Naive lymphocytes are immune cells that are mature, but have not yet been exposed to an antigen. These cells move freely through the immune system and play an important role in the development and maintenance of immunity. At any given time, the body continuously produces new cells. This can keep the supply steady and reduce the risk of gaps in immunity caused by depletion of immune cells as they respond to infections. Researchers with an interest in immunity and related subjects may work with naive lymphocytes in some settings.
B cells, produced in the bone marrow, and T cells, matured in the thymus, can both circulate through the body in a naive state. When these cells encounter an unfamiliar epitope, a specific protein on the surface of an antigen, they can formulate a reaction to it. This allows the immune system to continuously learn to recognize new infectious agents and mount responses to them. Once naive lymphocytes have been exposed, they activate, and begin mediating immune responses.
The maturation of lymphocytes in the body requires a series of steps which the body uses to develop functional cells and eliminate those that might react to antigens produced by the body itself. In patients with immune dysfunction, the numbers of circulating cells can drop, which poses a double risk. Patients may be less able to fight off known infections because the immune system doesn’t have enough strength to activate effectively. Their bodies also may not recognize new sources of infection with naive lymphocytes, which makes them vulnerable to new forms of diseases or exotic infections they haven’t encountered before.
Once T cells activate, they can produce more T cells, including specimens that will seek out and destroy cells carrying the recognized antigen. Others can act as helpers to mediate immune responses and clear the infection. B cells can present antigens after activation to assist the immune system, and also produce antibodies to resist organisms that might cause illness. These and other components of the immune system cooperate to provide protection from infection on a continuous basis, eliminating recognized antigens to prevent and fight disease.
Immune disorders can also interfere with the activation process for naive lymphocytes, causing problems with the way the immune system processes antigens. Some infections, like the Human Immunodeficiency Virus (HIV), actually hijack the immune system in the course of infection. This can make them challenging to fight, as it can be difficult to disentangle the virus from the patient’s own immune system.