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Biomedical subjects

B R Bloom

Publications and source records attributed to B R Bloom.

At least 199 records · Page 11Linked to original sources
PubMed1983

Natural killer cell activity is closely associated with a growth-inhibitory serum protein with protease-like activity.

A correlation between natural killer (NK) cell activity and growth inhibition (GI), as measured in an in vitro assay with B16 melanoma cells, mediated by a serum growth-inhibitory factor (GIF), among various strains of mice has been demonstrated. Beige mice (bg/bg), known to express low NK-activity, were also low in GIF activity and showed increased susceptibility to both B16 melanoma cells and another solid tumor (Lewis lung carcinoma) in vivo. In vivo treatment with various protease inhibitors that reduced NK-activity, also reduced growth inhibition mediated by GIF. Protease inhibitors that did not affect NK-activity did not affect GIF either. All of 4 B16 melanoma clones selected against GIF in vitro and resistant to GIF showed both resistance to NK-cells in vitro and increased growth potential in vivo. However, P-815, an NK-resistant cell line, was sensitive to GIF.

Animals↗
PubMed1982

Genetic analysis of the role of cAMP in mediating effects of interferon.

The effects of interferon (IFN) on Fc receptor-mediated phagocytosis, intracellular cAMP levels, antiviral activity, and growth inhibition were analyzed in a cloned macrophage-like cell line, J774.2, and variants derived from it. Purified IFN increased Fc receptor-mediated phagocytosis in J774.2 cells, and in cAMP-responsive nonphagocytic variants but was without effect in cAMP-unresponsive nonphagocytic variants, in adenylate cyclase-deficient variants, and in cAMP-dependent protein kinase-deficient variants. Under conditions in which IFN augmented phagocytosis, it increased intracellular levels of cAMP. Parental cells were highly sensitive to IFN-mediated growth inhibition. In contrast, cAMP-dependent protein kinase-deficient variants were only 1/100th as sensitive to growth inhibition by IFN. All cell lines tested, both responsive and unresponsive to cAMP, were equally protected by IFN against infection with vesicular stomatitis virus, demonstrating that the antiviral state was independent of cAMP. These results indicate that, in transformed macrophages, stimulation of phagocytosis and inhibition of growth by IFN are mediated through intracellular cAMP, whereas the antiviral state induced by IFN is independent of cAMP.

Adenylyl Cyclases↗
PubMed1982

Reconstitution of a variant macrophage cell line defective in oxygen metabolism with a H2O2-generating system.

A variant clone, C3C, derived from the cloned macrophage cell line J774.16 lacks the capacity to produce O2- or H2O2 after appropriate stimulation. When the parental and variant cell lines were infected with epimastigotes of Trypanosoma cruzi, the parasites were killed or their growth was inhibited by the parental line, but they grew readily in the variant clone C3C. It was possible to reconstitute the variant cell line with an enzyme system targeted to the lysosomal compartment capable of generating a single oxygen metabolite, H2O2. This was accomplished by allowing the cells to phagocytize zymosan particles covalently coupled with glucose oxidase (GO-Zy particles). Approximately one-third of the H2O2 theoretically expected to be produced by the ingested GO-Zy particles could be detected outside the cells by the cytochrome c peroxidase assay; this fraction may represent the efficiency of extracellular assays for H2O2 production. When T. cruzi-infected clone C3C cells were reconstituted with GO-Zy particles, upon addition of glucose, intracellular killing of the parasites occurred. It was possible to estimate the level of H2O2 production required to kill a single parasite (8.7 x 10(-7) nmol/min) by GO-Zy particles in suspension and to formulate a first approximation of the killing potency of the reconstituted cells--i.e., number of parasites expected to be killed--that correlated well with the observed growth of the parasites intracellularly.

Animals↗
PubMed1982

Genetics of murine resistance to Trypanosoma cruzi.

Resistance to the protozoan parasite Trypanosoma cruzi is governed by multiple genetic factors, including at least one coded for by a locus in or near the major histocompatibility complex of the mouse. The influence of the H-2 locus on resistance was evident when H-2 congenic mice on a strain background of intermediate resistance were challenged or when the survival of H-2 typed F2 mice was followed. The H-2k haplotype of the susceptible C3H/An strain was associated with higher mortality when compared with the H-2b haplotype of the resistant C57BL/10 strain. Genetic studies showed that resistance was a dominant trait and increased with genetic heterozygosity. F1 mice derived from crosses between resistant and susceptible strains, or even between two susceptible strains, were much more resistant than either parent. Crosses between two resistant strains, C57BL/6J and DBA/2J, led to resistant progeny in the F1 and F2 generations; but when recombinant inbred strains derived from these parental strains were challenged, susceptible strains were identified, indicating that different genes were responsible for resistance in the two strains.

