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germ theory

theory that states that diseases are caused by microscopic particles called pathogens


agent that causes disease


organism, such as a mosquito or tick, that transfers pathogens from one host to another

immune system

body system that fights off infections


cell that destroys other cells by surrounding and engulfing them

T cell

white blood cell that matures in the thymus and destroying infected body cells by causing them to burst; also called a T-lymphocyte

B cell

white blood cell that matures in the bone marrow and produce antibodies that fight off infection; also called B-lymphocyte


protein produced by B cells that aids in the destructio of pathogens


type of protein, produced by body cells, that prevents viruses from replicating in infected cells

passive immunity

immunity that occurs without the body undergoing an immune response

active immunity

immunity that occurs after the body responds to an anitgen


immune response that is characterized by swelling, redness, pain, and itching


protein marker that helps the immune system identify foreign particles

memory cell


cellular immunity


humoral immunity


tissue rejection



chemical, such as soap, vinegar, or rubbing alcohol, that destroys pathogens outside the body

anitbiotic resistance

process by which bacteria mutate so that they are no longer affected by an antibiotic




immune response that occurs when the body responds to a nondisease-causing antigen, such as pollen or animal dander


antigen that does not cause disease but still produces an immune response


severe allegic reaction that causes airways to tighten and blood vessels to leak



oppurtunistic infection


human immunodeficiency virus (HIV)


acquired immune deficiency syndrome (AIDS)

condition characterized by having several infections and very few T-cells; caused by HIV

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