Somatic diversification of S107 from an antiphosphocholine to an anti-DNA autoantibody is due to a single base change in its heavy chain variable region.
The S107 myeloma cell line expresses the germ-line sequence of the T15 antiphosphocholine (P-Cho) antibody, which is the major antibody made by BALB/c mice in response to P-Cho, either on a variety of bacterial polysaccharides or when attached to a protein carrier. We have previously reported that a somatic mutant of the S107 cell line produces an antibody that has lost the ability to bind P-Cho and has acquired binding for double-stranded DNA. This antibody has a substitution of an alanine for a glutamic acid at residue 35 in the heavy chain variable region. We now show that this amino acid substitution is due to a single A-C transversion, which is the only nucleotide change in the heavy and light chain variable regions. Further, it appears that this change is due to somatic mutation rather than to gene conversion.
D000818:Animals; D001323:Autoantibodies / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D002794:Choline / Q000031:analogs & derivatives*; D004273:DNA, Neoplasm / Q000276:immunology*; D014644:Genetic Variation; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D009693:Nucleic Acid Hybridization; D010767:Phosphorylcholine / Q000276:immunology*; D010954:Plasmacytoma / Q000276:immunology*
D001323:Autoantibodies; D004273:DNA, Neoplasm; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D010767:Phosphorylcholine; D002794:Choline