Animals↗
PubMed1982

Role of macrophage oxidative metabolism in resistance to vesicular stomatitis virus infection.

The role of oxygen metabolites in mediating virucidal activity was studied in two cloned macrophage-like cell lines. The parental cell line, J774.16, upon appropriate stimulation with either phorbol myristate acetate (PMA) or aggregated immunoglobulin, is induced to oxidize glucose via the hexose monophosphate shunt and produce O2- and H2O2. A variant derived from it, clone C3C, is defective in oxidative metabolism and cannot be stimulated to produce O2- or H2O2. Significant differences in yields of vesicular stomatitis virus (VSV) between stimulated clone 16 cells and unstimulated cells could be obtained only when low multiplicities were used for infection. Under the same conditions, PMA stimulation of the variant clone C3C produced no reduction in yields. The effect of PMA on virus yields in clone 16 was short-lived and dose dependent. PMA stimulation of either cell line had no effect on the number of infectious centers, suggesting that the antiviral effect was likely to be an extracellular, rather than an intracellular, one. Using glucose oxidase plus aglucose to generate H2O2 in solution, we observed that H2O2 alone is capable of killing limited amounts of VSV. The inactivation of VSV, both by H2O2 in solution and by activated clone 16 cells, could be inhibited by catalase. We conclude that intracellular resistance to VSV is primarily mediated through nonoxidative mechanisms, since activated macrophages can kill only a limited number of infectious virus particles extracellularly by means of secreted H2O2.

Cell Line↗
PubMed1982

Studies on the mechanism of NK cell lysis.

The mechanism of cytolysis by murine NK cells was analyzed using a variety of metabolic inhibitors that have proven informative in studying the lytic mechanism of CTL and the mechanism of histamine release by mast cells. Target cell binding occurred in the absence of calcium and was inhibited by only one of the agents studied, cytochalasin B. Lysis was initiated by addition of Ca2+ ions, as in the case of CTL. Subsequent to target cell binding, but prior to programming for lysis by Ca2+, NK cell lytic activity could be suppressed by inhibitors of chymotrypsin-like, but not trypsin-like proteases, in contrast to CTL. In addition, 3-deaza-SIBA, an inhibitor of transmethylation reactions and quinacrine, an inhibitor of phospholipase A2, appear to act before the Ca2+-dependent programming for lysis. Sr2+ ions blocked the lytic function, as did trifluoperazine (stelazine), the former presumably competing for ionic calcium, the latter known to block binding of Ca2+ to calmodulin. 8Br-cAMP and colchicine blocked later steps required for lysis. With the possible exception of trifluoperazine, all of the agents that blocked NK cell lysis are known to inhibit histamine release from mast cells. These results lend support to the stimulus-secretion model, originally proposed to explain the mechanism of CTL cytolysis, as relevant to the mechanism of lysis by NK cells.

Animals↗
PubMed1981

On the heterogeneity of murine natural killer cells.

The heterogeneity of cells capable exerting spontaneous cytotoxicity in vitro was explored using antisera to several genetically determined surface markers on mouse lymphocytes. Four phenotypes of cells derived either from fresh or cultured murine lymphoid tissue were found to exert natural killer (NK) activity in vitro. One affector cell subset, termed NKI cells, had the serological phenotype of Thy-1-, Lyt-2-, Qa5+, and lysed measles virus persistently infected target cells (HeLa-Ms) but not P815 mastocytoma cells. It corresponds with the NK cells described in most systems in which lymphoma targets are commonly used. A second subset, with the same target cell specificity, termed NKT is a thymus-independent cell with the phenotype Thy-1+, Lyt-2-, Qa-5+, Ly-5+. A third subset of NK cells, termed T killer (TK) cells deriving from cultures of conventional but not nude mouse spleens, mediated spontaneous cytotoxicity of P815 mastocytoma cells, but not of virus-infected targets. It has a phenotype of Thy-1+, Lyt-2+, Qa-5-, Ly-5+, apparently identical with that of conventional, antigen-specific cytotoxic T lymphocytes. The fourth phenotype of NK cells, termed NKM, derived primarily from cultures of bone marrow, is cytotoxic for HeLa-measles but not P815, and expresses only Ly-5+ among the various markers tested. Beige mice possess normal TK and NKM activities, but had normal NKI, NKT as well as NKM activity. All NK cell subsets express the Ly-5 surface marker. The existence of four phenotypically distinct NK effector cells was strengthened by studies on selective regulation of their activity by two different biological factors. Interferon (IFN) augmented NK activity of primarily one of the subsets examined, the NKI cell; the activity of IFN on NKT cells could not be directly tested, but IFN was without positive effect on TK or NKM cells. In contrast, partially purified IFN-free interleuken 2 (IL-2) augmented the activities of both the TK and NKT subsets, but not of NKI or NKM cell. IL-2 was active in augmenting NK activity in spleen cells obtained from both conventional and nu/nu mice, but was without effect on spleens of nu/nu mice depleted of Thy-1+ cells. These and other data suggest that IL-2 acts primarily, if not exclusively, on THy-1+ cells. These results strengthen the view that natural cytotoxicity in vitro can be mediated by several distinct cell populations under different genetic and regulatory control and indicate the importance of defining and delineating the cell lineages of each and the role of the independent subsets in resistance to virus infections and tumors in vivo.

