acquired immunity

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Immunity obtained either from the development of antibodies in response to exposure to an antigen, as from vaccination or an attack of an infectious disease, or from the transmission of antibodies, as from mother to fetus through the placenta or the injection of antiserum.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun immunity to a particular disease that is not innate but has been acquired during life; immunity can be acquired by the development of antibodies after an attack of an infectious disease or by a pregnant mother passing antibodies through the placenta to a fetus or by vaccination