A state of nonresponsiveness to a particular antigen or group of antigens. Agents produced by plants and bacteria, normally very damaging to mammalian cells, that can be delivered directly to target cells by linking them to monoclonal antibodies or lymphokines. A substance that contains antigenic components from an infectious organism. That part of an antibody's structure that differs from one antibody to another. Submicroscopic microbe that causes infectious disease.
Viruses can reproduce only in living cells.