Animals↗
PubMed1981

Influence of anti-mouse interferon serum on the growth and metastasis of tumor cells persistently infected with virus and of human prostatic tumors in athymic nude mice.

Baby hamster kidney or HeLa cells form tumors in 100% of athymic nude mice. When such cells are persistently infected (PI) with RNA viruses, such as mumps or measles virus, the tumor cells either fail to grow or form circumscribed benign nodules. Neither the parental nor the virus PI tumor cells form invasive or metastatic lesions in nude mice. Previous studies have indicated a correlation between the susceptibility of virus-PI tumor cells in vitro and the cytolytic activity of natural killer (NK) cells and their failure to grow in vivo. Because interferon (IF) is the principal regulatory molecule governing the differentiation of NK cells, it was possible to test the relevance of the IF-NK cell system in vivo to restriction of tumor growth by treatment of nude mice with anti-IF globulin. This treatment was shown to reduce both IF production and NK activity in spleen cells. Both parental and virus-PI tumor cells grew and formed larger tumors in nude mice treated with anti-IF globulin than in control nude mice. The viral-PI tumor cells and the uninfected parental cells formed tumors in treated mice that were highly invasive and often metastatic. Some human tumor types have been notoriously difficult to establish as tumor lines in nude mice (e.g., primary human prostatic carcinomas). When transplanted into nude mice treated either with anti-IF globulin or anti-lymphocyte serum, two prostatic carcinomas grew and produced neoplasms with local invasiveness and some metastases. The results are consistent with the view that interferon may be important in restricting the growth, invasiveness, and metastases of tumor cells by acting indirectly through components of the immune system, such as NK cells.

Animals↗
PubMed1981

Degradation of the P0, P1, and Pr proteins in peripheral nervous system myelin by plasmin: implications regarding the role of macrophages in demyelinating diseases.

Activated macrophages secrete a variety of neutral proteinases, including plasminogen activator. Since macrophages are implicated in primary demyelination in the peripheral nervous system (PNS) in Guillain-Barré syndrome and experimental allergic neuritis, we have investigated the ability of plasmin and of conditioned media from cultured macrophages, in the presence of plasminogen, to degrade the proteins in bovine and rat PNS myelin. The results indicate that (a) the major glycoprotein P0 and the basic P1 and Pr proteins in PNS myelin are extremely sensitive to plasmin, perhaps more so than is the basic protein in CNS myelin; (b) the initial product of degradation of P0 by plasmin has a molecular weight higher than that of the "X" protein; (c) large degradation products of P0 are relatively insensitive to further degradation; and (d) the neuritogenic P2 protein in PNS myelin is quite resistant to the action of plasmin. Results similar to those with plasmin were obtained with conditioned media from macrophages and macrophage-like cell lines together with plasminogen activator, and the degradation of the PNS myelin proteins, Po and P1, under these conditions was inhibited by p-nitrophenylguanidinobenzoate, an inhibitor of plasmin and plasminogen activator. The results suggest that the macrophage plasminogen activator could participate in inflammatory demyelination in the PNS.

Animals↗
PubMed1981

Interferon responses of leukocytes in multiple sclerosis.

In vitro interferon (IFN) responses of peripheral blood leukocytes to measles virus and to other IFN inducers were determined for multiple sclerosis patients and normal donors. The group mean IFN response to measles virus was significantly lower in patients (15 units) than in normal donors (100 units), and a greater proportion of the patients failed to exhibit a significant IFN response. This defect was not specific for measles virus and was also observed consistently in response to Newcastle disease virus, Poly(I).Poly(C), and concanavalin A. The level of IFN response was not related to the clinical stage of disease.

Adult↗