Human Ia molecules carrying MT1 determinants: Purification with a monoclonal antibody

A monoclonal antibody 77.34, reactive with polymorphic HLA class II molecules, was produced. The allotype specificity of this IgG2a antibody was analyzed by cytotoxicity, flow cytometry, and cellular radioimmunoassay. Cytotoxic reactivity on a panel of B cells from 88 unrelated individuals was concordant with the MT1 (DC1) allospecificity (r = 0.83). Immunoanalysis by flow cytometry showed that cells from MT1⁺ homozygous cell lines were reactive, whereas MT2⁺ and MT3⁺ homozygous cells were not. A cellular radioimmunoassay performed under saturating conditions indicated that three MT1⁺ cell lines bound 14–45 × 10⁵ molecules of antibody per cell representing 30–40% of the amount detected with monomorphic anti-DR monoclonal antibody 21w4. The subset of molecules bearing the MT1 allospecificity was purified with a 77.34 IgG immunoadsorbent. The purified molecules were antigenically reactive with several antibodies directed at DQw1 molecules but were devoid of reactivity to monomorphic anti-DR antibodies. Two-dimensional gel electrophoresis showed that the subunit is composed of several acidic spots of Mr 32,000 whereas the β subunit was seen as a single spot of Mr 25,000, corresponding to DQw1 molecules. DR molecules purified by monoclonal antibody affinity were unreactive with 77.34 antibody. All of the 77.34 reactivity was observed with the fractions depleted of DR molecules. Two-dimensional gel analysis showed marked differences between the purified DR and DQw1 molecules. Two-dimensional gel analysis showed marked differences between the purified DR and DQw1 molecules. The presence of the MT1 determinant on Ia molecules referred to as the DQw1 molecules and distinct from those bearing the DR epitopes was confirmed on two DR1, MT1 homozygous cell lines. Thus, DQw1 molecules can be purified away from DR1 molecules by affinity chromatography to 77.34 IgG, specifically reactive with the MT1 (DQw1) allospecificity. The binding of 77.34 IgG to MT1⁺ cells was not inhibited by all monoclonal antibodies reported to be correlated with the MT1 allospecificity suggesting that the latter might be comprised of more than a single epitope.     

A monoclonal antibody reactive with a second epitope of the 67,000-dalton human T cell antigen

Hybridomas were produced against the T-cell CLL derived-cell line, SKW3, by the fusion of hyperimmune spleen cells with P3 myeloma cells. One clone, designated DU-SKW3-1, was shown to produce a murine IgG2b antibody reactive with an antigen expressed on normal thymocytes and peripheral blood T cells. This antigen was not detected on human B cells, erythrocytes, monocytes, granulocytes, or platelets. D-SKW3-1 also reacted with T-ALL, T-CLL, and B-CLL cells, but did not react with common ALL or acute myelocytic or monocytic leukemias. Immunoprecipitation of lactoperoxidase-iodinated, detergent-solubilized PBL demonstrated that DU-SKW3-1 reacted with a protein with an apparent mass of 67,000 daltons (p67), which had identical mobility to the antigen precipitated by L17F12, Cocapping experiments suggested that DU-SKW3-1 and L17F12 detected the same molecule: however, DU-SKW3-1 was unable to block the binding of L17F12. In addition, DU-SKW3-1 reacted with the T lymphocytes of both the great apes and old world monkeys, in contrast to L17F12 and two other p67 monoclonals, T101 and 10.2, which reacted only with the cells of the great apes. This data suggests that DU-SKW3-1 may react with a second, less phylogenetically restricted epitope on the p67 T cell-/CLL-associated molecule.     

Characterization of a human monoclonal autoantibody directed to cardiolipin/beta 2 glycoprotein I produced by chronic lymphocytic leukaemia B cells.

We determined the specificity and sequence of immunoglobulin molecules synthesized by monoclonal B cells from a patient with chronic lymphocytic leukaemia (CLL) who presented with a number of clinical and biological autoimmune symptoms. Heterohybrids obtained by fusion of CLL cells with the mouse X63-Ag 8.653 myeloma produced IgM lambda MoAbs directed to the cardiolipin/beta 2 glycoprotein I (beta 2GPI) complex and ssDNA. They were devoid of polyreactivity. Nucleotide sequence analysis of the variable domain of the mu chain indicated the utilization of the VH4 71.2 gene or one allotypic variant, DXP4 and JH3 segments. The lambda light chain used the single gene from the V lambda 8 subfamily, J lambda 3 and C lambda 3 genes. The VH gene displayed 11 nucleotide changes in comparison with its putative germline counterpart. However, these nucleotide changes correspond to variations observed in other published VH4 sequences, suggesting gene polymorphism rather than somatic mutation. DXP4 and JH3 were also in germline configuration. The VL gene exhibited a single replacement mutation in CDR1. These data suggest that the monoclonal CLL B cells in this patient retained VH and VL genes in germline configuration although they secreted a pathogenic anti-cardiolipin antibody associated with clinical symptoms, vasculitis and thrombosis, which may be provoked by antibodies to the phospholipid/beta 2GPI complex.     

Monoclonal antibodies specific for kappa chain, lambda chain, and IgG1 of human gammaglobulin

Hybrid cell lines secreting antibodies specific for human gammaglobulin (HGG) were prepared by cell fusion and cloning techniques. The monoclonal antibodies were tested for their antibody reacts with a different antigenic determinant of HGG. One reacts with isolated kappa (kappa) light chains, one with isolated lambda (lambda) light chains, and one with the Fc fragment of IgG1 molecules. The reactivity patterns of two additional monoclonal antibodies are more complex. One reacts with a determinant present on the Fc of all IgG subclasses and the other binds to a determinant on the Fab of IgG molecules. The two monoclonal antibodies reactive with light chains also bind to surface components of human B cells. The murine immunoglobulin (Ig) class of each clone product was identified.