Induction of histidine decarboxylase by dexamethasone in mastocytoma P-815 cells

Dexamethasone at a concentration as low as 10 nM significantly increased both the histamine content and histidine decarboxylase activity of cultured mastocytoma P-815 cells. Both effects were clearly seen using several glucocorticoids, which were as effective as dexamethasone. In contrast to that of histamine, the serotonin level of mastocytoma P-815 cells was decreased by treatment with dexamethasone. The dexamethasone-induced increases in histamine content and histidine decarboxylase activity were completely suppressed by the addition of cycloheximide and actinomycin D. Mastocytoma P-815 cells were found to possess binding sites for [3H]dexamethasone in the cytosol (Kd = 15.7 nM) and the nuclei (Kd = 1.26 nM). These results show that glucocorticoids significantly stimulate de novo synthesis of histidine decarboxylase.     

Ca2+ transport through lipid membrane by diastereomer cyclic octapeptides

Effects of the nature and orientation of a side chain in cyclic octapeptides on Ca2+ transport were examined by using cyclo[L-Lys(Z)-Sar-L-Leu-Sar]2 (C8-L), cyclo[L-Lys(Z)-Sar]4 (C8KS), and their diastereomer cyclic octapeptides, cyclo[L-Lys(Z)-Sar-D-Leu-Sar]2 (C8-D) and cyclo[L-Lys(Z)-Sar-D-Lys(Z)-Sar]2 (C8Kk). All these cyclic octapeptides were found to take a single conformation in CDCl3, and the conformation was C2-symmetric for C8-L and C8-D, and C4-symmetric for C8KS and C8Kk. They formed a complex with Ca2+. Upon complexation, C8KS accompanied isomerization of peptide bonds, but C8-D retained the arrangement of peptide bonds. The amount of Ca2+ extracted from an aqueous solution to a chloroform solution by all L cyclic octapeptide C8-L or C8KS was about twice that of Na+, but 6-8-fold smaller than that by C8-D or C8Kk including D units. These cyclic octapeptides were capable of transporting Ca2+ through a lipid membrane above the phase transition temperature, and the transport rate decreased in the order of C8Kk-C8KS greater than C8-D greater than C8-L.     

Effects of phorbol ester and teleocidin on Ca2+-induced fusion of liposomes

The effects of different types of lipid membrane defects on Ca2+-induced fusion of liposomes containing phosphatidylserine (PS) were investigated using fluorescent probes. Teleocidin enhanced the fusion of phospholipid vesicles in an assay system using terbium/dipicolinic acid during mixing of internal aqueous phases of vesicles upon fusion. 12-O-Tetradecanoylphorbol-13-acetate (TPA) suppressed the fusion. This latter phenomenon was also observed by measuring the excitation energy transfer. The promotion of membrane fusion by teleocidin was ascribed to dehydration of the membrane surface, the suppressive effect of TPA to desorption of Ca2+ from the membrane surface. Thus, Ca2+-induced fusion of PS vesicles was shown to be sensitive to defects of the membrane surface, but insensitive to defects of the hydrophobic core of the lipid membrane.     

Activity of recombinant human alpha interferon against influenza virus infection in mice

The in vivo antiviral activity of recombinant human leukocyte hybrid interferon, HuIFN-alpha AD, was examined. Results showed that this material in highly purified form did not protect mice against a lethal dose of influenza virus, although administration of natural MuIFN-alpha/beta to mice infected with a lethal dose of influenza virus had a marked protective effect. The effect of alveolar macrophages treated with IFN on influenza virus replication was examined in vitro. The antiviral activity of alveolar macrophages treated with HuIFN-alpha AD was lower than that of MuIFN-alpha/beta. It is concluded that HuIFN-alpha AD is effective in direct inhibition of influenza virus, but not in indirect inhibition mediated by alveolar macrophages or in protection of mice from influenza virus infection.     

