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T B Strom

Publications and source records attributed to T B Strom.

At least 109 records · Page 6Linked to original sources
PubMed1994

Quantitative comparison of rapamycin and cyclosporine effects on cytokine gene expression studied by reverse transcriptase-competitive polymerase chain reaction.

We developed and applied a quantitative competitive polymerase chain reaction method to study the expression of various cytokine genes in Con A-stimulated murine splenocytes. This method relies on the use of competitive templates that differ from the target cytokine cDNA templates only by the introduction of a unique restriction endonuclease site in the center of each competitive template. After same-tube amplification using a single pair of oligonucleotide primers for both the target and competitive templates, restriction with the unique endonuclease yields 2 species that are readily resolved on agarose gel electrophoresis: full-length target and half-length competitor fragments. Using this method, we studied the time course and effects of CsA and rapamycin on IL-2, IFN-gamma, IL-4, and IL-10 gene expression following Con A stimulation. IL-2, IFN-gamma, and IL-10 share a common pattern of gene expression peaking at approximately 6 hr, while IL-4 gene expression peaks later, at approximately 20 hr. CsA very effectively inhibits expression of IL-2, IFN-gamma, and IL-4, but it inhibits IL-10 expression only 65%. Rapamycin inhibits IL-10 gene expression 100% and is less effective inhibiting the other cytokines. This pattern of inhibition is consistent with a calcium and protein kinase C independent pathway for IL-10 gene regulation and supports the notion that CsA and rapamycin may be used together to advantage.

Animals↗
PubMed1994

Heightened intragraft CTL gene expression in acutely rejecting renal allografts.

The role of CTL in the immunopathogenesis of acute cellular rejection is controversial. To further define the relationship of activated CTLs to rejection, we analyzed gene expression of three CTL-derived effector molecules in renal allograft biopsies. CTLs are endowed with the ability to promote allograft damage through the elaboration of these highly cytopathic molecules. Intragraft gene transcript levels were determined for granzyme B, perforin, and TIA-1 and correlated with the immunologic status of the allograft as categorized by conventional clinical and histologic criteria. The categories were acute cellular rejection, chronic rejection, elements of both acute and chronic rejection, and no evidence of rejection. Biopsies were snap-frozen, total RNA extracted, and the mRNA converted to cDNA by reverse transcription. Levels were quantitated by competitive template PCR techniques. Intragraft granzyme B and perforin transcripts were highly restricted to biopsies in the acute cellular rejection category. TIA-1 expression was more ubiquitous but significantly higher transcript levels were found in the acute rejection category. The presence of these transcripts in acute cellular rejection samples implicates CTL in the pathogenesis. Moreover, intragraft CTL-specific transcript levels may serve as markers of rejection.

Base Sequence↗
PubMed1994

The immunosuppressive effects of verapamil upon mitogen activated and allo-antigen inducible human cytotoxic T-lymphocytes.

In this study, the effect of verapamil, a phenylalkylamine-type Ca2+ antagonist, upon the activation of human mononuclear cells was investigated and a detailed analysis of the kinetics and dose related effects of verapamil upon alloreactive cytotoxic T-cells (CTL) was undertaken. Verapamil suppressed the release of interleukin-2, proliferation and generation of CTL activity in mitogen and alloantigen stimulated human T-lymphocytes in a dose related fashion. Verapamil suppressed the steady state levels of several T-cell activation-associated gene transcripts, i.e. the mRNA encoding for interleukin-2, and a cytotoxic T-cell specific serine esterase. Verapamil exerted a novel immune-suppressive effect, i.e. the inhibition of mature alloantigen-inducible cytolytic T-cells, thus rendering verapamil a progenitor of potent and clinically useful immunosuppressive drugs.

Cytotoxicity Tests, Immunologic↗
PubMed1994

Cytokines and the Th1/Th2 paradigm in transplantation.

