THE REPERTOIRE OF SOMATIC ANTIBODY MUTANTS ACCUMULATING IN THE MEMORY COMPARTMENT AFTER PRIMARY IMMUNIZATION IS RESTRICTED THROUGH AFFINITY MATURATION AND MIRRORS THAT EXPRESSED IN THE SECONDARY RESPONSE

The anti-(4-hydro)cy-3-nitro-phenyl)acetyl (NP) response is dominated by λ1 chain-bearing antibodies expressing the VH gene V186.2 in combination with the D element. DFL16.1. λ1- positive B cells were isolated from the spleens of mice immunized with NP-chicken gamma globulin 6 wk earlier. Rearranged V186.2 genes were amplified from the genomic DNA of these cells and sequenced. In cases where the rearrangement was typical for secondary anti-NP antibodies, the VHDJH sequences were generally heavily mutated. The frequency and the nature of the nucleotide exchanges mirrored those of secondary response antibodies. V186.2 genes with other rearrangements and V186.2-related genes isolated concomitantly were essentially unmutated. These results demonstrate: (a) that somatic antibody mutants are largely restricted to a small compartment ofperipheral B cells, namely, that ofmemory cells; (b) that the memory compartment is strongly selected for high affinity precursors and largely purged from antigen-binding loss mutants ; and (c) that the repertoire of binding specificities expressed in the secondary response is established in its final form before secondary immunization. © 1990, Rockefeller University Press., All rights reserved.