The term immunity means the defence of our body system against the dangerous substance or particles. Immunity can be against any sort of infection. When unknown dangerous particles enter the body, the body counter acts in order to prevent any sort of harm or danger. There are two major types of immunity. One is innate immunity and the other is adaptive immunity. Innate is however is inherited by the person from his parent. While the adaptive immunity plays a major role as a person grows time to time. The adaptive immunity has two further classes, the active immunity and the passive immunity. It could be both natural and artificial. The basic difference between the active immunity and passive immunity is that active immunity is against direct antigen or bacteria while passive immunity does not need any direct contact with the antigen or bacteria.
In active portion of innate immunity, the body produces antibody countering the antigen or bacteria. These antibodies are produced within the body apart from this they also form memory cells which are responsible to remember the antigen and to produce same antibodies when again the antigen attacks. For example an A antigen attacks the body, in reaction of this the body will produce MHC cell class 2 or MHC cell 1 in turn activating helper T cells which then activates B-cells (plasma cells) which are responsible to produce antibodies and memory cells. This is how our body generates their own antibodies against the antigen but this is a really slow process. The example can be exposure to pathogens and vaccination live attenuated and etc.
On the other hand of discussion in passive part of immunity, the preformed antibodies are directly injected in the body. These preformed antibodies are extracted from a particular donor. These preformed antibodies are injected directly into the veins of the victim of antigens or bacteria. The process of passive immunity is fast as compare to active immunity. The Fc potion of antibody IgG attaches to the antigen (virus) and eliminates it by killing it. No need of memory B-cells in it to remember the antigen. IvIG, that is, intravenous immunoglobulin that are given in certain diseases as a prophylaxis. It is mostly used in immune compromised patients as their bodies are unable to produce their own anti bodies for the purpose of immunity.
- Active immunity is necessary when pathogen comes in direct contact with the body while on the other hand in passive immunity no direct contact is required.
- The process of active immunity needs greater time as immunity needs to be developed through a certain process while on the other hand in passive immunity no such process is required as immunoglobulin are directly injected.
- In active immunity the antibodies are not developed instantaneously while on the other hand in passive immunity the antibodies are developed instantaneously.
- The active immunity lasts for longer time period even till death while on the other hand passive immunity last for few weeks or months.