Wednesday, October 22, 2008

Give your immune system a chance..

I wrote this article for an annual newsletter for a small community of non-scientists. I thought it will be useful to post it on my blog as well. Here is the article.

Give your immune system a chance

If we don’t use a particular instrument for sometime, then it gathers junk. If we don’t use our brain often, then brain cells degenerate. Similarly, if we don’t use our immune system for sometime, then immune system starts corroding. What an amazing fact it is!! Yes, this is true… It is said that “If you take medicine, then cold goes away in just a week and if you don’t, then cold gets away in 7 long days”. The reason I chose to write this article is to introduce our amazing immune system in over simplified terms that we have little or no knowledge about.
Humans are highly evolved organisms belonging to class vertebrata that have a very well defined vertebral column. Almost all life forms have immune system. But this immune system has continuously improved to reach its highest state in jawed vertebrates. Humans are the highest life forms having the most sophisticated immune system. During evolution, immune system has been continuously undergoing modifications to help us fight elimination by natural selection.

Our Immune System:

Our immune system is broadly classified into two groups;
1. Innate immunity 2. Acquired immunity.
Innate Immunity is what we are born with and acquired immunity is what we acquire during our life time against certain types of response. The response could be infection, toxins, our own cells gone bad etc. Innate immunity comes to play as an immediate response to a threat to our body from an external agent – be it bacteria, virus, toxins, proteins etc. When innate immunity realizes that its resources are not adequate enough to fight against the disease causing agent, it passes the responsibility to the more sophisticated acquired immunity. Acquired immunity uses all its inbuilt tricks to fight against the attacker until it wins. Once the battle is won by the acquired immune system, the cells remember that. So, in future if there is an attack from a similar organism then the immune system reacts immediately, effortlessly. That is why we acquire life long immunity against a particular type of disease we already had.
Typically our immune system comprises of fighter cells and fighter molecules. The fighter cells are often known as B cells(Produced by Bone marrow) or T cells(Produced by Thymus) and the fighter molecules or antibodies are produced by these fighter cells. The fighter T cells often roam around within our system through our vascular system (blood/lymph network ) and clean it up when they see any foreign particle floating around. They do this by phagocytosis(Phago -> to eat; cytosis -> cellular process [Fig 1] ). It is interesting how they recognize the foreign elements. They generally have an antenna type of molecule on the top of their cell membranes that act as a sensor. The B cells are the factories that produce the sensor molecules. Through out our life time, our immune system builds its memory to identify good and bad elements. This system is highly efficient in humans and it not only eliminates our attackers but also cleans our own dead cells, cancerous cells and any other cell that has gone wrong by a process called as apoptosis. Typically if there is a new attack on our body, generally the memory forming cells try to look at its existing database and determine if the response is already preserved in cellular memory. If it finds out that it is not listed, then it goes back to its expression system, where it creates new fighter molecules that will be a fitting reply to the attacker.
Genetics of Immunity:
The attackers to our system produce a molecule (usually a protein) called ‘antigen’ and our body’s antidote for that is ‘antibody’. Often antibody binds and incapacitates the antigen and makes it inactive[Fig – 2]. Antibodies are highly specific and can identify millions of different antigens – in other words we are capable of producing millions of specific antibodies. As per the famous one gene one enzyme hypothesis (Beadle and Tatum's 1941 Breakthrough), we should have several million of genes to produce several million of antibodies, but we have in total only 30,000 or so genes in our body, and our immune related genes are not even more than a thousand.In that case how we are capable of producing millions of proteins from just thousand genes?
Structurally antibodies are comprised of 4 polypeptide(=proteins) - 2 heavy chains and 2 light chains. Each of these 4 polypeptides have a variable region and a constant region[fig-3]. The constant region forms the structural unit of the antibody while the variable region forms the functional unit. The variable parts are the ones that make the antibody so specific. Often the variable parts are the products of alternative splicing. So, now what is this ‘alternative splicing’? In order to understand the splicing event, we need to know little bit about the structure of our genes. Our genes have coding(useful) and non-coding(not so useful) regions. The coding parts are called as exons and the non-coding parts are called as introns. In a typical human gene, the exons and introns alternate with each other. Before a gene is expressed all the exons are joined together, that is translated to form a valid protein. In alternative splicing event all the exons don’t join together in the same order or same number. They join in different permutations and combinations. For instance if a gene has 4 exons, then it may join them to form > 4 products[Fig – 4].Here, we can’t speak strictly in mathematical terms because there are a certain sets of rules in splicing, that makes the straight forward calculation very complicated. This procedure of creating a specific product against a antigen can be compared to finding a drug target for a particular disease – only it takes place at a cellular level and it happens very quickly! The moment it finds the molecule that can fight against the attacker, it remembers that and starts producing them at a very higher number. The war takes place and generates heat. That is why often we develop fever against a certain infection. Once the fight is over, the product is remembered in our cellular memory. So, when there is another attack by same organism, we already have immunity against it. This is the same principle how the vaccination works. Vaccines are often the dead bacteria or viruses that cause a disease. Once injected into the body it elicits the immune response and it stays there for the entire life time. So, the individual gets immunity against that disease for the whole life.
Sometimes, the immune system can’t fight that well especially when our immune system is week or under utilized, it generally looses the disease fighting abilities. So, it is essential in that case to have medical intervention. In order to remain healthy we need to exercise our immune system as well and strengthen it.
Immune boosters:
Healthy habits are great immune boosters. The best food for healthy immune system is colorful fruits and vegetables. Apart from food, regular exercise, adequate sleep, drinking enough clean water, vitamins(mostly from natural plant sources – they get absorbed well), reducing stress helps improve our compromised immune system. So, the bottom line here is to increase our cellular memory so that it is capable of identifying a myriad of infectious particles and fight against it without much trouble.
Certain food are know to weaken our immune system are coffee, sugar, soda, alcohol, preserved food(mostly canned food). So to conclude: stay healthy, eat healthy and do regular exercise to minimize doctor visits.

Fig – 1: Phagocytosis

Fig – 2 : Antigen – Antibody binding

Fig – 3 : Structure of a immunoglobulin

Fig – 4 : Gene Structure and alternative splicing

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