Marginal zone B cell enrichment and strong follicular B cell reduction correlate with a delayed IgG response in a light chain diversity restricted mouse model

Recently developed B6.κ–λSEG mice (by crossing κ– and C57BL/6 mice congenic for the wild Mus spretus SEG strain λ locus lacking genes coding for λ1 and λ3) have a very reduced light chain diversity. B6.κ–λSEG mice produce only λ2 and λx light chains. Regardless of their Igh haplotype, B6.κ–λSEG mice show a restricted B cell distribution by light chain subtype with λx dominance in all peripheral compartments except peritoneal cavity where λ2 is dominant. This distribution suggests that selection mechanisms act differently in different B cell compartments on λ2 and λx bearing B cells. Sequence analysis before or following immunization did not reveal unusual mechanisms of diversification. B6.κ–λSEG mice still respond to various challenging antigens using new Ab patterns. In particular, regardless of Igha or Ighb haplotypes, the anti‐2,4‐dinitrophenyl response is characterized by a restricted diversity for both heavy and light chains and a delayed IgG response when compared to B6 and B6.κ– mice. We suggest that the delayed IgG response is due to the expansion of marginal zone B cells whereas follicular B cells are strongly reduced.