The immune system is a complex network of organs, tissues, cells, etc… that protect us from outside attacks by infectious organisms and diseases.
As we move from adolescence into adulthood, our immune system gradually becomes strong. Our bodies create antibodies, which help us fight infectious diseases. Most people notice this when they stop getting sick as much; when we were children, colds and flus were much more common.
This increase in immunity does not last forever, after a certain point the immune system starts to regress and move in the other direction. This is why elderly are much more susceptible to getting sick (btw: supplements have been shown to not only not help with increasing immunity but to hurt the immune system and increase the risk of prostate cancer, etc..).
Here are some interesting stats that show us why this is the case:
The thymus, a specialized organ of the immune system, produces T Cell, which are a key component in cell-mediated immunity. The thymus is the largest during adolescence and as we age gets replaced by fatty tissue. By the time we are middle aged, the Thymus is at 15% of its original size and effectiveness.
Since T-Cells …