Chapter 1: The Human Immune System

Abstract

We live in a world full of microorganisms as there are microbes in almost every habitat in nature. From easy-to-live places such as soil, food, and surfaces that are commonly used, to more extreme places such as hostile thermal vents at the bottom of the ocean, scorching hot and extremely dry deserts, and frozen snowfields, microorganisms are able to inhabit and colonize almost everywhere on earth. This means that they are also found inside virtually every living organism, including humans. Foreign microorganisms and viruses that are able to enter the human body and cause infection or disease are called pathogens and although the debate to label viruses as microorganisms still continues, this chapter will consider them as so for simplicity. Because pathogens can cause harm to us, our bodies have a natural defense, the immune system, that not only eliminates the pathogen but also prepares the body for a potential future infection of the same pathogen. This chapter will focus on what the immune system is,differentiate  types of immunity, and detail the specialized functions of the immune cells that make it up.