Pathogens are harmful bacteria/ viruses that disrupt the normal functioning of tissues or organs or an entire organism. However, if the rate of their reproduction is less than the rate at which they are killed, one does not feel the effects of it and they show no symptoms.
If the rate of reproduction is higher than the rate at which they are killed, symptoms arise and one would feel ill.
Pathogens are destroyed by white blood cells. There are two different types:
1. Phagocytes
2. Lymphocytes
Phagocytes kill pathogens by engulfing them. However, this does not necessarily occur at a high rate and most of the time, lymphocytes are involved.
There are two types of lymphocytes: T cells and B cells.
Sequence of specific immunity
Phagocytes encounter a pathogen and begin to engulf it. Whilst doing so, it displays the pathogen's antibodies which alerts a t cell.
The t cell in turn alerts a b cell with the specific antibodies needed to target this pathogen.
The b cell begins to divide and produce antibodies in huge quantities.
The antibodies neutralise the toxins produced and cause the pathogens to clump together so that the phagocyte may engulf them all at the same time.
Some of the b cells are stored in the lymph nodes incase this pathogen is encountered again.
This sequence of events is called the specific immune response as it is targeting specific pathogens through the use of antibodies.
Vaccinations
Vaccinations work by injecting a weak version of a pathogen into the body. The antibodies specific to these pathogens are then produced by b cells. These increase the rate of destruction of these pathogen then they are stored in the lymph nodes where they are kept until the same pathogen is encountered again and a faster response is required. Future antibody production would be quicker and in a larger quantity thus targeting the pathogen faster.
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