Immunity Definitions
Immunity: the body’s specific protective response to invading foreign agent or organism
Phagocytosis: monocytes responsible for engulfing and destroying foreign bodies and toxins
B lymphocytes: mature in the bone marrow
T lymphocytes: mature in the thymus, where they also differentiate into cells with various
functions.
Attack invaders directly, secrete cytokines, and stimulate immune system responses
Recognition stage: the body recognizes the antigen as foreign.
Lymphocytes recirculate from the blood to lymph nodes and from the lymph nodes back into the
bloodstream in a continuous circuit
Proliferation stage: Circulating lymphocytes containing the antigenic message return to the
nearest lymph node and stimulate some of the resident T and B lymphocytes to enlarge, divide,
and proliferate. T lymphocytes differentiate into cytotoxic (or killer) T cells. B lymphocytes
produce and release antibodies
Response Stage: Begins with the production of antibodies by the B lymphocytes in response to a
specific antigen. Cellular response stimulates the resident lymphocytes to become cells that
attack microbes; (killer) T cells
Effector stage: Humoral Immunity= Interplay of antibodies. Cellular Immunity=Action by
cytotoxic T cells.
Apoptosis: Programmed cell death
Allergy: An inappropriate, often harmful response of the immune system to normally harmless
substances
Hypersensitive reaction to an allergen initiated by immunologic mechanisms that is usually
mediated by IgE antibodies
Allergen: the substance that causes the allergic response
Atopy: refers to IgE-mediated diseases, such as allergic rhinitis, that have a genetic component
Allergic reaction: Manifestation of tissue injury resulting from interaction between an antigen
and an antibody