Immunology inside body cavities

When you think about an immune cell, where do you think it lives? In the blood? In the bone marrow? Lymph node? Spleen? 

 

Those are all correct, in fact, a drop of blood may contain 7,000 to 25,000 immune cells, and the bone marrow is a place where immune cells are made. The lymph node and spleen are also important organs that generate and facilitate immune responses.

 

Immune cells are everywhere in your body, ready to fight an infection or repair an injury. You will find many different immune cells in all of your organs, including your brain, bones, eyes, and muscle. Think about it. You need a defense system at the ready just in case a pathogen finds its way into that organ. 

 

When you think about an immune cell, you may not think about your body cavities as a place where immune cells live.

 

Body cavities such as the peritoneal cavity (in your abdomen), the pleural cavity (around your lungs) or the pericardial cavity (around your heart) not only provide structural support for their surrounding organs, but also have important immune functions as well.

 

If you remember from my previous ImmuNews post, tissue-resident macrophages will have a specialized function depending on its location. It turns out that inside these body cavities are resident macrophages (called GATA6+ macrophages, or cavity macrophages) that do some pretty amazing things. 

 

For example, my lab recently discovered that cavity macrophages can migrate from inside the peritoneal cavity toward an injured liver, and their job is to help repair the wound. Some authors described this migration as a "wormhole travel" for macrophages.

 

Without cavity macrophages, the liver was unable to heal, and this highlights the important job for these immune cells within body cavities. 

 

Like I said in my previous post, there are still many unanswered questions in science. This new finding for cavity macrophages opened up a fantastic new area of immunology that is really exciting. Here are just a few questions you can think about:

  • Are there different immune cells other than macrophages inside body cavities that play important roles in injury or infection?
  • Are there similar cells surrounding other body cavities such as the lung (pleural cavity) or the heart (pericardial cavity) that might protect those organs? 
  • Do cavity macrophages play a role in other diseases such as cancer? Would they be beneficial or detrimental towards the cancer?

 

Thank you for reading! Hopefully you will now know a little bit more about what goes on in the space between your organs. It's not just water, there's a lot going on!

 

-RMK

 

Reference: 

Wang, J and Kubes, P. A Reservoir of Mature Cavity Macrophages that Can Rapidly Invade Visceral Organs to Affect Tissue Repair. 2016. Cell, Volume 165, Issue 3, 668 - 678.