Understanding the macrophage role in immune response

Published On: 21 March 2019By

As a type of white blood cell that attack, eat, and destroy bacteria, macrophages play a big role in your immune system’s response to invaders. Additionally, they help your immune system adapt so that it can tackle viruses at a later date. Learning more about macrophages’ role in immune response can help you understand areas of medicine such as infections and vaccinations.

What are macrophages?

There are lots of macrophages present in your blood, and they all stem from a larger white blood cell called a monocyte. They can migrate from your circulatory system to the tissues where they’re needed most. Several types of macrophages perform specific roles. For example, an alveolar macrophage will tackle pathogens that enter the small alveolar sacs in your lungs. In contrast, microglia control immunity in the brain and clear away old and dead neurons.

Overall, you’ll find that macrophages are on the front line of infections when your body encounters them. They respond to calls for help from various tissues when they’re suffering due to an infection.

How do macrophages work exactly?

Although the science world knows a lot about the macrophage role in immune response, it doesn’t understand everything. What is clear, however, is that macrophages reach their target when they receive a call for help. This call for help usually comes in the form of chemical signaling. When the macrophages receive those signals, they travel to the area they came from and begin their work.

One example of this is if you fall over and graze your knee. After 24 to 48 hours, you may notice some redness and swelling. This is because the knee injury sent signals out requesting help, so the macrophages arrived to eat any pathogens in the area, and they helped to release fluids that seal the area off a little to protect it. This is known as phagocytosis followed by inflammation.

Macrophages’ role in immune system adaptation and activation

Aside from their initial response to a pathogen, macrophages can set your immune system up so that it responds better to viruses. After they’re done eating a pathogen, they produce something called an antigen. They then take this antigen to a relevant helper T cell, work it into the cell membrane, and create something called an MHC Class II molecule. Eventually, this results in the production of antibodies against the virus that started the process.

If the same infection makes itself known again, the macrophage’s work has made it easier for the body to fight it. The body will know what a processed version of the infection’s antigen looks like, so the immune system remains on high alert for unprocessed versions. When unprocessed versions arise, they are recognized quickly, and the immune system tackles it more effectively. As a result, you’re less likely to develop the same symptoms that come with an initial infection.

Cytokines produced by macrophages

When a macrophage is exposed to an infective substance, it produces something called a cytokine. Most of these cytokines are referred to as tumor necrosis factors, and there are lots of variations. Cytokines help macrophages, T cells, and B cells interact with inflammatory and hematopoiesis cells. It’s useful to think of each cytokine as a messaging signal that will only work on certain receptors. When it reaches its desired signal, it’ll produce an effect that assists with your immune response.

For example, if a cytokine targets the chemokine family, it encourages cell migration that helps with healing. Or, if it reaches the interferon family, it will create an antiviral protein that allows your body to form an adaptive immune response.

The macrophage role in immunity can often feel complex. But, it’s also fascinating and worth learning more about.