VMC 221: Veterinary Immunology and Serology (1+1)

TEMPLATE HYPOTHESIS (INSTRUCTIVE THEORY)

• Breint and Haurowitz proposed this theory in 1930.There are two types of template hypothesis
• Direct template hypothesis
  • According to this theory, antigen must enter the antibody forming cells and there are configuration changes in the antibody producing cells.
  • The antigen acts as a template (mould) for which complementary structure of antibodies are made by the cells.
  • Antibody is synthesized in direct contact with the antigen and then dissociate leaving the antigen free to act as template for further synthesis. Thus mirror image of antigen is formed with its specificity.
• Indirect template theory
  • Burnet and Fenner (1949) proposed this instructive theory.
  • According to this theory antigen enter the antibody-producing cell and induce a heritable change.
  • Antigen alters the genome of the cell so that new template is formed which persist in the progeny cells (indirect template).
  •  This explained specificity and the secondary response but it was abandoned when it was known that antibodies of different specificities had different amino acid sequence in their combining sites.