1) Resistance to infection because of previous exposure to an infectious agent, naturally or by vaccination 2) State of activation of the immune system to recognize a foreign substance
The body's means of protection against microorganisms and other foreign substances; it is composed of two major parts: the humoral response (B lymphocytes and production of antibodies) and the cell-mediated response (T lymphocytes that attack foreign substances directly).
one of a group of proteins released by cells of the immune system that carry signals to neighboring cells to regulate and/or promote an immune response
Organ located behind the upper breastbone at the base of the neck that is part of the lymphatic and immune systems; disease-fighting white blood cells called T-cells develop and mature in the thymus before entering circulation. In humans, the thymus is normally active in childhood but becomes less active after puberty, eventually losing most immune...
Misdirected immunity with production of antibodies that act against the tissues of one's own body