Soluble T cell receptor-like properties of an HLA-B35-specific monoclonal antibody (TU165)

A mouse monoclonal antibody of IgM class (TU165) was produced using Epstein-Barr virus (EBV)-infected mutant cells derived from the human BJAB-B95.8.6 cell line as immunogen. Binding studies with several HLA deletion mutant cell lines indicated that TU165 recognized the HLA-B35 molecule. In a panel of 89 EBV-transformed lymphoblastoid cell lines, all HLA-B35+ cells (n = 24) reacted with TU165 while all but two HLA-B35- lines (n = 65) were unreactive (r = 0.95). Surprisingly, peripheral blood lymphocytes of HLA-B35+ donors were unreactive; however, strong enhancement of TU165 recognition was observed with B cells of one of these individuals after transformation with EBV (B95.8 strain). Transfection of both HLA-B35 and human beta 2-microglobulin genomic DNA into mouse P815 cells led to high expression of HLA-B molecules; yet, expression of the TU165 epitope was not observed. Furthermore, the EBV-negative cell line BJAB as well as the EBV-infected (P3HR1 strain) line BJAB-HR1K were only weakly reactive, whereas the BJAB-B95.8 cell line was strongly positive. These results indicate that EBV-encoded or -controlled peptide(s) must be bound by HLA-B35 antigens to create the epitope which allows efficient binding of TU165.

Evolution of a CD3+CD4+ alpha/beta T-cell receptor+ mature T-cell clone from CD3-CD7+ sorted human bone marrow cells

In order to study extrathymic differentiation in vitro, CD7+CD3- lymphocytes were sorted from normal human bone marrow and cultured under conditions of limiting dilution together with irradiated pooled allogeneic peripheral blood mononuclear cells (PBMC) and phytohemagglutinin (PHA) in the presence of 1000 U/ml of interleukin-2 (IL-2). One clone was obtained that failed to react with monoclonal antibody (mAb) TCR delta 1 (TCR1, gamma/delta-specific) or WT31 (TCR2, alpha/beta-specific). From day 35 through day 74 in culture, the surface phenotype of this clone evolved into CD3+, CD4+, CD8-, TCR2+, TCR1-, and was further characterized as CD2+, CD45RO+, CD16-, and CD56-. The presence of mRNA for TCR alpha and beta but not gamma and delta chains was confirmed by Northern blotting. Accessory cell-dependent autocrine proliferative responses to PHA (most likely driven by IL-2) were initially absent, but became measurable at the same time as the TCR was acquired. However, in the absence of PHA, the clone failed to respond to a panel of homozygous B-cell lines representing the majority of MHC class II alleles. Autoreactivity was also not demonstrable. Cytotoxicity was limited to MHC unrestricted "natural killer (NK)-like" lysis of K562 target cells, with no autocytotoxicity detected. The NK-like lysis diminished over time in parallel with the acquisition of surface TCR. The cloned cells were not suppressive for mature lymphocyte proliferation. After stimulation, the cells secreted tumor necrosis factor alpha and granulocyte/macrophage colony-stimulating factor (GM-CSF) detected by immunoassays, and T-cell growth factors, most likely IL-2, as detected by bioassays. Polymerase chain-reaction methods demonstrated the presence of mRNA for IL-2, IL-3, IL-4, IL-9, interferon-gamma, and GM-CSF in these cells after stimulation with PHA and B-LCL. These results suggest that cells with the phenotype and some functional characteristics of mature T lymphocytes can evolve extrathymically in vitro from T-cell precursors sorted from normal human bone marrow.

Separation and purification by two-dimensional gel electrophoresis of a 52-54 kDa bumetanide binding protein from rat liver plasma membranes

By affinity labeling with photolabile [3H]bumetanide, a 52-54 kDa bumetanide binding protein was identified in the sinusoidal plasma membrane fraction from rat liver. The protein is assumed to represent the carrier for hepatic uptake of loop diuretics. By two-dimensional (2D) gel electrophoresis we have purified this protein from hepatocytes, sinusoidal plasma membranes and subfractions of associated and integral plasma membrane proteins. Amongst more than 20 protein spots, a single integral plasma membrane protein was detected. The apparent pI of this molecule is 6.7. Specific labeling of this protein was not found in the fraction of associated plasma membrane proteins. To detect possible binding of radioactive bumetanide to microsomal cytochrome P450s, photolabeling experiments with integral plasma membrane proteins were performed under nitrogen/carbon monoxide atmosphere and in the presence of piperonyl butoxide. Labeling of the 52-54 kDa protein was not affected by these inhibitors of P450 enzymes. Taken together, these results indicate that the bumetanide binding protein is very likely to be a non-microsomal integral plasma membrane protein.

