It’s been years since I suffered from a “flu like illness”, years since I’ve had a cold at all in fact. But this week my luck has run out and I’m distracting myself by writing about the way the immune system reacts to viral infections.
As soon as a virus starts invading your respiratory membranes the innate division of your immune system detects the problem and swings into action. It produces chemicals known as cytokines that cause the symptoms we associate with a cold: mucus production, sneezing, stuffy nose and cough. Cytokines also affect your brain, making you feel lethargic. The body’s temperature control centre (also in the brain) may be affected, causing a “temperature”. Inflammation is another feature of the innate immune system, hence the sore throat and pink eyes. It’s not the virus itself that causes all these effects – it’s the innate immune system reacting to it. In some viral diseases, such as pandemic flu, the immune system reaction can be so severe as to cause death.
While all this is going on and you’re struggling to carry on working, or flopped around apathetically watching daytime TV, the adaptive branch of the immune system is also working hard in the background. A swollen gland or lymph node can accompany this activity. A production line is being set up for B lymphocytes that will release antibodies against this particular virus along with a flood of uniquely-targeted T lymphocytes that will destroy the virus-infected cells. The process of getting this second-wave attack off the ground takes 4 - 7 days.
Sometimes the innate system does the trick and you “shake off the cold” quite quickly. On other occasions you just have to wait until the adaptive system is in full swing and has cleared the virus from your system.
Ibuprofen and paracetamol are helpful for relieving many of the symptoms. They are not cures however - nothing is, apart from the immune system itself.
Doctors call these viral infections “self-limiting illnesses”. Sit them out and your immune system will make you better. The body in this case is its own healer, rolling out an incredibly sophisticated dual-phase 100% successful cold cure.
In a few cases there are complications caused by bacteria which like to breed in the soggy, congested corners of the respiratory system. Babies and toddlers are more susceptible and chest infections are the most worrying. The immune system changes throughout life and as people move into their 60s and beyond they too also more likely to get a chest infection.
A bacterial chest infection that needs antibiotics is something more than just a cough. For symptoms, when to worry and other vulnerable groups see:
The adaptive immune system remembers each virus it has encountered and will deal with it swiftly in future. However there are many viruses that can cause these annoying infections and because they keep mutating you will never, however long you live, be able to fend off every one.
The one I’m grappling with this week is rather persistent – but 5 days in now and I’m beginning to feel a slight lifting of the inertia that has consumed my week. I have, at least, finished writing this blog. But my patience is wearing thin, so do your stuff now, adaptive immune system, bring on those lymphocytes and bring me relief.