|MadSci Network: Immunology|
There isn't a strict ratio of white blood cells to bacteria, the whole immune system acts in concert to destroy infectious pathogens, whether they are bacteria, viruses, parasites or fungi. The immune response can be divided into three general "branches", which interact and cooperate. Innate immunity is the part of the immune response that we all have, such as the skin that protects our inner organs. Humoral immunity is the antibody response to infectious diseases, and cellular immunity is (as it sounds) the cellular response. Cellular immunity is traditionally thought of as the cellular response to viruses. The antibodies that comprise the humoral immune response, however, are produced by a particular type of white blood cell, the "B" lymphocyte. B lymphocytes are activated and controlled by "T" lymphocytes, which are in turn activated by macrophages and dendritic cells. Macrophages and dendritic cells occupy a unique place in the immune response, serving as an integral part of all three branches: innate, cellular, and humoral. Macrophages literally "eat" bacteria, digesting them and presenting portions of them to T lymphocytes. At the same time, B lymphocytes pick up pieces of the bacteria as well and, in conjuction with signals from T lymphocytes, are then activated to produce antibodies against the bacteria. The antibody binds to the bacteria and, in turn, makes it easier for the macrophages to kill and digest the bacteria! So when you think of your immune response against a disease, whether it is caused by a virus or a bacteria, think of the response as a team working together to fight off the disease.
Try the links in the MadSci Library for more information on Immunology.