Germ-line origin of functional idiotypic interactions: identification of two idiotypically connected, natural antibodies that are encoded by germ-line gene elements.

Two monoclonal, natural IgM antibodies derived from normal BALB/c mice were selected on the basis of being idiotypically complementary and functionally connected. Nucleotide sequence analysis of their respective heavy and light chain V regions showed that both of the clones expressed VH, D, JH, VL and JL gene segments of germ-line origin. Furthermore, none of the clones displayed N-sequence additions. These data suggest a germ-line origin of a functional idiotypic network and confirm a minimized contribution of somatic diversification through template-independent addition of N-nucleotides in neonatal B cell repertoires.