Immunity is the ability of multicellular organisms to stop harmful beings from entering it. If you are immune to something then it means that it wont effect you. If you are immune to a disease then your body will prevent that disease from entering it and even if it somehow enters, your body will fight to keep you safe from the disease. Our body adapts to the disease which makes it difficult for it to harm us.
In a sense, immunity is the capability of the multicellular organisms to develop tolerance towards a particular disease as well as have the ability to fight the disease causing bacteria or virus when the situation arises.
Types of immunity
Active immunity refers to the phenomenon where our immune system itself prepares antigens to protect our body from unwanted pathogens. Active immunity occurs when our body is introduced to potential disease causing agents. Vaccines are a great method of introducing active immunity in the body to protect us from diseases in the future. The immune response of our body is greatly dependent on the vaccines which we have taken. Initially, vaccines provide a very slow and limited protection to the body from the pathogens. Gradually, increase in the doses of the vaccines help in the production of long-lived antibodies which further protect the body from disease causing organisms. The main goal of vaccines is to prepare the body so that in a future situation, if an individual is exposed to a certain disease, the immune system has enough antigens to help fight the disease preventing the harmful organisms from taking over the body.
Passive immunity is the process of introducing antibodies directly to the person in need of it. In such cases, the person is already suffering from a certain disease and their body might have not produced enough antigens to fight the disease. This provides immediate protection to the body but in the long run, it is important for the body to produce active immunity. Antibodies are also passed on from mothers to babies through breast feeding to protect the infants right after their birth. Antibodies can also be purified from the blood or in laboratories for short term protection. However, passive immunity only provides immediate protection and the body and the person will be at risk of being infected by the same pathogen sometime later.
The immune system is the defence system of the body which comprises of many biological structures and processes which protect the body from diseases. For an immune system to function properly, it must be able to distinguish between the harmful disease causing agents like various viruses and bacteria to the useful and beneficial organisms present in the body. The immune system roots out the germs and other harmful beings which have no business being in your body.
The immune system involves a lot of the components of our body such as tissues, cells, organs, proteins etc. it can distinguish between our tissue and foreign tissues which we do not need in our body. It can also find dead and faulty cells, which are of no use to us and can infect cause us harm, and clear them away without us even knowing.
Everyone has a different immune system but in general, our human system starts getting stronger by adulthood because by that time we have been exposed to a lot of harmful pathogens and have even developed immunity to a lot of them. This is why teenagers and children get sick more often than adults. Once an antibody has been produced in our body, it remains in there and stays there so that in the future if we are introduced to the same pathogen, our immune system can fight it easily.