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Acquired Immunity

By Peter J. Delves, PhD

Acquired (adaptive or specific) immunity is not present at birth. It is learned. As a person’s immune system encounters foreign substances (antigens), the components of acquired immunity learn the best way to attack each antigen and begin to develop a memory for that antigen. Acquired immunity is also called specific immunity because it tailors its attack to a specific antigen previously encountered. Its hallmarks are its ability to learn, adapt, and remember.

Acquired immunity takes time to develop after first exposure to a new antigen. However afterward, the antigen is remembered, and subsequent responses to that antigen are quicker and more effective than those that occurred after the first exposure.

The white blood cells responsible for acquired immunity are

  • Lymphocytes (T cells and B cells)

Typically, an acquired immune response begins when antibodies, produced by B cells (B lymphocytes), encounter an antigen.

Other participants in acquired immunity are

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