The human immune system is designed to protect our body from invading pathogens and other external dangers. But this is not the only function. In fact, our immune system is increasingly being recognized as being the central processing unit of good health. The functions of the immune system encompass multiple additional critical roles in regulating tolerance, immune surveillance, tissue repair, apoptosis, homeostasis, and overall biophysiological balance. Without the immune system, not only would we be unable to protect ourselves from pathogenic microorganisms, but we would not be able to learn to tolerate essential entities that help sustain our species such as food, fetuses, or commensal bacteria. Neither would we be able to combat neoplasms nor slow down the aging process. Our understanding of the immune system over the past 50 years has allowed us to artificially divide the immune system into two primary components, namely, innate and adaptive immunity. These concepts help us build a foundation on which to understand the billions of cells, molecules, and networks that comprise a functioning immune system and allow the student to better understand the overall workings of this system, instead of trying to rote memorize billions of unrelated facts.
