Mucus

An under-appreciated defence system

A mucus layer coats the body surfaces that are exposed to the external environment.

Why do we have mucus?

Because it traps the dirt and germs.
It holds on to all the good stuff our immune cells make to kill the germs.
Thats why we make lots of mucus when we are sick! To trap the germs and cough them all up.

What is in mucus?

Mucins are large sugar covered proteins in the mucus. These proteins attract water and give the mucus its gloopy gel like consistency.
Anti-microbials are secreted by different cells in body. These get trapped in the mucus and can help kill the germs.
Antibodies are secreted by immune cells known as B cells - these are an essential part of the protection at the mucus barrier.

Where does mucus come from?

**Goblet cells** are specialised cells in the body which secrete mucins. They are “goblet” shaped. Goblet cells
have granules which store the mucins and secrete these into the mucus layer giving it the “goop” like consistency.

*Hasnain SZ. Biological Science Review (2010). 23: 16-21*

What happens when mucus goes wrong?

Cystic Fibrosis is an inherited disorder. The mucus in the airways becomes thick and sticky and difficult to move, which hinders breathing. The thicker mucus in the lung also becomes a breeding ground for bacteria and makes patients more prone to infection.

In asthma, similarly to Cystic Fibrosis, results in a sticky thick mucus making it harder for patients to breathe.

Sjögren's Syndrome is an autoimmune disease. The immune system attacks healthy cells in the body that make mucins (mucus). This causes dryness of mouth, eyes and other membranes of the body that secrete mucus.