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Biomedical subjects

B R Bloom

Publications and source records attributed to B R Bloom.

At least 19 recordsLinked to original sources
PubMed1979

Mechanism of rejection of virus persistently infected tumor cells by athymic nude mice.

Cell lines known to be tumorigenic in the nude mouse were modified by rendering them persistently infected (P.I.) with a variety of RNA viruses, including measles, mumps, vesicular stomatitis virus, and influenza. Although as few as 100 HeLa or BHK cells produced tumors in 100% of nude mice, as many as 2 x 10(7) of the same cells P.I. with viruses failed to produce tumors. An active host response responsible for restricting the growth of the P.I. cells was suggested by the findings of marked mononuclear cell infiltrates at the inoculation sites and the inability of irradiated nude mice to reject them. An analysis of the in vitro cytotoxic activity of spleen cells from normal nude mice indicated that: (a) P.I. cell lines, but not uninfected cell lines, were susceptible to spontaneous cytotoxicity; (b) in vivo inoculation of P.I. lines induced an enhanced cytotoxic activity for P.I. targets in vitro, and this induction was not specific either for inducing virus or cell line; and (c) the effector cell had the characteristics for natural killer (NK) cells. Although the specificity of recognition of the various P.I. cell lines remains unclear, cold competition experiments indicated that blocking the killing of one P.I. cell line, e.g. HeLa-measles, could be achieved only by unlabeled homologous cells, i.e. HeLa-measles, and not by uninfected cells or other P.I. lines. A variant subline of BHK cells P.I. with VSV was selected for its ability to withstand the rejection process in nude mice. These cells formed metastatic and invasive tumors in nude mice. Although they were the most potent inducers in vivo of NK cell activity against various P.I. targets, they were the most resistant of the P.I. lines to NK cell cytotoxicity in vitro. In this system there was a good correlation between tumor rejection in vivo and susceptibility to NK cells in vitro. The present results suggest that NK cells may play a significant role in both rejection of tumor cells, and in resistance to viruses, particularly persistent infections.

Animals↗
PubMed1979

Properties of protein kinase and adenylate cyclase-deficient variants of a macrophage-like cell line.

Stable variants of the macrophage-like cell line J774.2, defective in adenylate cyclase and protein kinase activities, were selected by cloning cells resistant to the growth-inhibitory effect of cholera toxin and 8-bromo-adenosine 3':5' cyclic monophosphoric acid (8 Br-cAMP), respectively. These variants were analyzed for their ability to respond to cyclic AMP-mediated enhancement of phagocytosis and cyclic AMP-mediated inhibition of plasminogen activator secretion and growtn. The adenylate cyclase variants were unaffected by cholera toxin but were sensitive to 8 Br-cAMP-mediated inhibition of plasminogen activator secretion and growth. One of these variants exhibited a defect in phagocytosis that could be corrected by 8 Br-cAMP. The protein kinase variants exhibited normal basal phagocytosis that could not be stimulated by either 8 Br-cAMP or cholera toxin; they were also insensitive to cyclic AMP-mediated inhibition of plasminogen activator secretion and growth. The studies demonstrate that the three effects of cyclic AMP in J774.2--inhibition of growth and plasminogen activator secretion, and enhancement of basal Fc-mediated phagocytosis--are mediated by a cyclic AMP-dependent portein kinase. The results support the usefulness of variants in cyclic nucleotide metabolism in understanding the regulation of differentiated cell function by cyclic AMP.

Adenylyl Cyclases↗
PubMed1979

Absence of virus-induced lymphocyte suppression and interferon production in multiple sclerosis.

Lymphocytes from normal adult donors exposed in vitro to inactivated measles virus were found to exert significant suppression (33.9%) of the concanavalin A responses of cryopreserved, autochthonous responder cells. In marked contrast, lymphocytes from multiple sclerosis patients exhibited significantly reduced suppression (1.5%), and in 80% of cases failed to suppress at all. The degree of suppression increased slightly with age of the patient but did not vary with the clinical stage of disease. There was no apparent genetic restriction of suppressor activity. Although specificity of this phenomenon for measles virus has not been established, no differences in the responses of lymphocytes from normal or multiple sclerosis patient donors were found with subacute sclerosing panencephalitis, Sendai, canine distemper, mumps, or influenza viruses. Supernates of measles-treated lymphocytes from normal donors possessed both suppressive and antiviral activities. Both activities were resistant to pH 2 treatment and were neutralized by an anti-human leukocyte interferon antiserum, strongly suggesting that interferon (probably type I) was the mediator of suppression. Consistent with their inability to suppress concanavalin A responses, lymphocytes from multiple sclerosis patients failed to produce significant amounts of interferon in response to measles challenge in vitro. These results extend previous observations that multiple sclerosis patients are unable to respond appropriately to measles virus antigen in vitro.

