Quantitative Investigations of I D I O T Y P I C Antibodies Vi. Idiotypic Specii~icity as a Potential Genetic Marker for the Variable Regions of Mouse Immunoglobulin Polypeptide

Myeloma proteins (1) and antibodies of a given specificity (2, 3) produced in an individual animal possess individually specific or "idiotypic" (4) antigenic determinants. 1 Idiotypic cross-reactions among antibodies of the same specificity from different individual rabbits or humans are infrequent (2, 3, 5, 6) and are generally weak when they do occur (7). Eichmann and Kindt (8), however, recently reported strong cross-reactions among the antistreptococcal antibodies of some of the rabbits of a family group. These rabbits were descended from a brother-sister mating pair selected on the basis of production of antibodies of limited heterogeneity in response to streptococcal cell wall antigens. There is evidence that idiotypic cross-reactions may be more frequent among mice of an inbred strain than among rabbits. Cohn et al. (9) prepared antiidiotypic antibodies in an A/J mouse against a BALB/c myeloma protein with antibody-like activity against pneumococcal C carbohydrate. Antisera to C carbohydrate prepared in 6 of 10 normal BALB/c mice formed precipitates with the antiidiotypic antiserum in the Ouchterlony test. The intensities of the precipitin lines were weaker with the cross-reacting sera than with the myeloma protein used as immunogen and lines of identity were not demonstrated. In addition, idiotypic cross-reaction was noted with another myeloma protein with anti-C carbohydrate activity. Potter and Lieberman (10) examined eight BALB/c myeloma proteins which bind phosphorylcholine and found that five share idiotypic determinants, giving lines of identity in the Ouchterlony test. The present investigation was designed to provide quantitative information