How do we fight an infection?
Infection is simply the intrusion of disease-causing organisms like bacteria or viruses into our body, in response to which our body reacts and fights. Like there are guards at the entrance of a place to protect and restrict the access to unknown individuals, similarly our body has immune system to restrict entry of foreign substances or disease-causing organisms into our body and if they enter, our immune system fights for the maintenance of our health.
Our Immune system is a dynamic network of various cells and molecules that protects our body from various intruders. The system keeps on fighting with the harmful substances or organisms (pathogens) specifically microbes like bacteria, virus etc which we cannot see from our naked eye, to maintain our healthy state. As soon as the system becomes weak, it can’t fight anymore and we get ill! That’s why we need to have a strong immune system and nowadays especially in the ongoing COVID-19 pandemic, you must have heard a lot about immunity and boosting immune system. In fact there are lot many products or supplements are available in the market for the same, ranging from natural Ayurveda products to the chemically synthesized products.
So, let us have a brief look at our warrior- the immune system!
Innate immune system: the first line of defense
Innate immune system is very quick and responds within hours of infection. As a part of this system, the primary restriction to pathogen is provided by our skin (like a wall to a house), that’s why it is known as primary barrier. And now you can think of a wound or cut in your skin that is more susceptible to infection or to the entry of invaders in our body. Besides, there are other barriers as a part of innate system like mucous that entraps the foreign substances (think of increased mucous secretion during cold and flu that you frequently expel off); normal body temperature that inhibits growth of some pathogens (fever or high temperature is also a sign of our body fighting and inhibiting the growth of some pathogens); low pH of stomach that creates acidic environment and kills ingested microbes.
Secondary action is taken by the immune cells which have got specific receptors called as pattern recognition receptors that interacts with the specific structures of these invading microbes and provides a warning to activate defense program for elimination of these microbes. As a result of this interaction, inflammatory mediators are released causing inflammation, often seen as red, swollen or painful infected area. This keeps the infection localized and prevents from spreading and in the mean time immune cells comes for the rescue and eliminates the pathogens. Oh yes again our system won the fight! So, from next time you encounter any of such reactions, remember your innate immune system is at work and at that time particularly take good care of your health by having proper diet and rest so as to recover well.
Besides these barriers, there are some other key players of innate system i.e., immune cells as I mentioned previously which comes for the rescue. The granulocytes like neutrophils, eosinophils, basophils, mast cells; phagocytic cells like macrophages and dendritic cells; and white blood cells (you must have seen the count of these cells listed in blood report and usually during infection, their cell count is altered from the normal range). So, these cells are the frontline warriors we can say, that arrives quickly after receiving the warning given by barriers at the site of infection (and therefore increase in their cell count is a sign of infection) and helps in reducing inflammation, killing and elimination of the pathogens.
So, now you can think of how much important our innate immune system is! Recently a review article also highlighted the role of innate immune system as a defense against the ongoing infection due to SARS-CoV-2 virus, which can be possibly used for development of therapeutics for treatment and prevention of the disease.
Another partner: adaptive immune system
Indeed, innate immune system is very efficient and provides the primary line of defense. But what if it encounters an aggressive pathogen to which it loses! Don’t worry, it has got a partner- the adaptive immune system! As such there is no fixed time when adaptive system takes over and innate response stops, it’s always a communication between the two. But, unlike innate system, adaptive takes more time to respond (days after infection), and notably adaptive system has got memory that elevates the response against previously seen pathogens.
The key players of adaptive immune system are lymphocytes- B and T-cells. So, this system responds in two ways- 1. upon activation, B-cells produce antibodies against pathogens which helps in their neutralization and 2. T-cells activates other immune cells and also mediates killing and elimination of pathogens.
As the name says adaptive, it is constantly learning and adapting to fight against various pathogens as and when encountered.
The other characteristic features of immune system
· Immunity is systemic i.e., these immune cells can easily circulate among throughout the body and this forms the basis for vaccination also.
· Discrimination between self and non-self so that immune cells can differentiate between our own body’s cells/tissues and the invaders. If this discrimination is altered, it leads to autoimmune disorders like Rheumatoid Arthritis
· Besides the aforementioned immune cells, there are several organs (like bone marrow, thymus, lymph nodes, spleen and various lymphoid tissues) which are part of the immune system, that provides site for development and maturation of these immune cells.
Take good care of your immune system!
So, looking at the role of our warrior, our immune system, it is up to us how we support this system to win the fight against invaders. Taking proper diet, drinking plentiful water, doing regular exercise, managing the day-to-day stress, taking good sleep, keeping a check of nutrients and taking supplements if required, are the few measures that can help in optimizing our immune system and hence maintaining the healthy state of well-being!
