The adaptive immune system can be broken down into two components: cellular and antibody-mediated immunity. The hallmark of both these defenses is their inherent versatility to adapt immune responses to target specific infectious causes. Of note also, is that these adaptive defenses remain in place for extended periods, giving rise to "memory" against infectious agents - this mechanism is utilized in the process of vaccination.
Over the past few years, our understanding of how the immune process functions has given rise to novel treatments which "direct" or "train" our immune system to attack specific markers within our body. Though this is true for both components of the adaptive immune system, synthetic antibodies have been in the market for some time and are becoming increasingly popular.
Antibodies can be thought of as having a head and a tail region. The head structure captures the intended target while the tail region encourages destruction of what the head is attached to. The synthetic antibodies produced in the lab are designed to be just like natural antibodies. While antibodies can be given as a supplement for those who lack the capacity to produce natural antibodies, they have much wider applications. Take for example Infliximab (drugs that end in -mab are generally antibodies), it targets TNF-alpha which is a mediator of inflammation, and thereby inhibits its action. TNF-alpha is produced in the body during times of infection. However, its over function can lead to excessive inflammation. This is seen, for instance, in patients who have severe cases of autoimmune disease. There are many other examples of antibodies designed to attack specific targets in our body, particularly in the fight against cancer.
This unique ability to target specific threats is making synthetic antibodies an interesting new tool for fighting disease and hopefully it will continue to demonstrate successes.