- any of the body’s immunologic reactions to an antigen.
- the reaction of an organism’s body to foreign materials (antigens), including the production of antibodies
- An integrated bodily response to an antigen, especially one mediated by lymphocytes and involving recognition of antigens by specific antibodies or previously sensitized lymphocytes.
- A protective response of the body’s immune system to an antigen, especially a microorganism or virus that causes disease. The immune response involves the action of lymphocytes that deactivate antigens either by stimulating the production of antibodies (humoral immune response) or by a direct attack on foreign cells (cell-mediated immune response.) An inability to produce a normal immune response results in immunodeficiency diseases such as AIDS. See also cell-mediated immune response humoral immune response.