Evolutionary conservation of a gene which controls the VH regions of an anti-hapten antibody (NP).

Wild mice of eight types were immunized with hapten NP, and the occurrence of a genetically controlled idiotype NP-b in their sera was studied. Five of the mouse types were subspecies of Mus musculus, the others were M. cervicolor, M. dunni and M. caroli. An idiotype indistinguishable from NP-b was the prediminant anti-NP antibody in M. m. molossinus, the other seven types of mice did not have this antibody population. Lack of the idiotype in these mice does not show that they do not have the VH gene controlling its expression since the idiotypic population must have the lambda light chain, and the seven types of mice either have little of lambda immunoglobulin or have lambda chains different from the lambda chains of the laboratory mice.