Serological studies of actionomyces israelii by crossed immunoelectrophoresis: standard antigen-antibody system for A. israelii.

Standard preparations of crude cytoplasmic and whole cell-associated antigen mixtures of Actinomyces israelii were analyzed by crossed immunoelectrophoresis (CIE), with a standard polyvalent antiserum comprising purified and concentrated immunoglobulin G antibodies to formolized whole cells of A. israelii serotypes 1 and 2. The standard antigens provided four antigen-antibody systems for A. israelii. The immunoprecipitation patterns of the system were compared, and the immunochemical characteristics of individual precipitates were analyzed. Each system contained specific precipitates, but also one or two precipitates which were immunochemically identical to precipitates of the other systems. The standard system for A. israelii based on cytoplasmic antigens was best reproducible and revealed the highest number of immunoprecipitates. These precipitates possessed immunochemical properties which made them suitable for CIE studies. The cytoplasmic antigen mixture of A. israelii was, therefore, adopted as the most suitable for further development of a crossed immunoelectrophoretic system for A. israelii. In subsequent assays the cytoplasmic antigen mixture was raised in rabbit against cell lysates of A. israelii, serotypes 1 and 2. A standard antigen-antibody system for A. israelii was obtained which revealed an immunoprecipitation pattern of 10 distinguishable precipitates. The resolving power and separation by CIE of this standard system for A. israelii was compared with that of crossed immunoelectrofocusing. The results suggest that these methods supplement each other. Crossed immunoelectrofocusing appeared to be a useful tool for separation of specific components of the protein-antigen complex of A. israelii for analytic serology. The CIE in conjunction with a standard reference antigen-antibody system for A. israelii based on cytoplasmic antigens offers great potentialities in diagnostic A. israelii serology.