The immune system is comprised of three different systems that actively fight foreign material in the human body. It excludes such "first line" defences as the skin (a barrier against infection) and stomach acid (which kills bacteria in food).
Histamines are chemicals produced by the body in reaction to foreign bodies that have penetrated the skin, digestive tract or mucous membranes. They cause inflammation in the affected area which draws more of the body's defences to the area of the infection or other invasion. Typically, histamines cause swelling of the affected tissues. A typical histamine reaction is the swelling that results from an insect sting.
However, histamines are also responsible for secondary symptoms, such as a runny nose or coughing. A runaway histamine response to a non-threatening foreign body is known as an allergy. A severe allergic reaction can result in anaphylactic shock.
White Blood CellsEdit
White blood cells, or leukocytes, are produced in the bone marrow and are present in all healthy human beings. White blood cells can identify material that does not match the genetic makeup of the patient, surrounds them and kills them. The detritus then either is processed by the liver or collects somewhere in the body as pus. In response to an ongoing infection, the bone marrow produces more white blood cells.
One important diagnostic test is to do a white blood cell count, which determines if the body is able to fight off infection or is doing so. A low white cell count usually indicates a serious condition, such as leukemia or radiation sickness. A high white cell count can either indicate a serious infection or an autoimmune disease
Antibodies are produced by the lymph nodes, and are specific to the particular foreign body being fought off. They allow other cells in the body to target the invading foreign cells. However, it can take days or even weeks for new antibodies to be manufactured by the body. However, when they are, the foreign bodies are usually destroyed very quickly. Once a patient has had a particular disease, the process of producing antibodies is much quicker. As such, once a patient has had a disease, they rarely develop it again even when re-infected. This is the process that allows vaccination to work.
Main article: Immunosuppression
Several conditions can suppress the immune system. Most common are leukemia and radiation sickness. However, there are some genetic disorders that leave patients without an immune system. In addition, transplant patients have to have their immune system artificially suppressed with drugs to keep their immune system from destroying the transplanted organs.
There are several conditions where the body's immune system attacks healthy cells. The best known of these is Lupus.
Dr. Cameron is the team's immunologist, or specialist in diseases of the immune system. One of the ongoing themes in the show is that she almost always suggests Lupus as a diagnosis for the patient. Although Dr. Cameron is right that Lupus can manifest itself in a number of ways, Dr. House usually points out that by that logic every disease is Lupus.