Merck Manual

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Basic Y Structure of Antibodies
Basic Y Structure of Antibodies

An antibody molecule is basically shaped like a Y. The molecule has two parts:

  • Variable part: This part varies from antibody to antibody, depending on which antigen the antibody targets. The antigen attaches to the variable part.

  • Constant part: This part can be one of five structures, which determines the antibody’s class— IgM, IgG, IgA, IgE, or IgD. This part is the same within each class.

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Acquired Immunity