Expression of Leu M1 antigen on a monoclonal B cell line established from a patient with rheumatoid arthritis

The purpose of this study is to show that anti-Leu M1 antibody (anti-CD15), which has different staining characteristics in lymphoid and non-lymphoid cells, reacted against the surface antigen of a defined monoclonal B cell line. This antibody recognizes the sugar moiety, lacto-N-fucopentaose (LNF-III), which is linked to the cell membrane protein in several kinds of cells, but not in B cells. However, a human monoclonal B-cell line (TKS-1) which was established from the peripheral blood of a patient with rheumatoid arthritis, expressed the Leu M1 antigen spontaneously. The analysis of surface markers using a fluorescence-activated cell sorter (FACS) has revealed that the surface markers of TKS-1 were anti-mu, delta, kappa, HLA-DR, DQ, Leu 12 (CD19) and Leu M1 (CD15). TKS-1 cells were not reactive with any of the following antibodies: anti-OK M1 (CD11b), Leu M2, Leu M3 (CD14), Leu M4, Leu 1 (CD5), Leu 2 (CD8), Leu 3 (CD4), Leu 4 (CD3), Leu 7 and Leu 11 (CD16). In addition, TKS-1 was positive to Epstein-Barr nuclear antigen, weakly positive to non-specific esterase without staining inhibition by NaF, and negative to peroxidase. TKS-1 cells produced IgM in the culture supernatant and have kappa-light chain rearrangement in its DNA. As shown in other studies, distribution of Leu M1 is very wide. This antigen is not a specific immunodiagnostic marker to distinguish the cell type. We conclude that it is possible to express Leu M1 antigen on the membrane of a B-cell lineage cell.