Recurrent idiotopes and internal images.

A rabbit was immunized with rabbit immunoglobulins of a different allotype. The anti-allotypic antibodies produced by this rabbit were used to immunize a second rabbit which produced anti-idiotypic antibodies. To explain the occurrence, among these anti-idiotypic antibodies, of "internal images" of the original immunizing allotype, a restricted and a more general hypothesis are developed. The first assumes that B-cells can be triggered when idiotopes on their receptor molecules are recognized by the paratopes of the immunizing antibody. The second denies the existence of a specially constructed combining site on the variable domain of an antibody molecule.