Inhibition of virus multiplication by immunoactive peptides

In the present study we show that peritoneal macrophages obtained from the mice treated with the immunoactive peptides inhibit the multiplication of Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), but not that of vesicular stomatitis virus (VSV), and that the intraperitoneal administration of the peptides suppresses the infection with HSV-1 in mice.     

Activation of murine T cells by streptococcal pyrogenic exotoxin type A. Requirement for MHC class II molecules on accessory cells and identification of V beta elements in T cell receptor of toxin-reactive T cells

We investigated the mechanisms of murine T cell activation by streptococcal pyrogenic exotoxin type A (SPE A), focusing on the role of MHC class II molecules on accessory cells (AC) and V beta usage in alpha beta TCR of SPE A-reactive T cells in comparison with staphylococcal enterotoxin B-reactive T cells. L cells transfected with I-Ab genes functioned as effective AC for SPE A-induced responses by C57BL/6 T cells, proliferation, and IL-2 production, but control L cells were not effective AC. Anti-I-Ab mAb inhibited the SPE A-induced responses. Staphylococcal enterotoxin B-induced C57BL/6 T cell blasts were composed of cells bearing V beta 3, members of the V beta 8 family, and V beta 11. Most of the SPE A-induced T cell blasts (about 80%) bore V beta 8.2. mAb reactive to V beta 8.2 markedly inhibited SPE A-induced T cell responses. Apparently, SPE A activates mainly T cells bearing V beta 8.2 in physical association with MHC class II molecules expressed on AC. We also discuss the pathogenic activities of SPE A in relation to toxic shock syndrome.     

Activation of murine T cells by toxic shock syndrome toxin-1. The toxin-binding structures expressed on murine accessory cells are MHC class II molecules

Toxic shock syndrome toxin-1 (TSST-1)-binding structures present on murine lymphoid tissues were investigated by using 125I-TSST-1. T-depleted C57BL/6 spleen cells incubated with TSST-1 for 3 h at 0 degree C were mitogenic to splenic T cells, indicating that the former cells bind and present TSST-1 to T cells. TSST-1-binding activity was observed in C57BL/6 splenic B cells and L cells transfected with I-Ab genes, but not in splenic T cells and control L cells. Scatchard plot analysis showed that these B cells and transfectants bound TSST-1 with similar binding affinity. SDS-PAGE analysis showed that lysates of C57BL/6 spleen cells and the I-Ab-positive transfectants contain a single band which bound TSST-1 and comigrated with I-Ab heterodimers. TSST-1-binding activity observed clearly in C57BL/6. BALB/c, and C3H/HeN spleen cells and L cells transfected with I-Ab or I-Ak genes was not reduced by paraformaldehyde fixation. Binding of 125I-TSST-1 to the three spleen cells was markedly reduced by anti-I-A antibodies, but not by anti-I-E antibodies. C57BL/6, C3H/HeN, and (C3H/HeN x C57BL/6) F1 T cells were activated by TSST-1 to proliferate and produce IL-2 in the presence of FT6.2 cells, LT1-30-3 cells and either of them, respectively, but not in the presence of control L cells. These results indicate that I-A molecules function as the structures via that accessory cells directly bind TSST-1 on the cell surface and present a triggering signal of TSST-1 to T cells.     

Induction of interleukins by mycoplasma in culture of human mononuclear leukocytes

Mycoplasma shows a variety of effects on immune system, including the activation of macrophage, the increase in T cell cytotoxicity, and the enhancement of the proliferation and maturation of B cells, etc. As it is well known that many cytokines regulate the immune system, it is interesting to examine whether or not human peripheral blood mononuclear cells (PBMC) produce interleukin (IL) in response to mycoplasmas. In the present study, human PMBC were incubated with 7 species of mycoplasmas for 48 hours, and IL-1 beta, IL-2 and IL-6 activities in the supernatants were determined by ELISA. All the species of mycoplasmas were able to induce IL-1 beta and IL-6, although IL-2 was induced only by M. pneumoniae. These results suggest that the influence of mycoplasma infection on immune system may be partly due to the interleukins induced by mycoplasmas.