Vaccines & Your Immune System
Your immune system is unique in that it is able to learn and remember. Vaccines take advantage of this special ability, allowing for the development of immunity to a harmful organism without actually being infected by it. However, vaccines are accompanied by possible side effects.
The Adaptive Immune Response
There are two kinds of immune response: innate and adaptive. Vaccines invoke the action of the adaptive immune response and as such will be the focus of this article. An adaptive immune response takes place when the body encounters something it has never seen before. Antigen-presenting cells engulf the foreign object, digest it into smaller pieces called antigens, and then present those antigens to T cells in the lymph nodes. T cells who recognize any of the antigens instruct other cells called B cells to create antibodies against the antigen. Antibodies are particles which bind to foreign objects, drawing attention to them and aiding in their phagocytosis (engulfment by cells) and subsequent destruction.
When a B cell is activated by a T cell it first proliferates, making multiple identical copies of itself. This creates a large population of identical B cells, greatly increasing the amount of specific antibody that can be produced. While proliferation is occurring, a small portion of B cells become memory B cells. Most proliferated B cells will die off eventually, but memory B cells are extremely long-lived, some remaining as long as the body is alive. When the body encounters something it has already seen before, memory B cells quickly recognize the invader and mount a response. Often this response is so quick that an infection doesn't have time to develop and therefore few or no symptoms are felt.
How Vaccines Work
Vaccines contain antigens or disabled microorganisms which stimulate the adaptive immune response. Antigen-presenting cells take up the injected antigen just as they would a microorganism, bringing it to T cells which then activate B cells. The creation of memory B cells during this response is vital to the success of the vaccine. Their synthesis allows the immune system to quickly fight off the actual microorganisms that the antigens originally came from, if ever encountered.
Types of Vaccines
There are three basic types of vaccines which are commonly used today.
- Killed Vaccines: usually contains viruses which have been rendered harmless with chemical destruction. Flu vaccines are composed of killed viruses.
- Attenuated Vaccines: these vaccines contain live microorganisms which have been altered in some way so that they are no longer harmful. The measles, mumps, and rubella (MMR) vaccine is an example of this type.
- Sub-Unit Vaccines: don't actually contain a whole microorganism but instead are created by purifying certain antigens from a microorganism, such as a surface antigen. HPV vaccines are created this way.
Many people have become reluctant to receive vaccines themselves or have their children vaccinated due to their side-effects and possible connections with diseases like autism. The chance of death from measles is 1 in 500 while the chance of death from the measles vaccine is 1 in 1 million. The debate about the necessity of vaccination will likely continue since there is no right or wrong answer. Those who wish to avoid excessive vaccinations can keep their immune systems strong with proper nutrition and other natural methods. Sources: