An antigen is best defined as
Correct answer: D. any molecule the body recognises as foreign and responds to by making antibodies
- A. any protein made by a white blood cell
- B. a chemical that destroys bacteria directly
- C. a cell that engulfs foreign particles
- D. any molecule the body recognises as foreign and responds to by making antibodies
Explanation
Antigens are usually proteins or polysaccharides on the surface of a pathogen, a pollen grain or a transplanted cell, and their shape is what a particular antibody or lymphocyte receptor fits. The antigen provokes the response and the antibody is the body's answer to it, so confusing the two reverses the whole logic of immunity. Self molecules are normally not treated as antigens because self reactive lymphocytes are eliminated during development.
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About Specific Defense Mechanism
Specific defense mechanisms provide targeted immunity through B lymphocytes, T lymphocytes, antibodies and memory cells that recognize particular antigens. Questions cover humoral and cell mediated responses, clonal selection, primary and secondary immune responses, vaccination and passive immunity, while distinguishing adaptive defenses from the immediate, non specific innate response.
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