swelling in that area.

This is known as acute localised inflammation and is a normal part of the body’s response to injury. With acute inflammation, we have resolution of inflammation. So with localised acute inflammation, the normal response once the immune cells have done their job and cleaned up the tissue damage or cleaned up any pathogens that may have entered, there’s resolution of this inflammation. And the swelling and the redness in those classical symptoms are alleviated. Another type of acute inflammation is when the immune cells are unable to contain the infection to that localised site. And the infection might be released into the blood stream. And we see a massive spike in inflammation or inflammatory molecules, which can actually be life threatening.

This is known as septic shock. It’s important to note that inflammation is a normal part of body functioning. The immune system is there to constantly perform surveillance of any external material that enters the body. The immune system isn’t only there to respond to tissue injury and infection. The immune cells are constantly circulating through our tissues to perform surveillance in case any damage is occurring, but also maintenance of the tissue as normal tissue turnover occurs. When we consume a meal, there are special immune cells that are located around the gastrointestinal tract.

And their role is to monitor the food or external material that enters our bodies to make sure that there’s nothing harmful there that’s going to cause damage to our tissues. So when we consume a meal, we see increased activity of immune cells while they’re monitoring that food for anything that might harm us. For a short period of time, we’ll see an increase in inflammatory molecules both within that area and also systemically. In a normal, healthy person, this inflammation will subside and settle back to baseline levels within a few hours after consuming the meal. So when inflammation doesn’t resolve, this results in chronic inflammation. There are a couple of different circumstances where chronic inflammation can occur.

An example is where the immune cells aren’t able to remove the infection from the body, such as in tuberculosis where we see ongoing infection that cannot be removed by the immune system. The granuloma grows within the lungs, and we have an upregulation of immune cells within that localised space over a long period of time. However, because it cannot actually effectively be removed, the immune system is constantly active and you see chronic inflammation in this localised area. Another type of chronic inflammation is something that’s called cold inflammation, or metabolic inflammation. We call it cold inflammation because we don’t see the classical symptoms of inflammation, such as redness, heat, and swelling.

We can observe increased levels of inflammatory signalling molecules at a subclinical level. And we see increased activity of immune cells in tissues throughout the body. And this isn’t necessarily caused by any specific tissue injury.