When your body fights off an infection, you develop a fever. If you have arthritis, your joints will hurt. If a bee stings your hand, your hand will swell up and become stiff. These are all manifestations of inflammation occurring in the body.
We are two immunologists who study how the immune system reacts during infections, vaccination and autoimmune diseases where the body starts attacking itself.
While inflammation is commonly associated with the pain of an injury or the many diseases it can cause, it is an important part of the normal immune response. The problems arise when this normally helpful function overreacts or overstays its welcome.
What is inflammation?
Generally speaking, the term inflammation refers to all activities of the immune system that occur where the body is trying to fight off potential or real infections, clear toxic molecules or recover from physical injury. There are five classic physical signs of acute inflammation: heat, pain, redness, swelling and loss of function. Low-grade inflammation might not even produce noticeable symptoms, but the underlying cellular process is the same.
Take a bee sting, for example. The immune system is like a military unit with a wide range of tools in its arsenal. After sensing the toxins, bacteria and physical damage from the sting, the immune system deploys various types of immune cells to the site of the sting. These include T cells, B cells, macrophages and neutrophils, among other cells.
The B cells produce antibodies. Those antibodies can kill any bacteria in the wound and neutralize toxins from the sting. Macrophages and neutrophils engulf bacteria and destroy them. T cells don’t produce antibodies, but kill any virus-infected cell to prevent viral spread.
Additionally, these immune cells produce hundreds of types of molecules called cytokines – otherwise known as mediators – that help fight threats and repair harm to the body. But just like in a military attack, inflammation comes with collateral damage.