Some of the body's defenses include mechanical barriers such as skin, membranes and mucus, chemical barriers (such as tears and the juices in the stomach), and bacterial barriers (which are the presence of productive bacteria that counter-balance the harmful ones). Another defense is the production of both white blood cells that surround and attack harmful bacteria and antibodies that kill or weaken the invaders. The body has thousands of different antibodies, each capable of weakening or destroying a certain disease. Toxins from the microorganisms can be neutralized by certain antibodies, and if the body doesn’t produce enough of these antitoxins, a physician may inject more antitoxins. T-cells in the body protect against viruses that grow inside human cells. The body “remembers” these battles because the antibodies remain in the body for long periods of time, which produces immunity to the disease. The body also may become feverish, which increases the rate of the immune system’s reactions, speeds up white blood cells, and may kill or weaken the dangerous invaders. 

Bacterial Infections

A bacterial infection can be treated with antibiotics which will kill the bacteria. One of these antibiotics is penicillin. Penicillin prevents bacteria (bacteria are like a bag of fluid protected by a rigid network of girders built out of carbohydrate molecules), at cell division from forming chemical bonds needed to build their external skeleton. Antibiotics have been effective against bacterial infections, but some bacteria are now becoming resistant to antibiotics.

Viral Infections

In order to get rid of a virus, the cell which has been invaded by the virus must be killed, which results in damage to the cells themselves. For this reason doctors can only control the symptoms of a viral infection, but have not found cures. When viruses invade the body, the immune system releases white blood cells. These cells produce antibodies which cover the virus’s protein coat and prevent it from attaching itself to the cell. White blood cells also destroy infected cells and thus kill the viruses before they can reproduce. Unfortunately, some viruses such as measles, influenza, and AIDS suppress the immune system.