The effects of the antifungal azoles itraconazole, fluconazole, ketoconazole and miconazole on cytokine gene expression in human lymphoid cells

The antifungal azole drugs itraconazole (itra; R51,211), fluconazole (flu; UK-49,858), ketoconazole (keto) and micronazole (mico) have been investigated for their suppressive influence on the gene expression of the immunoregulatory cytokines IL2, IL4, IL9, GM-CSF, TNF-alpha, IFN-gamma, as well as both chains of the IL2 receptor in human PBMC and of the cytokines in the human keratinocyte cell line HaCat 17.5. The results obtained in Northern blot analysis were compared with the effects of the established immunosuppressant drug CSA and the new immunosuppressive drug FK 506, as well as the cytokine TGF-beta, which is also immunosuppressive. While 1 microgram/ml CSA and 0.1 microgram/ml FK 506 completely suppressed PHA-stimulated accumulation of mRNA for IL2, IL4, IL9, GM-CSF, TNF-alpha and IFN-gamma in PBMC, flu, keto and TGF-beta failed to inhibit any (except TNF-alpha blocked by TGF-beta). Itra and mico did suppress accumulation of mRNA, but unlike CSA and FK 506, only at high doses (10 micrograms/ml) and after extended incubation (24 h). None of the drugs nor TGF-beta suppressed the expression of the IL2R-alpha and IL2R-beta genes or TNF-alpha-stimulated cytokine gene expression in keratinocytes. Itra and mico, 1 mg/ml (achievable serum level), caused only slight inhibition of the cytokines in PBMC after 6 and 24 h of incubation. These results demonstrate that the mode of action of the azoles is different from CSA and FK 506.(ABSTRACT TRUNCATED AT 250 WORDS)

Photoaffinity labeling of plasma membrane proteins involved in the transport of loop diuretics into hepatocytes

To identify proteins involved in the hepatocellular uptake of loop diuretics, [3H]bumetanide was photoactivated by light flash in the presence of either intact isolated rat hepatocytes, rat liver basolateral plasma membranes or integral membrane proteins extracted from the basolateral plasma membranes. Proteins of 52-54, 48, 33, 27, 25 and 23 kDa in sodium dodecyl sulfate (SDS) gel electrophoresis were radiolabeled on intact hepatocytes. On liver basolateral plasma membranes a 50-52 kDa protein was the most intensely labeled protein. After separation into integral and associated membrane proteins by extraction with Triton X-114, radioactive labeling was only found in integral membrane proteins with a molecular weight of 50-52 kDa. Photoactivated bumetanide irreversibly inhibited the hepatocellular uptake of cholate, taurocholate but not of serine. Binding proteins for photoactivated bumetanide were absent on AS 30-D ascites hepatoma cells. Labeling of all proteins was sodium dependent in intact hepatocytes but was sodium independent in plasma membranes. Labeling was prevented by non-labeled bumetanide and by the loop diuretics piretanide and furosemide. Labeling protection was further achieved with organic anions such as bromosulfophthalein, rifampicin, probenecid and by the bile acids taurocholate, deoxycholate and dehydrocholate. The radiolabeled proteins did not belong to the bumetanide-sensitive NaCl/KCl co-transport system which apparently does not occur in intact isolated rat hepatocytes.

Immunopathology of cutaneous human lupus erythematosus defined by murine monoclonal antibodies

Skin biopsy specimens obtained from involved skin from sixteen patients with systemic and discoid lupus erythematosus were studied. Murine monoclonal antibodies with a biotin-avidin-horseradish peroxidase staining system were used. The findings consisted of a marked reduction in the number of epidermal Langerhans cells defined by surface antigens, reduced HLA-DR (Ia-like) antigens on the surface of dermal capillary endothelium, and mononuclear cell infiltrates characterized by a predominance of helper T lymphocytes and an increase in the number of mononuclear phagocytic cells. B lymphocytes were rarely identified. The number of T lymphocytes within the dermis correlated inversely with both the number of HLA-DR-positive epidermal Langerhans cells (p less than 0.01) and the HLA-DR staining of dermal capillary endothelium (p less than 0.01). These findings suggest that a T lymphocyte-mediated immune response associated with a reduction in Langerhans cells and capillary endothelium HLA-DR antigens is involved in the inflammatory process of lupus erythematosus skin.