Inheritance of an idiotype associated with the immune response of inbred mice to phosphorylcholine

Inbred mice immunized with the pneumococcal C carbohydrate produce plaque‐forming cells directed exclusively against the phosphorylcholine determinants of this antigen. The antibody responsible for plaque formation is of restricted heterogeneity with respect to its affinity for phosphorylcholine. Mouse anti‐serum directed against an idiotype shared by certain BALB/c anti‐phosphorylcholine plasmacytoma proteins specifically inhibits the formation of approximately 70% of the plaques induced by the C‐carbohydrate in BALB/c mice. The expression of this idiotype, as revealed by inhibition of plaque formation, occurs in the phosphorylcholine specific immune responses produced by mice of some inbred strains, but not of others, and shows dominant inheritance. By means of a backcross experiment, the inheritance of idiotype was shown to be determined by a gene linked to the chromosome carrying the mouse heavy chain allotype locus. In addition, the backcross data suggested the participation of a second, independently segregating gene in the determination of idiotype. Experiments with congenic mouse strains indicated that this second gene may be H‐2 linked. These observations support the hypothesis, suggested from studies on BALB/c plasmacytoma proteins, that the variable regions of mouse anti‐phosphorylcholine antibodies are specified by germ‐line genes.