With studies elucidating the cytokine programs associated with T-cell activation, allograft rejection and tolerance induction, the Th1/Th2 paradigm has become a unifying model to explain the observed cytokine profiles. The proof that these cytokines mediate allograft tolerance, however, is at best indirect. More recent studies highlighting the redundant and pleiotropic nature of cytokine networks suggest that the Th1/Th2 paradigm may not be sufficient to explain fully the mechanisms underlying allograft tolerance.

Animals↗
PubMed1994

B7(+)-transfectant tubular epithelial cells induce T cell anergy, ignorance or proliferation.

We have previously established that interferon (IFN)-gamma stimulated, antigen-pulsed tubular epithelial cells (TEC) stimulate antigen (Ag) specific activation of T cell hybridomas to express IL-2. In contrast, these Ag pulsed TEC do not stimulate T helper 1 (Th1) clones to proliferate, but rather render them unresponsive, since Ag pulsed spleen cells cannot restore these cells to proliferate. The interaction of the T cell CD28 surface protein with its ligand B7 expressed on Ag presenting cells bearing Ia is a potent co-stimulatory signal capable of inducing T cell proliferation. Hence, the lack of B7 on TEC was hypothesized to be responsible for anergy in these Th1 cells. Therefore, the B7 gene was transfected into a SV40 transformed TEC or Chinese hamster ovary (CHO) cells, and created TEC and CHO cells expressing surface B7 protein. TEC-B7 (IFN-gamma stimulated, Ag pulsed) express Ia and induce IL-2 production by T cell hybridomas. In contrast, T cell proliferation was not induced by TEC-B7 or CHO-B7 cells; however, these Th1 cells were not anergic since they could be stimulated to proliferate to Ag pulsed spleen cells (immunological ignorance). However, co-cultivating TEC- B7 (IFN-gamma stimulated, Ag pulsed) with Th1 cells stimulated through the T cell receptor (TCR) using anti-CD3 monoclonal antibody (mAb) caused these Th1 cells to proliferate. Furthermore, anti-CD28 and anti-B7 mAbs blocked this response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Rapamycin treatment depresses intragraft expression of KC/MIP-2, granzyme B, and IFN-gamma in rat recipients of cardiac allografts.

Rapamycin (RPM) treatment prevents accelerated rejection of cardiac allografts in sensitized rats. The prominent feature of this brisk 24-h rejection, which includes a panoply of both cellular and humoral host immune responses, is a massive infiltration of rejecting grafts with neutrophils. In this study we tested the hypothesis that RPM-mediated therapeutic effects on accelerated rejection may be linked to decreased expression of protein encoded by gro/melanoma-growth stimulatory activity gene (KC) and macrophage inflammatory protein-2 (MIP-2) genes, the operational rat homologues of the human intercrine-alpha cytokines with proinflammatory IL-8-like neutrophil activation/chemotactic properties. The induction of these genes was then correlated with mRNA profiles encoding for Th1-selective IFN-gamma and CTL-specific granzyme B proteins. Northern blot analysis of RNA from cardiac allografts of sensitized untreated recipients, revealed maximal levels of KC and MIP-2 mRNA at 3 to 6 h after transplantation. In contrast, IFN-gamma mRNA, which was at most very weakly expressed at 3 h, peaked between 6 to 12 h. As with IFN-gamma, granzyme B transcripts were undetectable at 3 h, but peaked around the time of actual graft rejection at 24 h. RPM therapy abrogated accelerated rejection and prolonged cardiac allograft survival to ca. 46 days. This effect was associated with markedly reduced expression of KC and MIP-2 mRNA in the first 24 h as well as at 7 and 34 days after transplantation. Moreover, RPM completely blocked intragraft appearance of granzyme B and IFN-gamma mRNA in long term cardiac allografts. Immunohistologic analysis has revealed that accelerated rejection was associated with extensive neutrophil infiltration, which peaked at 18 to 24 h. At this time, leukocytes and endothelium were intensely stained for IL-8 and IFN-gamma antibodies. In contrast, the allografts from RPM-treated hosts showed essentially no neutrophil infiltration and minor, focal staining for IL-8 and IFN-gamma. This study demonstrates an association between the early expression of genes for proinflammatory IL-8-dependent neutrophil chemotactic activity, and later expression of genes associated with activation/effector activity of CTL and NK cells. It also documents a novel effect of RPM in vivo, which results in the suppression of intragraft IL-8-like and CTL-dependent mRNA/protein production and diminished neutrophil infiltration; these may contribute to the striking efficacy of RPM therapy in sensitized graft recipients.

