Cascade immunization: a method of obtaining polyspecific antisera against crude fractions of antigens.

Between 20 and 30 precipitation lines are usually obtained by crossed immune electrophoresis of an Escherichia coli cytoplasmic extract against antisera produced against that extract in individual rabbits. With a combination of several such antisera, the number of precipitation lines increases to 30-40. Nevertheless, extracts as used in this work contain many antigens in addition to those thus detected. Intermolecular immune competition may be avoided by removing strong immunogens from the extracts. The remaining antigens which give no immune response in the primary immunization are used for further immunization. New antibody production against 8-14 additional antigens occurs after one such 'cascade immunization' step. Separation of strong from weak immunogens is performed by preparative CIE and the use of immuno-affinity columns. The procedure is called cascade immunization because it involves repeated removal of antigens and production of further antisera directed against antigens in the remainder.