Adult↗
PubMed1979

Induction of cell-mediated immunity to Mycobacterium leprae in guinea pigs.

Guinea pigs immunized with intact or disrupted armadillo-grown human Mycobacterium leprae administered in aqueous or oil vehicles were tested with various dilutions of M. leprae suspended in saline, water-soluble M. leprae extract, purified protein derivative, and a water-soluble extract of normal armadillo tissue. The results demonstrated the following. (i) Under no conditions was any skin test reactivity found to normal armadillo tissue extract. (ii) Positive sensitization to both M. leprae and its water-soluble extract was achieved by sensitizing guinea pigs with M. leprae suspended in Hanks solution or saline. Autoclaved M. leprae in Hanks solution or saline inoculated intradermally was an effective immunogen. Oil suspensions or emulsions were effective at sensitization, but appeared to be no better and, in general, slightly weaker, than simple inoculation in aqueous suspension. (iii) Living BCG failed to reveal a significant adjuvant effect on sensitization to M. leprae. However, cord factor appeared to potentiate slightly the sensitization to M. leprae in aqueous suspension. (iv) The minimum dose required for sensitization with M. leprae in aqueous suspension was 55 micrograms of purified bacilli. (v) Animals inoculated with M. leprae in saline or with M. leprae together with BCG showed positive skin test reactivity to the first skin test application made fully 1 year after the initial sensitization. The efficacy of autoclaved, irradiated M. leprae in aqueous, oil-free medium suggests a relatively safe approach to human vaccination studies.

Adjuvants, Immunologic↗
PubMed1979

Lepromin-induced suppressor cells in patients with leprosy.

The possibility of an active mechanism of immunologic suppression in leprosy was explored by assessing the in vitro lymphocyte responses of 61 leprosy patients and 30 normal individuals to the mitogen Con A in the presence or absence of Dharmendra lepromin. Lepromin-induced suppression of Con A stimulation was found in 32 of 35 lepromatous patients and 15 of 15 borderline patients, but only 2 of 15 tuberculoid patients and 2 of 30 normal controls. Cell fractionation studies indicated at least two cell populations involved in the in vitro lepromin-induced suppressor activity, adherent cells and T gamma-cells.

Cell Adhesion↗
PubMed1978

Isolation of a heterogeneous population of temperature-sensitive mutants of measles virus from persistently infected human lymphoblastoid cell lines.

Two human lymphoblastoid B-cell lines, WI-L2 and 8866, were infected with the Edmonston strain of measles virus at a multiplicity of infection of 10(-6), and stable persistent infections were established. By immunofluorescence and electron microscopy, the vast majority of cells from both cell lines were expressing viral antigens and releasing virion-like particles. However, very little infectious virus could be detected at 37 degrees C, either by an infectious centers assay or by titration of supernates from persistently infected cultures. When cultures were shifted to 31 degrees C, the cells released a population of virus that was temperature-sensitive. Clonal analysis of supernatant virus at 31 degrees C revealed a highly heterogeneous population of temperature-sensitive mutants, differing in plating efficiency ratios, thermolability, and antigen production at the nonpermissive temperature. Factors such as interferon, defective interfering particles, and extracellular virus do not appear to be important in maintaining the persistent carrier state. These studies have important implications for persistent infections of lymphoid cells in vivo, and the slow neurological diseases associated with measles, subacute sclerosing panencephalitis, and multiple sclerosis.

Antibodies, Viral↗
PubMed1978

Neutral proteinases secreted by macrophages degrade basic protein: a possible mechanism of inflammatory demyelination.

In the inflammatory demyelinating diseases, such as multiple sclerosis, Landry-Guillain-Barré syndrome and experimental allergic encephalomyelitis, demyelination occurs in the vicinity of infiltrating mononuclear cells. Although the histopathology is characteristic of each disease, the general observation that myelin destruction in inflammatory lesions begins prior to phagocytosis suggests a common mechanism for myelinolysis in these diseases. Recent studies show that stimulated macrophages secrete several neutral proteinases, including plasminogen (Plg) activator. We have tested the possibility that these proteinases could, directly or indirectly, initiate myelin destruction. Isolated brain myelin was incubated with supernatant media from cultures of stimulated mouse peritoneal macrophages in the presence and absence of Plg. Cell supernatants alone caused some degradation of basic protein (BP) in myelin. The amount degraded was considerably enhanced in the presence of Plg. The other myelin proteins remained essentially intact. While the Plg-independent proteolytic activity in the supernatants was abolished by EDTA, known to inhibit the neutral proteinases, the Plg-dependent hydrolysis was inhibited by p-nitrophenylguanidinobenzoate, an inhibitor of Plg activator and plasmin. These results suggested that the Plg activator secreted by the macrophages generated plasmin, which selectively degraded BP. This interpretation was confirmed by the observation that urokinase, a Plg activator, plus Plg was effective in degrading BP in myelin. We propose that the action of neutral proteinases released by stimulated macrophages, and its amplification by the Plg-plasmin system, may play a significant role in several inflammatory demyelinating diseases; and that the relative specificity of these reactions for myelin lies in the extreme susceptibility of BP to proteolysis.