Animals↗
PubMed1993

Unmodified pancreatic islet allograft rejection results in the preferential expression of certain T cell activation transcripts.

Polymerase chain reaction-assisted reverse transcription was used to study the temporal course of rejection in unmodified recipients of murine pancreatic islet cell allografts (DBA/2-->B6AF1) by using syngeneic tissues as controls. The histologic appearance of the grafts was analyzed in parallel. Preproinsulin and constant region of the TCR-beta chain transcripts were studied as markers of graft integrity and infiltrating T cell mass, respectively. The participation of certain cytokines and CTL were analyzed by the detection of IL-2, IFN-gamma, IL-4, and CTL-specific serine protease (granzyme B) transcripts. The time-related disappearance of intragraft preproinsulin transcripts correlated with graft destruction, whereas the intensity of intragraft TCR-beta chain transcript levels correlated with the magnitude of mononuclear leukocyte infiltration in allografts. In unmodified allografts, the magnitude of IL-2 and IFN-gamma intragraft mRNA levels correlated with the intense mononuclear leukocyte infiltrate found on histologic examination at day 8. Only after stable IL-2 gene transcription on day 8 does evidence of graft destruction become apparent, indicating that IL-2 gene activation is closely related to and probably required for expression of alloimmune cytopathic processes. In contrast, IL-4 transcripts were absent or detected in low copy number throughout this time course. Intragraft expression of granzyme B mRNA, a CTL-specific transcript, peaked from day 8 to day 12 in allografts compared with syngeneic grafts or normal tissue. In syngeneic grafts IL-2 and/or IL-4 mRNA was essentially not detected. Although IFN-gamma and granzyme B transcripts were detected in syngeneic grafts, after 4 days the levels of detected transcripts were far less than those noted in allografts. In vivo detection of intragraft IL-2 transcripts in the relative absence of detectable IL-4 transcripts strongly suggests IL-2-dependent immune effector mechanisms are associated with, and perhaps responsible, for allograft rejection. Apparently IL-4-dependent effector mechanisms are not necessary for allograft rejection.

Animals↗
PubMed1993

Interleukin-2 receptor-directed therapies: antibody-or cytokine-based targeting molecules.

With the exception of certain hematologic malignancies, the high affinity interleukin-2 (IL-2) receptor is only transiently expressed during the brief antigen-triggered proliferative burst of lymphocytes. Hence, we wondered whether administration of anti-IL-2 receptor (IL-2R) monoclonal antibody (mAb) or chimeric IL-2 toxins would provide a utilitarian way to achieve immunosuppression aimed directly at activated lymphocytes, or whether this approach could be used to treat IL-2R+ leukemia/lymphoma. Studies in preclinical autoimmune and transplant models indicate that this approach can be effective. The results of open, uncontrolled studies provide preliminary evidence that a chimeric IL-2 toxin is well tolerated at doses that may induce improvement in patients with IL-2R+ leukemia/lymphoma, as well as in patients with refractory rheumatoid arthritis or new-onset diabetes mellitus.

Animals↗
PubMed1992

An anergic, islet-infiltrating T-cell clone that suppresses murine diabetes secretes a factor that blocks interleukin 2/interleukin 4-dependent proliferation.

