Genes coding evolutionary novel anti-carbohydrate antibodies: studies on anti-Gal production in α1,3galactosyltransferase knock out mice

Abstract

This study analyzes the gene repertoire coding for antibodies to an evolutionary novel immunogenic carbohydrate antigen in mice. The α-gal epitope (Galα1–3Galβ1–4GlcNAc-R) is an autoantigen, abundantly expressed in wild type mice, but absent in α1,3galactosyltransferase knock-out (KO) mice, where it can induce the production of the anti-Gal antibody. Hybridoma clones secreting anti-Gal were isolated from different mice and their immunoglobulin genes were analyzed. All anti-Gal clones were found to be encoded by the heavy chain gene VH22.1 and light chain gene VK5.1. Moreover, one ‘forbidden’ anti-Gal clone, produced in a wild type mouse, was also encoded by VH 22.1 and VK 5.1. The genes coding for the different anti-Gal clones were found to contain somatic mutations and different CDR3 domains. These data imply that a highly restricted gene usage combined with junctional diversity and somatic mutations can generate new antibodies that have not been produced in the course of the evolution of a species.