INNATE IMMUNE SYSTEM - CHEMICAL BARRIERS
We just looked briefly at chemical barriers when we were discussing physical barriers, but now we can look more closely at this aspect of our immune defence.
|
As we discussed in the previous section, the mucosal membranes secrete certain chemicals that help to prevent our bodies from being invaded by micro-organisms. |
However other parts of our bodies also secrete chemicals which help to defend us.
For example, tears contain lysozyme which is secreted from the lachrymal glands, and lysozyme is a bactericidal enzyme - therefore, it is good to cry ('bactericidal' means 'toxic to bacteria').
In addition, saliva also contains these bactericidal enzymes.
It is a good idea to try and remember lysozyme, because it occurs when we discuss various other parts of the immune system.
|
The pH of the body is important, because bacteria cannot exist in an acidic environment. |
The pH of the hydrochloric acid in the stomach is 3, and is therefore very acidic.
Hydrochloric acid in the gastric juices helps to sterilise and make safe any food that we eat.
As you know, all food, unless it has been sterilised by cooking and is eaten straight away, will contain some micro-organisms.
The vast majority of these micro-organisms will be harmless, for example some of the yeasts, but there may also be potentially harmful organisms, such as salmonella.
|
The female genital passages also have a pH value that can help to protect us from infecting micro-organisms. |
|
There are also anti-bacterial proteins and zinc (which helps immunity) in semen. |
|
We have all ready discussed the fact that skin is an excellent physical barrier, however it has a more varied role to play in our defence. |
As you know, there are sweat glands in the skin that secrete sweat, but what you may not know is that sweat contains bactericidal enzymes (remember that bactericidal just means toxic to bacteria).
Consequently, when you sweat, your immune system is working for you - therefore it is good to sweat.
Breast milk - and particularly colostrum - contains both protective bactericidal enzymes and certain antibodies (so breast milk can be seen to be part of the innate immune system and the acquired immune system - antibodies are a part of the acquired immune system).
| REFLECTION
You can think of all these elements of the innate immune system as being concerned with chemical warfare. Due to the stomach secretions being so acidic, most of the micro-organisms will be destroyed. Many of the secretions of the body, including saliva and tears, contain the enzyme LYSOZYME, which promotes cellular breakdown in bacterial cell walls, and so causes the death of bacteria. |