Abstract

It is generally accepted mat in the maturation of an immune response, the quality of the antibody, as well as the quantity, will improve with time after immunization. In the mouse system, immunoglobulin obtained in the first days after immunization with NP-CGG showed greater specificity to NTP-CGG (heteroclitic specificity). While the specificity to the immunizing antigen (homoclitic specificity) was recovered few weeks later. Intensive study on its immunoglobulin structure and the sequences of its mRNA revealed that this change of specificity was due to the switch from kappa to lambda light chain rather than to the occurence of somatic hypermutation in the immunoglobulin gene. In this paper, we describe the contribution of either somatic hypermutation or immunoglobulin light chain class switch to the change of specificity from heteroclitic to homoclitic.