Animals↗
PubMed1978

Degradation of basic protein in myelin by neutral proteases secreted by stimulated macrophages: a possible mechanism of inflammatory demyelination.

In inflammatory demyelinating diseases such as multiple sclerosis and experimental allergic encephalomyelitis, myelin destruction occurs in the vicinity of infiltrating mononuclear cells. The observations that myelin can be altered prior to phagocytosis and in areas not contiguous with inflammatory cells suggests a common mechanism for the initial stages of demyelination. Because stimulated macrophages secrete several neutral proteases, including plasminogen activator, we have investigated the possibility that myelinolysis could be mediated directly or indirectly by these enzymes. Isolated myelin was incubated with conditioned media from cultures of thioglycollate-stimulated mouse peritoneal macrophages in the presence and absence of plasminogen. Myelin appeared to be vulnerable to attack by at least two proteolytic activities secreted by the macrophages, a plasminogen-dependent and a plasminogen-independent activity; of the major proteins in myelin, the basic protein was most susceptible. The direct myelinolytic activity of macrophage-conditioned media was abolished by EDTA, and the plasminogen-dependent hydrolysis was abolished by p-nitrophenylguanidinobenzoate, an inhibitor of plasminogen activator and plasmin. These results suggest that the plasminogen activator released by the stimulated macrophages generated plasmin which hydrolyzed basic protein in intact myelin. This interpretation was confirmed by the observation that urokinase, a plasminogen activator, in the presence of plasminogen brought about marked degradation of basic protein in myelin. We propose that the release of neutral proteases by stimulated macrophages involved in cell-mediated reactions, and its amplification by the plasminogen-plasmin system, may play a significant role in the demyelination observed in several inflammatory demyelinating diseases.

Animals↗
PubMed1978

Susceptibility of mice to acute and persistent measles infection.

Intracerebral inoculation of neonatal mice with the Edmonston strain of measles virus produced an acute, lethal encephalitis and thymic dysplasia in susceptible mice. There was an age-related development of resistance to infection. This resistance was strain-dependent and appeared to be associated with the extent of virus growth in the brain. Studies on the genetic basis for susceptibility, using hybrid and backcross mice, revealed that the principal determinant of host resistance to acute infection was a dominant gene or genes which segregated independently of the H-2 complex. A small number of survivors of the acute infection showed persistence of measles virus antigens in the cerebellum and spleen for up to 2 months after inoculation. However, the low frequency of this persistence indicated that, at this time, intracerebral inoculation of neonatal mice with the Edmonston strain of measles virus constitutes a difficult model for the study of persistant measles infection.

Acute Disease↗
PubMed1978

Inhibition of plasminogen activator secretion by cyclic AMP in a macrophage-like cell line.

The continuous cell line, J774.2, exhibits many macrophage-like functions such as latex and Fc-mediated phagocytosis, antibody mediated phagocytosis, antibody mediated cytotoxicity, chemotaxis, and lysozyme secretion. Cyclic AMP stimulates Fc-mediated phagocytosis and inhibits the growth of J774.2. To further evaluate the relationship between cyclic AMP and the specialized functions exhibited by these cells. Variants deficient in phagocytosis, adenylate cyclase and cyclic AMP-dependent protein kinase were derived. We have now shown that J774.2 also secretes plasminogen activator and that this secretion is rapidly and specifically inhibited by 8-bromoadenosine 3':5'-cyclic monophosphoric acid (8 Br--cAMP) or cholera toxin under conditions where lysozyme secretion is unaltered. Utilizing protein kinase-deficient variants, the ability of cyclic AMP to inhibit plasminogen activator secretion was shown to be mediated by a cyclic AMP-dependent protein kinase. We conclude that cyclic AMP has diametrically opposing effects on two macrophage-like functions: Fc-mediated phagocytosis and plasminogen activator secretion.

Animals↗