Primary and secondary immune responses The primary immune response occurs on initial contact with a foreign antigen and results in production of immunoglobulin M and then IgG. If the same antigen is encountered again, immunological memory leads to a secondary immune sponse that produces a much more rapid and larger increase in specific IgG production
Primary and secondary immune responses • The primary immune response occurs on initial contact with a foreign antigen and results in production of immunoglobulin M and then IgG. • If the same antigen is encountered again,immunological memory leads to a secondary immune rsponse that produces a much more rapid and larger increase in specific IgG production
Primary and secondary immune responses PRIMARY RESPONSE SECONDARY RESPONSE Total antibody-Plateau Decline 15 days 10 days 15 days First exposure econd exposure to antigen (→ Plasma cell ( B cells ◎+ ◎→◎ o→◎◎→◎ ◎+-0-0 O+◎+0
Primary and secondary immune responses
Clonal selection theory A large number of antibody-producing cells exist in an animal even before it encounters a foreign antigen, each cell producing only one specific antibody and displaying this on its cell surface. An antigen binds to cells that display antibodies with appropriate binding sites and causes proliferation of those cells to form clones of cells secreting the same anti body in high concentration
Clonal selection theory • A large number of antibody-producing cells exist in an animal even before it encounters a foreign antigen, each cell producing only one specific antibody and displaying this on its cell surface. An antigen binds to cells that display antibodies with appropriate binding sites and causes proliferation of those cells to form clones of cells secreting the same antibody in high concentration
Clonal selection Antigen receptor Antigen 有 Variety of B cells Cell proliferation Clone of plasma cells Clone of memory cells 上 Antibodies secreted into circulation Copynghto Pearson Education, Inc publishing as Benjamin Cummings
Clonal selection
Self-tolerance Cells that produce antibody that reacts with normal body com ponents are killed early in fetal life so that the adult animal normally is unable to make antibodies against self, a condition called self-tolerance
Self-tolerance • Cells that produce antibody that reacts with normal body components are killed early in fetal life so that the adult animal normally is unable to make antibodies against self, a condition called self-tolerance