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Biomedical subjects

T B Strom

Publications and source records attributed to T B Strom.

At least 217 records · Page 12Linked to original sources
PubMed1987

Genetic assembly and selective toxicity of diphtheria-toxin-related polypeptide hormone fusion proteins.

The reports of Miyanohara et al. (1986) and Murphy et al. (1986) were the first to describe the genetic construction, expression, and receptor-specific selective toxicity of a chimaeric toxin. In the present report, we have extended these earlier observations and have shown that the fusion of a modified gene encoding IL-2 to a truncated diphtheria toxin gene also results in the expression of a biologically active chimaeric IL-2 toxin. In both instances we have used receptor-binding-domain substitution and have genetically coupled those portions of the diphtheria toxin structural gene that encode the ADP-ribosyl transferase activity of fragment A and lipid-associating domains of fragment B to modified genes which encode either the polypeptide hormone alpha-MSH or the T-cell growth factor IL-2. The chimaeric toxins expressed from these gene fusions have been shown to be selectively targeted to those eukaryotic cells that carry specific surface receptors for the ligand compounds of the hybrid. For example, in the case of the IL-2 toxin, it is clear that the selective action of this hybrid protein is based upon both its diphtheria-toxin and IL-2-related components. Following binding to the IL-2R on activated and/or malignant T-cell, IL-2 toxin is internalized by receptor-mediated endocytosis. Upon acidification of the endosome, diphtheria toxin fragment B portions of the chimaeric toxin facilitate the delivery of fragment A to the cytosol where it catalyses the ADP ribosylation of EF-2. The assembly of chimaeric toxins at the level of the gene offers several advantages over chemical linkage. Since chemical linkage of the toxophore and ligand components of the conjugate toxins requires activation of the epsilon-amino moiety of lysine residues with reagents that will allow for subsequent disulphide linkage, the precise site of coupling is generally not known. In addition, there has been considerable concern over the lability of the disulphide bond between the toxophore and ligand components in vivo due to the action of disulphide reductases. The assembly of chimaeric toxins at the level of the gene allows for precise linkage of the toxophore and ligand components. Since the linkage between the toxophore and ligand is a peptide bond, the chimaeric toxin should be stable in vivo. In addition, the genetic construction of chimaeric toxins also allows for further protein engineering through site-directed mutagenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1986

Prostaglandins posttranscriptionally inhibit monocyte expression of interleukin 1 activity by increasing intracellular cyclic adenosine monophosphate.

The effect of prostaglandins and cyclic 3',5'-adenosine monophosphate (cAMP) on expression of human interleukin 1 (IL 1) activity was investigated in the promonocytic tumor cell line U937 and peripheral blood monocytes. After in vitro stimulation by bacteriotoxins, monocytes express IL 1 activity, as measured by the thymocyte costimulation assay. Although high doses of bacteriotoxins impaired expression of IL 1, this effect was reversed by indomethacin. When stimulated monocytes were cultured with exogenous prostaglandins, including PGE2 and PGI2, expression of IL 1 was reversibly inhibited. Interaction of U937 cells with PGE2 resulted in a transient increase in cellular cAMP concentration during the first hour of exposure. Other agents that cause an increase in levels of cellular cAMP, including theophylline, isobutylmethylxanthine, dibutyryl cAMP, or cholera toxin, also reversibly reduced expression of IL 1 by stimulated monocytes. The effect of these agents on levels of IL 1 mRNA was analyzed. TSS-stimulated increase in levels of IL 1-encoding mRNA was studied both by DNA-RNA hybridization analysis performed with an IL 1-beta cDNA probe and by injecting U937 polyadenylated mRNA into frog oocytes and then measuring expression of IL 1 activity in the oocyte supernatant. Agents that increased levels of cellular cAMP did not alter levels of IL 1 mRNA accumulation or global protein synthesis in TSS-stimulated U937 cells. IL 1 stimulates synthesis of prostaglandins that reach high levels during immune and inflammatory reactions. Our data suggest that prostaglandins participate in an autoregulatory pathway that posttranscriptionally reduces expression of IL 1 activity.

Cell Line↗
PubMed1986

Anti-interleukin 2 receptor antibody suppresses delayed-type hypersensitivity to foreign and syngeneic antigens.

Delayed-type hypersensitivity (DTH) requires stimulation of antigen-specific helper T cells (Th). Because de novo expression of the interleukin 2 receptor (IL 2R) is a necessary step in T cell activation, we tested the capacity of anti-mouse IL 2R monoclonal antibody (Mab) and anti-Th Mab (anti-L3T4) to block DTH. We examined the effect of these Mab on two distinct DTH systems, i.e., to foreign hapten (trinitrobenzenesulfonic acid) and to this hapten present on syngeneic blasts. Both anti-IL 2R and anti-L3T4 Mab suppress DTH. Therapy is as effective treating with one injection just before challenge with the hapten as giving six daily injections. These data indicate that DTH is dependent on a discrete subset of activated IL 2R-positive T cells, because anti-IL 2R therapy, which targets few cells, is as effective as anti-L3T4 Mab treatment, which targets the entire Th subset.

Animals↗
PubMed1986

Purification and characterization of a unique human interleukin 1 from the tumor cell line U937.

