Autoantibodies to Phosphatidylcholine

: The observation that murine B-cell populations can contain relatively large numbers of cells that produce IgM with the ability to lyse bromelain-treated mouse erythrocytes (BrMRBC), but not normal untreated MRBC, was made nearly 20 years ago. The major observations regarding the antigen specificity, the cells that produce this IgM, and the immunoglobulin V genes that encode them are summarized in this report. The epitope on BrMRBC that is recognized has been identified as the head group of phosphatidylcholine (PtC); B cells whose IgM has this specificity can be easily identified by their ability to bind fluorescent synthetic liposomes whose membrane contains PtC. The cells producing IgM specific for PtC all derive from the Ly-1 B-cell subset, and they use primarily two VH/VL gene pairs to encode the anti-PtC antibodies. The VH genes used describe two new VH gene families, VH11 and VH12. The genes encoding anti-PtC are unmutated and have characteristics and restricted VDJ constructions. The cells with this specificity, within individual mice, are polyclonal. These criteria are consistent with a primary antigen-driven clonal selection mechanism as the basis for the development of this immune specificity.