Neutral glycosphingolipid expression in B-cell neoplasms.

The expression of neutral glycosphingolipids (GSL) in 37 B-cell neoplasms [7 acute lymphocytic leukemia (ALL), 5 Burkitt's lymphoma (BL), 7 chronic lymphocytic leukemia (CLL), 5 diffuse, poorly differentiated lymphoma (DPDL), 6 diffuse histiocytic lymphoma (DHL), 3 hairy-cell leukemia (HCL), and 4 multiple myeloma (MM)] was examined. Patterns of expression of simple (GlcCer, LacCer) and globo-series GSL (Gb3, Gb4) were found for each tumor type. In addition, pre-B ALL expressed the neo-lacto series GSL, paragloboside, which was not significantly seen at later stages of maturation. As a group, leukemias expressed about 10 times higher ratios of simple GSL to Globo-series GSL as compared to lymphomas, regardless of stage of differentiation. Significant amounts of GSL of other series were not found except in one CLL which contained asialo-GM2. GSL phenotype in these cells was not grossly affected by cell genotype since pre-B ALL containing Philadelphia chromosome t(9q;22q) translocations were similar to other ALL; and DHL with t(8q;14q) translocations had GSL patterns similar to other DHL samples and dissimilar to GSL patterns found in Burkitt's lymphomas with t(8q;14q). Differences in GSL expression among the different types of B-cell neoplasm suggested that GSL patterns form a phenotypic map that may complement the traditional glycoprotein immunophenotypic map and contribute to our understanding of the biology of these diseases and B-cell differentiation.

Inhibition of cell proliferation with an HLA-A-specific monoclonal antibody.

A new mouse IgG2A monoclonal antibody--JD 12--is described, which was selected for its ability to inhibit peripheral blood mononuclear cell (PBMC) proliferation. Serologic, immunoprecipitation and immunoelectrophoretic studies showed JD12 to be monomorphically reactive with HLA-A molecules with an affinity of 10(9) M-1. JD12 was capable of inhibiting growth in resting or stimulated PBMC with an ID50 of 300 ng/ml in a time-dependent and dose-dependent manner without cytotoxicity. IgG, F(ab)2 and F(ab) were active. Growth stimulation by phorbol ester was not inhibited, suggesting that JD12 action occurred prior to protein kinase C activation. DNA and RNA synthesis were both slowed with a resulting G0/G1 block. Analysis of separated PBMC components showed that adherent cells displayed increased activity (clumping and RNA synthesis) upon JD12 binding. In addition, the inhibitory activity of JD12 could be transferred to new cultures by cell-free, IgG-free supernatant from JD12-treated PBMC, suggesting that the antiproliferative effects could be mediated, at least in part, in an indirect manner through an inhibitory factor. Therefore, potent, noncytotoxic inhibition of cell proliferation, DNA and RNA synthesis via MHC molecules can be mediated specifically through effects initiated by binding to HLA-A molecules alone.

A monoclonal antibody for terminal beta-galactose. Use in analysis of glycosphingolipids.

A monoclonal antibody (mAb 8281) specific for the terminal beta-galactose (beta Gal) of glycosphingolipids (GSL) and glycoproteins was produced from mice immunized with lipid extract from fresh acute lymphocytic leukemia (ALL) cells. Immuno-thin layer chromatography (ITLC) and competition assays with purified neutral GSL standards, free sugars, and synthetic neoglycoproteins showed mAb 8281 to be strongly reactive with LacCer, GalCer and Gal-beta-O-(CH3)2S(CH3)2-CONH-(Gal-beta-O-CETE) linked to bovine serum albumin (BSA). The penultimate sugar also played a role in binding. The antibody was not reactive with carbohydrates with terminal alpha Gal structures and unrelated terminal moieties. Indirect immunoperoxidase staining and flow cytometry with mAb 8281 demonstrated positive staining on numerous tissues, including smooth muscle, gastrointestinal mucosa, lymph node B cells and monocytes. ITLC analysis of the GSL composition of fresh B cell neoplasms using mAb 8281 confirmed the presence of lactosylceramide and galactosylceramide in neoplasms of varying stages of differentiation. Because of its specificity for terminal beta Gal carbohydrate residues, mAb 8281 may be useful in structural and functional analyses of GSL.