Interleukin 1 (IL 1) produced by a human tumor cell line was purified to homogeneity by a three-step chromatographic method and was tested in various assays for multiple biologic properties. The purified IL 1 stimulated the proliferative response of the D10.G4.1 cell line, a mouse IL 1 indicator T cell; caused the release of prostaglandin E2 and prostacyclin from cultured human foreskin fibroblasts and from primary human umbilical vein endothelial cells; and elicited characteristic endogenous pyrogen fever in rabbits. To stimulate IL 1 production, the histiocytic lymphoma cell line U937 was incubated with the exotoxin from toxic shock strains of Staphylococcus aureus. Supernatants from stimulated U937 cells were concentrated, and were applied to a reverse-phase HPLC column. IL 1 activity was eluted from the column at high acetonitrile concentration. Subsequent chromatography over hydroxyapatite yielded a single IL 1 species with a pI of 5.5. IL 1 was then purified to homogeneity by gel exclusion HPLC migrating as a 14 kDa species. The molecular size was confirmed by SDS-PAGE and was visualized as a single molecule by silver staining; biologic activity was recovered from the same region of the gel. Limited N-terminal sequence analysis suggested some homology to the pI 7 form of the human blood monocyte IL 1. The pI 5.5 IL 1 produced by U937 cells was only partially neutralized with anti-human monocyte IL 1 antibody, suggesting that U937-derived IL 1 is structurally related to one of the molecularly cloned IL 1 species. IL 1 from stimulated U937 cells possesses the functional characteristics of monocyte IL 1 but may represent a structurally unique IL 1 species, as determined by sequence analysis, size, and antibody reactivity.

Amino Acid Sequence↗
PubMed1986

Stages of T cell activation: continued antigen dependence of IL 2-producing cells after IL 2 receptor expression.

Alloantigen stimulation leads, within 48 to 72 hr, to the expression of IL 2 receptors (IL 2R) on the surface of most of the helper T cells with specificity for the stimulating antigens. The IL 2R-bearing cells, separated by flow cytometry from 3-day human or mouse mixed lymphocyte cultures, were found by limiting dilution methods to be enriched 10- to 20-fold (compared to IL 2R- cells) for antigen-specific helper T cells detected by IL 2 production. Although these cells have been activated to an IL 2R+ stage, most of them are unable to produce detectable IL 2 unless they are cultured together with the original, activating antigen. Even when IL 2 is supplied, and lymphokine production measured by assay of a second factor, IL 3, the large majority of individual activated helper T cells remain dependent on further antigenic exposure for their continued maturation into lymphokine-secreting effectors. Helper T cells at this early stage of activation can therefore proliferate when given IL 2 alone, but lymphokine secretion involves a second antigen-dependent step.

Animals↗
PubMed1986

Inability of autoimmune mice with the lpr gene to spontaneously produce interleukin 3.

A recent report (Palacios, R., Eur. J. Immunol. 1984. 14: 599) indicates that spleen cells from MRL-MpJ-lpr/lpr mice spontaneously produce interleukin 3 (IL 3) and suggests that this lymphokine could be responsible for promoting the lymphoid hyperplasia regulated by the lpr gene. The present study shows that splenocytes from several murine strains bearing the lpr gene do not spontaneously produce IL3. This has been determined by measuring the amount of this lymphokine by a bioassay and by the detection of IL3 mRNA using Northern blot analysis. We suggest that another lymphokine is responsible for growth of lymphocytes regulated by the lpr gene.

Animals↗
PubMed1986

Immunological response to stress in agoraphobia and panic attacks.

The authors studied in vitro immune function as measured by lymphocytic proliferative response to mitogen stimulation in 36 patients with agoraphobia and panic attacks who were participating in a double-blind placebo-controlled psychopharmacological study of anxiety disorder. No significant difference in immune status was observed between panic patients and healthy controls.

Adult↗
PubMed1986

Spleen cell factor inhibits lymphoproliferation, abnormal Ia expression and overt autoimmunity in MRL-lpr mice.

Autoimmune MRL-lpr have an abnormal pattern of lymphokine production. In our attempt to repair this defect, MRL-lpr mice were prophylactically treated daily with a lectin stimulated rat spleen cell product rich in interleukin-2. Therapy inhibited the lymphoid hyperplasia of the unique lymphocytes regulated by the lpr gene, suppressed the enhanced supranormal expression of Ia on peritoneal macrophages and protected this strain from autoimmune renal injury. Purified recombinant interleukin-2 alone did not prevent autoimmune disease expression. Thus, a spleen cell product other than interleukin-2 can ameliorate the aggressive course of lymphoproliferation and autoimmunity in MRL-lpr mice.

Animals↗
PubMed1986

Natural killer cell response to interferons.

The availability of recombinant interferons has facilitated a comparison of the in vitro effects of interferon-alpha and -gamma upon human natural killer (NK) cells. In the absence of interferon high and low NK responders exist. Repeated testing of the same individuals revealed different but stable NK patterns to in vitro addition of interferon-alpha and -gamma Furthermore, the NK cell response patterns differed depending on whether the interferons were administered in combination or separately. These studies suggest new complexities that must be addressed in the planning and execution of clinical interferon trials. The pattern of responsiveness of human NK cells to interferon-alpha or -gamma or both is highly variable, but stable, within a given individual.

Cytotoxicity, Immunologic↗