The mechanism of peripheral immunological tolerance has not been fully established. While anergic T cells have been noted in tolerant hosts, the mechanism by which they contribute to the induction and maintenance of tolerance has not been defined. As we previously reported, an accelerated form of diabetogenic autoimmunity in nonobese diabetic mice can be blocked by passive transfer of a CD3+, CD8+, beta-chain variable region 11-positive islet-infiltrating T-cell clone (IS-2.15). In this report we examine the properties of this T-cell clone. We have established that this clone is unresponsive to mitogenic concentrations of anti-T-cell receptor or anti-CD3 monoclonal antibodies and is only weakly responsive to syngeneic islet and spleen cells. Moreover, these T cells secrete an inhibitory factor(s) that irreversibly inhibits interleukin (IL) 2/IL-4-driven proliferation of IL-2/IL-4 indicator T-cell lines. This noncytotoxic factor, which possesses an apparent size of 10-30 kDa, does not interfere with low-affinity IL-2 receptor expression. These data indicate that at least some anergic T cells can play an active role in peripheral tolerance by secreting suppressor factor(s) that regulate IL-2/IL-4-dependent proliferation.

Animals↗
PubMed1992

Interleukin-2 (IL-2) induces tyrosine kinase-dependent translocation of active raf-1 from the IL-2 receptor into the cytosol.

Stimulation of the interleukin-2 (IL-2) receptor results in phosphorylation and activation of cytosolic Raf-1 serine/threonine kinase. Herein, we report that enzymatically active Raf-1 is physically associated with the IL-2 receptor beta chain (p75) in T-cell blasts. Following stimulation with IL-2, Raf-1 dissociates from the IL-2 receptor complex and translocates to the cytosol. Genistein, a protein tyrosine kinase inhibitor, prevents the dissociation of enzymatically active Raf-1 from the ligand-stimulated IL-2 receptor complex. These data favor a model of IL-2 receptor activation in which an IL-2-activated protein tyrosine kinase phosphorylates the IL-2 receptor and/or receptor-bound Raf-1. Following tyrosine phosphorylation, enzymatically active Raf-1 dissociates from the IL-2 receptor and translocates into the cytosol.

Blotting, Western↗
PubMed1992

Evidence for functional heterogeneity of rat CD4+ T cells in vivo. Differential expression of IL-2 and IL-4 mRNA in recipients of cardiac allografts.

The in vivo relevance of functional dichotomy of CD4+ Th clones was studied by analyzing the induction of mRNA encoding for Th1- (IL-2) and Th2- (IL-4) specific lymphokines in a model of accelerated (24 h) cardiac allograft (Tx) rejection in presensitized rats. The polymerase chain reaction-assisted screening of total cellular RNA from cardiac Tx of otherwise untreated sensitized recipients has revealed sequential lymphokine mRNA expression, with the peak of IL-2 mRNA (6-12 h) preceding that for IL-4 mRNA, which was maximal at the time of actual Tx loss (24 h). Both IL-2 and IL-4 transcripts could be readily detected by polymerase chain reaction analysis in the spleens during the course of accelerated rejection. Treatment of prospective cardiac Tx recipients with BWH-4, a mouse anti-rat CD4 mAb, abrogated rejection at 24 h and prolonged cardiac Tx survival to ca. 11 days, coinciding with significantly diminished IL-2 mRNA expression. In contrast, CD4 targeted therapy preserved intra-Tx and splenic transcription of the IL-4 gene. Spleen lymphocytes from mAb-conditioned recipients separated by magnetic microspheres into phenotypically distinct subpopulations, showed differential induction of IL-2 and IL-4 mRNA. Thus, IL-2 mRNA was at most very weakly expressed, whereas IL-4 transcription was strongly induced both in CD4+ T cells and its OX-22- subset. This study demonstrates the induction of IL-4 mRNA in situ in the rat system, describes discordant elaboration of IL-2 and IL-4 mRNA in untreated/anti-CD4 mAb-treated cardiac Tx recipients, and identifies OX-22- CD4+ T cells as the IL-4 mRNA producers. Thus, these results provide evidence for functional heterogeneity of rat CD4+ T cells in vivo, as defined by divergent mRNA lymphokine transcription profiles.

Animals↗