How the Immune System Works

The primary function of the immune system, to say it in the most elemental (and oversimplified, but not altogether untrue) terms, is to distinguish between what is self and what is non-self, and then to eliminate the non-self. Thus, whenever a non-self substance breaks the normal skin and membrane barriers of the body and gets “inside the walls,” the immune system shifts into gear to meet the challenge. If the invader is a microbe, such as a bacterium or virus, macrophage cells seek it out, surround it, and try to ingest and absorb it. They then transport portions of it over to another cell in the system, the T4 cell, the cell that oversees and regulates the entire cellular and humoral immune response, and present the surface of that invader to the surface of the T4 cell for recognition. “See what I have here?” it seems to say. “Well, there are more out there just like this one, and they have the same coat this one has. Let’s gear up for them, train our troops to recognize them, and fight them off. What say? Should we get to battle stations?”1