A Cold Explanation
Come December most of Britain are woefully carrying round a pack of tissues and feeling rather sorry for their noses. However, as common as the cold is, many of us are oblivious to the events occurring internally.
To start with, all colds are caused by viruses. This is why antibiotics, which are only effective against bacteria, are useless against a cold. Viruses are tiny non-living infectious agents that consist of genetic codes wearing a protein coat and sometimes an additional outer shell of lipids for disguise. Because they are not themselves living, they can only reproduce using a living organism’s replication machinery.
The virus travels through the air, propelled by a poorly persons’ sneeze. A single particle is sufficient to cause an infection. It reaches another nose and is carried into the depths within to begin its nasal cell invasion. Each virus particle occupying a nasal cell will spark an inflammatory reaction; this is what causes the typical swelling and runny nose symptoms. The virus then hijacks the cell’s replication machinery to produce multiple copies of its self. The newly formed gang of viruses then burst out of the host cell to voyage around the body, repeating the process of infection.
Luckily for us, some of these viral particles end up in the lymphatic system; a circulating fluid full of antibody-expressing B cells. Each virus expresses a very specific antigen, only detectable by one unique B cell receptor. When the virus finds a compatible B cell, it binds to the receptor with the intention of invasion, but is immediately engulfed into a trap- the lysosome. Enzymes in the lysosome digest the virus into fragments, which are subsequently expressed on the outside of the B cell as a warning signal to other white blood cells. These other cells then recognise the foreign particle and instruct the B cell to produce as many antibodies as possible, and to multiply fast. The released antibodies instigate execution of all viral particles. Some B cells stay as memory cells just in case the same virus is encountered again. Sadly however, with 200 possible cold-causing viruses and rapid mutation rates, the same one is rarely encountered twice.
Although it may be somewhat true that immune defenses are weakened when the body is cold, it is a common misconception that you can ‘catch’ a cold simply from being cold. Some scientists suggest that cold causing viruses may be more active in winter, or it could be that more time spent indoors in close proximity to one another means faster transmission. Nevertheless, a combination of nutritious food, good hygiene and lots of rest is still the best defense known!