Vaccination - Biology

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A vaccination is the injection of a killed microbe into the body in order to stimulate the immune system against the microbe, thereby preventing the disease. Vaccines are manufactured from the dead or attenuated bacteria, inactivated viruses, purified polysaccharides from bacterial walls, toxoids, and even recombinant DNA produced through genetic engineering. This is to immunize against viral diseases.

A healthy immune system is able to recognize the invading bacteria or virus and so produces antibodies to destroy or disable them. Only a small portion of the dead bacteria is generally required to stimulate the formation of antibodies against the whole bacteria. When an infection occurs the lymphocyte population responds. Both T-lymphocytes and B lymphocytes are formed by divisions of the stem cells in the bone marrow. The T-lymphocytes leave the bone marrow during development and differentiate in the thymus gland before circulating and storage in the lymph glands. T-lymphocytes carry out cell-mediated immunity, an immune response that doesn’t directly involve antibodies but does have a part in the activation of the B-lymphocytes. Certain T-lymphocytes are effective against pathogens within host cells.

While the T-lymphocytes leave the bone marrow before completing maturation, the B-lymphocytes complete maturation before leave the bone marrow to circulate around the body and be stored in the lymph nodes. If an antigen is found, humoral immunity takes place. This is when B-lymphocytes proliferate into plasma cells that secrete antibodies into the blood stream.

Both T-lymphocytes and B-lymphocytes have molecules on the outer surface of their plasma membrane, enabling them to recognize antigens. However, each lymphocyte has only one type of surface receptor and therefore can only recognize one type of antigen.

As mentioned before, the lymphocyte population responds when an infection occurs by an increase in number and collection at the...
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