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Biomedical subjects

B R Bloom

Publications and source records attributed to B R Bloom.

At least 289 records · Page 16Linked to original sources
PubMed1971

On the number and nature of antigen-sensitive lymphocytes in the blood of delayed-hypersensitive human donors.

The virus plaque assay has been successfully employed to enumerate antigen-sensitive cells in the peripheral blood lymphocyte populations of tuberculin-hypersensitive human donors. The method is based on the finding that, while resting lymphocytes are unable to produce a variety of viruses upon infection, lymphocytes activated by specific antigens become capable of virus replication. The average number of antigen-sensitive cells detected in cell populations from donors reacting to first test strength or intermediate test strength tuberculin was approximately 3.6/1000 lymphocytes, and the averages for both groups were similar. Studies on the kinetics of appearance of these virus plaque-forming cells and on the effects of the mitotic inhibitor, vinblastine, indicate that the activation of these antigen-sensitive cells is a linear process and that the cells must be nondividing cells during this process. These qualities contrast markedly with those described for the mitogenic response and the antibody-producing cells which require cell division and increase exponentially. On the basis of these experiments it is suggested that the antigen-sensitive cell measured in the virus plaque assay is the effector cell in delayed-type hypersensitivity reactions and, in addition, may be one of the cells critically involved in antibody formation.

Antibody-Producing Cells↗
PubMed1970

A plaque assay for enumerating antigen-sensitive cells in delayed-type hypersensitivity.

A general method is described for enumerating antigen-sensitive lymphocytes obtained from individuals having delayed hypersensitivity, in this case from highly tuberculin-sensitive guinea pigs. The method is based on the observation that resting lymphocytes are generally unable to support replication of RNA viruses, whereas antigen-"activated" lymphocytes can. Lymph node lymphocytes from individual animals were cultured in the presence or absence of tuberculin purified protein derivatives (PPD). After various periods of time, the cells were infected either with Newcastle disease virus or vesicular stomatitis virus, and plated in agar over a monolayer of cells susceptible to the virus. Wherever a lymphocyte yielded infectious virus, a discrete plaque in the monolayer could be seen. The increase in plaques of the antigen-stimulated cells over the background of the control sample was taken as the number of antigen-sensitive cells in the population. When lymphocytes from normal guinea pigs or from guinea pigs immunized to produce only circulating antibody to PPD were similarly tested, no increase in plaque-forming units (PFU) was observed. The average increase in PFU due to antigenic stimulation varied from 1 per 1000 lymphocytes at 24 hr to 16 per 1000 lymphocytes at 96 hr. By employing inhibitors of mitosis (colchicine, vinblastine, and thymidine) it was evident that the increase in PFU at least up to 48 hr was primarily due to initial antigen-reactive cells and not their progeny.

Animals↗
PubMed1969

Demonstration of delayed hypersensitivity to soluble antigens of chemically induced tumors by inhibition of macrophage migration.

Sensitization to soluble antigens of chemically induced tumors is demonstrable in syngeneic strain 13 (inbred) guinea pigs by specific inhibition of macrophage migration. According to their capacity to (a) inhibit the migration of peritoneal cells from sensitized strain 13 donors or (b) release migration-inhibitory factor from their lymph node cells, the soluble antigens of three different chemically induced tumors did not cross react. This is in keeping with the absence of cross-reactivity among the same three tumors in previous tests of transplantation resistance or delayed hypersensitivity in vivo. Thus, inhibition of macrophage migration may provide a feasible assay in vitro for use in defining these soluble antigens further by physicochemical methods.

Animals↗
PubMed1966

Mechanism of a reaction in vitro associated with delayed-type hypersensitivity.

The cell type responsible for inhibition by antigen of migration in vitro of peritoneal exudate cells obtained from tuberculin-hypersensitive guinea pigs was studied. Exudate populations were separated into component cell types, the lymphocyte and the macrophage. Peritoneal lymphocytes from sensitive donors were the immunologically active cells in this system, the macrophages, being merely indicator cells which migrate. Sensitized peritoneal lymphocyte populations, upon interaction with specific antigen in vitro, elaborated into the medium a soluble material capable of inhibiting migration of normal exudate cells.

