A Monoclonal IgM With Antibodylike Specificity for Phospholipids in a Patient With Lymphoma

Both murine and human myeloma proteins have been shown to have antibodylike activity for serum lipoproteins. We studied a 58-yr-old woman (M.L.) with a lymphoma and a VDRL titer of 1:4096 and a nonreactive FTA-ABS. Serum electrophoresis revealed an M-component which was shown to be IgM-kappa by immunoelectrophoresis and 2-mercaptoethanol treatment of the serum reduced the VDRL titer to 1:64. Immunoelectrophoresis (IEP) of the purified IgM against sonicates of the specific components of the VDRL antigen (cardiolipin, lecithin, cholesterol) produced a precipitin line with both cardiolipin and lecithin. All IgM in the serum could be removed by absorption with cardiolipin, and elution experiments demonstrated the specificity of this reaction. A quantitative precipitin test demonstrated that at the point of equivalence, 0.009 mg of antigen (cardiolipin) reacted with 0.4 mg of IgM (antibody). Additional studies showed that purified IgM (M.L.) gave a positive reaction with nine of 15 phospholipids tested. Similar studies on sera from 50 normal individuals, ten patient’s sera without M-components giving false positive VDRL reactions, and serum from one patient with a congenital absence of IgA and IgG and increased IgM showed no evidence of such a precipitin reaction with any phospholipid tested. Thus, it appeared that the IgM-kappa monoclonal protein behaved like an antibody directed against specific phospholipid antigenic components. The role of lipid antigens in the initiation of such neoplastic and immunologic abberrations should be further investigated and monoclonal proteins screened more extensively against such antigens.