Somatic mutation of the T15 heavy chain gives rise to an antibody with autoantibody specificity.

Abstract

The S107 IgA .kappa.-chain myeloma cell line makes an antiphosphocholine antibody of the T15 idiotype. A somatic mutant of this line, U4, makes an Ig with a single amino acid substitution of Ala for Glu at residue 35. This single amino acid change results in a loss of phosphocholine binding activity. The U4 Ig has reactivity with a variety of phosphorylated macromolecules, including double-stranded DNA, protamine and cardiolipin. Thus, a single amino acid change in the T15 H-chain can transform an antibacterial antibody into an antibody that resembles the autoantibodies seen in mice and man with autoimmune disease.