The selection and maintenance of the V region determinant repertoire is germ-line encoded and T cell-independent.

The number of lipopolysaccharide-sensitive precursor cells synthesizing immunoglobulin (Ig) which reacts with the monoclonal anti-M460 antibody F6(51) has been determined in the spleen and in the bone marrow of different strains of mice. These precursor frequencies fall into two quantitatively different groups. The first group includes mice with the same Igh haplotype as BALB/c animals (Igha). In this group, spleen cells contained between 1:10(4) to 1:5 X 10(4) B cell precursors secreting Ig which bound F6(51). The second level of precursor was obtained with animals with allotypic haplotypes other than Igha. These values were too low to allow accurate frequency determinations. The frequency of these cells in mice of the latter group, however, increased dramatically when these animals were hyperimmunized with the monoclonal anti-M460 antibody. Similar results were obtained when the frequencies were determined using the Ig- fraction of bone marrow cells. Surprisingly, the numbers of lipopolysaccharide-sensitive B cell precursors secreting F6(51)-binding Ig in spleen cells of nude mice was found to be similar to the one in splenocytes of normal mice, and even in this case, the frequencies reflected the genetic background of the animals tested. Taken together these data support the notion that the establishment and the maintenance of the M460 idiotypic repertoire is germ-line encoded and independent of regulatory T cells.