Induction of Ig Somatic Hypermutation and Class Switching in a Human Monoclonal IgM+ IgD+ B Cell Line In Vitro: Definition of the Requirements and Modalities of Hypermutation

摘要: Partly because of the lack a suitable in vitro model, trigger(s) and mechanism(s) somatic hypermutation Ig genes are largely unknown. We have analyzed potential human CL-01 lymphocytes, our monoclonal model germinal center B cell differentiation. These cells surface IgM+ IgD+ and, absence T cells, switch to IgG, IgA, IgE response CD40:CD40 ligand engagement exposure appropriate cytokines. show here that can be induced effectively mutate expressed VHDJH-Cμ, VHDJH-Cδ, VHDJH-Cγ, VHDJH-Cα, VHDJH-Ce, VλJλ-Cλ transcripts before after class switching stepwise fashion. In these induction mutations required cross-linking receptor for Ag contact through CD80:CD28 coengagement. The showed intrinsic features V(D)J they comprised 110 base substitutions (97 heavy chain 13 λ-chain) only 2 deletions targeted V(D)J, virtually sparing CH Cλ. were more abundant secondary VHDJH-Cγ than primary VHDJH-Cμ V(D)J-C transcripts. also associated with coding DNA strand polarity an overall rate 2.42 × 10−4 changes/cell division VHDJH-CH Transitions favored over transversions, G nucleotides preferentially targeted, mainly context AG dinucleotides. Thus, is readily inducible by stimuli different from those displays discrete substitution modalities.