Expression of latent allotypes in SJL mice

SJL mice (CH allogroup Igb) were immunized against immunoglobulins from strain BALB/c (allogroup Iga). We used either animals purchased directly from the Jackson Institute, or Jackson-derived mice which had been inbred further in our laboratory. In some mice from three independent immunization series we observed, contrary to expectation, the expression of molecules carrying allotypic determinants of Iga instead of the expected production of antibodies against these determinants. Various types of breeding experiments were carried out with parents being either "orthodox" SJL mice, or animals expressing the "wrong" allotype. Among the progeny, as analyzed so far, we again found animals which changed their allotype after antiallotypic immunization. The data do not appear to be compatible with a single-gene, dominant mendelian inheritance of allotypic determinants in this stock of mice.