A recombinant antigen is a molecule made of multiple different types of proteins that triggers an immune response. Depending on the types of proteins contained inside the antigen, a particular antigen may stimulate production of multiple types of antibodies. This mechanism is often employed in medicine to purposefully encourage the human body to produce antibodies, such as vaccines. The antigens in vaccines provoke an immune response tailored to their recombinant structure.
Proper immune responses to a recombinant antigen are essential when stimulating long-term resistance to disease. Some antigens stimulate the immune system powerfully enough that one exposure confers a lifetime of protection against them in the future, while others produce a milder response that lessens over time. Certain vaccines need only be given once, since a single antigen exposure is enough to protect a person for life, while others must be given periodically over the course of an individual's lifetime so resistance does not drop below a critical level and leave him or her vulnerable to illness.
A recombinant antigen does not always come from an external source. The human body can produce its own antigens inside cells, both during normal and abnormal function. Cancer tumor cells produce antigens which stimulate a variety of responses in the human body besides antibody production, including inflammation. The production of antibodies does not guarantee that the body will mount a successful defense against an antigen, and while the situation may not always be as dire as cancer, antibiotics and other medications are sometimes necessary.
One of the more nefarious sources of recombinant antigens in the human body is drug-resistant bacteria. These bacteria are a significant problem because the human body either cannot develop proper antibodies against the antigens they carry or cannot generate enough antibodies. A recombinant antigen on a drug-resistant bacterium is created when multiple proteins on the bacterium's surface bind together in a way that makes certain antibiotics unable to destroy the bacterium. This resistance allows the organism to multiply and spread more recombinant antigens around its host. As more recombinant antigens are made, the chance of producing a resistant strain of bacteria grows.
Without recombinant antigens, effective medical treatments might be much harder to create. A lack of recombinant antigens may also make fighting bacteria much easier, because no microorganisms would ever become resistant to antibiotics. Recombinant antigens can promote both health and sickness, depending on the context, and the many contexts in which they appear make them simultaneously a tool and target in modern medicine.