Effectors are agents or structures that cause an activity, like a nerve causing a muscle to flex, or a cell triggering an immune response to a foreign substance. An effector can also be a molecule that binds with a protein and alters it, by either causing an increase or decrease in its activity. Effector cells are found in the nervous system as well as the immune system. Nerve endings act as effectors when they carry impulses to different glands, muscles, and organs to cause flexing, secretions, and other functions.
Molecules that are effectors can act as activators or inhibitors. As an activator they can bind with an enzyme and cause it to increase its activity, and an inhibitor does the opposite. This type of effector is widely used by the pharmaceutical industry.
Certain drugs act as inhibitors in order to fix a chemical imbalance or kill a pathogen. Pathogens are microorganisms that can potentially be harmful to the body. Protease inhibitors are used to treat viruses. A protease is an enzyme that breaks down proteins. The inhibitor interferes with how the virus functions and inhibits its activity.
In terms of the immune system, effector cells, or B and T lymphocytes, are produced in response to a particular stimulus, like an antigen, to perform a particular function. Lymphocytes are short lived cells that are part of the body’s immediate immunological response. Effector cells are one type of cell produced during clonal selection. Clonal selection is the process in which B and T lymphocytes are created, and is a part of the primary immune response.
The entire immunological repertoire of a human being is developed in the womb because each lymphocyte has a unique antibody on its surface. When an antigen — which can be any foreign substance — enters the body, it is met with lymphocytes. Each lymphocyte can distinguish between various antigens using proteins on its surface called antigen receptors. Once a proper match is made, the proper antibodies can be produced.
Another type of immunological effector cells are memory cells. Memory cells are not actively involved in the primary immune response, but are very important for the secondary immune response. These cells are produced during the primary response, and this is how a body remembers how to counteract antigens that it has encountered before. If an antigen enters the body a second time it will trigger a secondary response by the memory cells. Every time a body is exposed to a particular antigen, the number of memory cells increases.