A new perspective: molecular motifs on oxidized LDL, apoptotic cells, and bacteria are targets for chronic lymphocytic leukemia antibodies

The restricted immunoglobulin (Ig) repertoire found in B-cell chronic lymphocytic leukemia (CLL) implies a role for antigen(s) in the leukemogenesis. The nature of the antigens has, however, not been characterized, although examples of autoantigens have been demonstrated. We have analyzed a panel of 28 CLL cell lines and primary cultures, producing monoclonal Ig with different Ig heavy-chain variable region gene usage and mutational status, including several complementarity determining region 3 homology subset members. Using mass-spectrometry, immunoassays, or protein macroarrays, we have discovered novel antigens binding to CLL Igs. These antigens included cytoskeletal proteins vimentin, filamin B, and cofilin-1, but also phosphorylcholine-containing antigens (eg, Streptococcus pneumoniae polysaccharides and oxidized low-density lipoprotein [oxLDL]). Additional new antigens identified were cardiolipin and proline-rich acidic protein-1. Remarkably, these antigens represent molecular motifs exposed on apoptotic cells/blebs and bacteria, and several CLL Igs bound to apoptotic Jurkat cells. In conclusion, these intriguing data, showing a limited target structure recognition, indicate that CD5(+) CLL B cells are derived from a cell compartment that produces natural antibodies, which may be instrumental in elimination and scavenging of apoptotic cells and pathogenic bacteria.