Genetic basis of the neonatal antibody repertoire: germline V-gene expression and limited N-region diversity.

We report here on the molecular characterization of heavy and light chain V-regions of antibodies isolated from the highly connected idiotypic network of the newborn BALB/c mouse. Nucleotide sequence analysis of eight hybridomas confirmed their germline origin. Furthermore, in contrast to most hybridomas and myelomas derived from adult mice, the majority of these clones were found to lack N-region sequences. These data show that somatic processes amplifying junctional diversity are relatively inactive early in ontogeny, and that germline gene expression alone ensures idiotypic complementarities in the developing immune system.