Animals↗
PubMedDate not supplied

Genes for the protein antigens of the tuberculosis and leprosy bacilli.

The lambda gt 11 expression vector permitted us to survey protein antigens of Mycobacterium leprae and Mycobacterium tuberculosis expressed in Escherichia coli. Using monoclonal antibodies, recombinant clones were detected producing three major antigens of M. tuberculosis and five major protein antigens of M. leprae. These recombinant antigens produced in E. coli should prove useful for diagnosis, epidemiology and possibly the development of recombinant mycobacterial vaccines.

Antigens, Viral↗
PubMedDate not supplied

Recombinant BCG as a candidate oral vaccine vector.

Bacille Calmette-Guerin (BCG), currently the most widely used vaccine in the world, was originally administered for many years as an oral vaccine. The low frequency of serious complications, inexpensive production, and adjuvanticity make BCG an ideal candidate for a recombinant vaccine vehicle. Although mycobacteria are slow growing and not yet well characterized genetically, we have recently developed technology for the genetic manipulation of BCG and other mycobacteria. Phage and plasmid systems based on a shuttle strategy to manipulate DNA in Escherichia coli and transfer it to mycobacteria have been developed. We have established that the aminoglycoside phosphotransferase gene can be used as an effective selectable marker in the mycobacteria and that a foreign antigen from Mycobacterium leprae can be expressed in BCG. Furthermore, a thorough analysis of mycobacterial expression sequences has been undertaken to optimize the expression of foreign antigens in BCG. We constructed an expression probe shuttle plasmid with beta-galactosidase as reporter gene, and have used it successfully to identify multiple mycobacteriophage DNA sequences with varying levels of constitutive or regulable promoter activity. Further genetic advances required for development of recombinant BCG into an effective recombinant vaccine vehicle, including possibilities for oral administration, are adumbrated.

Administration, Oral↗
PubMedDate not supplied

The generation of human monocyte/macrophage cell lines.

The development of continuous murine macrophage-like cell lines has permitted direct and somatic cell genetic approaches to a variety of functions of murine mononuclear phagocytes. However, few, if any, human cell lines exist that have the general characteristics of macrophages, although a promonocyte line, U937, has been reported which can be induced to differentiate into non-dividing cells with macrophage-like properties. Although murine macrophage-like lines have been obtained by transformation with simian virus 40 (SV40), this technique has not, in general, been useful in producing human cell lines, presumably because SV40 causes a lytic infection in human cells. We have therefore developed a method for transfecting primary human monocytes with SV40 DNA deleted in the origin of replication. Using this method, we have now, we believe for the first time, generated transformed human cell lines with macrophage characteristics. Three cell lines from three transfections of human monocytes expressed macrophage enzymes, phagocytic function, surface receptors including HLA-DR and DS and alloantigen presenting activity.

Cell Line↗
PubMedDate not supplied

Lymphocyte suppression in leprosy induced by unique M. leprae glycolipid.

Leprosy remains a significant medical and social problem in many developing countries. The varied forms of the disease form a spectrum. At one pole, tuberculoid leprosy, patients develop high levels of cell-mediated immunity which results in the killing and clearing of bacilli in the tissues. At the lepromatous pole, patients exhibit a selective immunological unresponsiveness to antigens of Mycobacterium leprae so that the organisms inexorably multiply in the skin. We have suggested that in lepromatous leprosy one or a small number of unique antigenic determinants present on M. leprae might induce specific suppressor cells that inhibit the reactivity of helper T-cell clones capable of recognizing other specific or cross reactive determinants. Although unique epitopes have been identified by monoclonal antibodies on a small number of M. leprae proteins, the only unique species of antigen present in M. leprae, and not on any other species of mycobacteria so far examined, is a phenolic glycolipid (gly-I). We show here that this unique antigen of M. leprae is capable of inducing suppression of mitogenic responses of lepromatous patients' lymphocytes in vitro and provide evidence that the suppressor T cells recognize the specific terminal trisaccharide moiety.

Antigens, Bacterial↗