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Biomedical subjects

B R Bloom

Publications and source records attributed to B R Bloom.

At least 235 records · Page 13Linked to original sources
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↗
PubMed1977

Occurrence of restricted suppressor T-cell activity in man.

Blood leukocytes from an immunologically hyporesponsive patient with urinary bladder carcinoma were found to be deficient in their ability to stimulate 3 of 27 responder leukocyte preparations from normal individuals in one-way mixed leukocyte culture (MLC). The patient's T-depleted leukocytes, however, functioned adequately as stimulator cells. T-enriched lymphocytes from this patient suppressed the MLC responsiveness of those three normals but not the responsiveness of other normals. The patient's cells suppressed the MLC responsiveness of only one of each of the parents of two of the normals who could be suppressed by the patient's leukocytes suggesting a possible genetic restriction to this suppressor cell activity.

HLA Antigens↗
PubMed1977

Differentiation of memory T cells to virus plaque-forming cells and cytotoxic T lymphocytes.

The aims of this study were to define the T-cell subpopulation(s) detected by the virus plaque assay, and particularly to determine whether the virus plaque assay could be used to enumerate cytotoxic T lymphocytes. In addition, studies were undertaken to ascertain whether cell proliferation was required for development of cytotoxic effector function and virus plaque formation by these subpopulations. The results of experiments with a secondary mouse mixed lymphocyte culture (MLC) model indicated that 70 percent of virus plaque-forming cells bore the Ly 1 phenotype and 30 percent the Ly 2,3 phenotype. Three lines of evidence suggested that cytotoxic T lymphocytes (CTL) can be detected by this assay: the fact that some virus plaque-forming cells (V-PFC) bear the same Ly phenotype as CTL; the use of an inhibitor of DNA synthesis indicated that proliferating cells could be eliminated with no effect on V-PFC production and cytotoxic activity of the Ly 2,3 cell population; and that infection of primed lymphocyteswith vesicular stomatitis virus before (MLC) stimulation eliminated cytotoxic activity. In primary MLC, development of V-PFC and CTL was completely abolished by cytosine arabinoside. In contrast, in secondary MLC, some CTL and V- PFC were generated by antigenic stimulation in the absence of proliferation. However, the development of both functions became progressively more susceptible to cytosine arabinoside as the time between primary immunization and in vitro boosting is increased. It is suggested that there may be a considerable disparity between the number of existing effector cells at any given time and the cytotoxic potential, i.e. the number of cells capable of being generated by antigenic stimulation.

Animals↗
PubMed1977

Selective viral immunosuppression of the graft-versus-host reaction.

Graft-vs.-host (GVH) reactivity of parental lymph node (LN) cells was assayed by measurements of 3H-thymidine incorporation in vivo in spleens of irradiated F1 recipients. Preincubation of parental LN cells with vesicular stomatitis virus (VSV) for 2 h at 37 degrees C followed by washing resulted in an 85-90% reduction in splenic radioactivity, as did injection of VSV on days 0-2 after recipients received untreated parental LN cells. In contrast, 3H-thymidine incorporation in the spleens or irradiated F1 hosts was not affected by VSV when F1 bone marrow cells were incubated with the virus. In addition, preincubation of F1 B cells with VSV still allowed these syngeneic B cells to be recruited into proliferation by mitomycin-treated parental LN cells. The inhibitory effect of VSV, thus, seems to be specific for T-cell proliferation. These observations suggest that viral immunosuppression might be capable of being developed into a useful strategy for selective deletion of lymphocytes capable of reacting against histocompatibility antigens and initiating GVH reactions.

Animals↗
PubMed1977

Isolation of variants in phagocytosis of a macrophage-like continuous cell line.

We have isolated cloned variants in phagocytosis from a cloned continuous murine macrophage-like cell line, J 774.2. A selection procedure against Fc receptor-mediated phagocytosis was devised using IgG-coated SRBC containing a toxic drug, tubercidin, as the lethal agent. A series of variant clones deficient in Fc receptor-mediated phagocytosis were isolated. Such variants occurred at low frequency (approximately 6 X 10(-5)), were stable, and appeared to possess Fc receptors. The degree to which they were defective in phagocytosis of IgG-coated SRBC varied from clone to clone, yet all clones, were able to phagocytize latex particles. The phagocytic defect in some variants could be corrected by the addition of 8 Br-cAMP, in others, the drug was without effect. It is likely, therefore, that different variants are defective in several distinct steps critical to Fc receptor-mediated phagocytosis.

Binding Sites↗