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Biomedical subjects

S M Stepkowski

Publications and source records attributed to S M Stepkowski.

At least 73 records · Page 4Linked to original sources
PubMed1994

Blocking of heart allograft rejection by intercellular adhesion molecule-1 antisense oligonucleotides alone or in combination with other immunosuppressive modalities.

Intercellular adhesion molecule-1 (ICAM-1) binds circulating leukocytes through interactions with beta 2 integrins, LFA-1, and macrophage Ag-1. The phosphorothioate antisense oligodeoxynucleotide, IP-3082, specific for ICAM-1 mRNA inhibited ICAM-1, but not vascular cell adhesion molecule-1, mRNA induction and expression of ICAM-1 molecules by mouse endothelioma cells. Scrambled control oligonucleotides were ineffective. Untreated C3H (H-2k) mice rejected C57BL/10 (H-2b) heart allografts with a mean survival time of 7.7 +/- 1.4 days. Administration i.v. of IP-3082 by a 7-day osmotic pump prolonged the survival of heart allografts in a dose-dependent fashion: 1.25 mg/kg, to 11 +/- 0 days; 2.5 mg/kg, to 12 +/- 2.7 days; 5 mg/kg, to 14.1 +/- 2.7 days; and 10 mg/kg, to 15.3 +/- 5.8 days (all p < 0.01). Control IP-1082 (10 mg/kg) was ineffective (7 +/- 0.8 days). Although 7-day anti-LFA-1 mAb (50 micrograms/day; i.p.) prolonged allograft survival to 14.1 +/- 2.7 days, the addition of IP-3082 (5.0 mg/kg x 7 days) induced donor-specific transplantation tolerance (> 150 days). Furthermore, IP-3082 (5 mg/kg x 7 days) acted synergistically with antilymphocyte serum, rapamycin, and brequinar, but not cyclosporin A: a single antilymphocyte serum (0.2 ml) i.p. injection alone prolonged graft survival to 10 +/- 0.5 days (p < 0.01) and in combination with IP-3082 (5 mg/kg), to 32.2 +/- 8.3 days (p < 0.001); rapamycin (0.1 mg/kg x 7 days; i.v.) alone prolonged survival to 13 +/- 7.5 days (p < 0.01), and with IP-3082, to 32.4 +/- 8.9 days (p < 0.03); brequinar (0.5 mg/kg x 7 days; oral gavage) alone to 12 +/- 2.4 days (p < 0.05), and with IP-3082 (5 mg/kg), to 38.8 +/- 30.2 days (p < 0.01); in contrast, cyclosporin A (5 mg/kg x 7 days; i.v.) alone produced graft survival of 9.8 +/- 1.3 days (p < 0.1 and in combination with IP-3082 (5 mg/kg), produced survival of 7.8 +/- 3.5 days (NS). Thus, antisense oligonucleotides may proffer a selective gene-targeted immunosuppressive therapy for organ transplantation.

Animals↗
PubMed1994

Rapamycin inhibits production of cytotoxic but not noncytotoxic antibodies and preferentially activates T helper 2 cells that mediate long-term survival of heart allografts in rats.

Rapamycin (RAPA) induces unresponsiveness toward heart allografts by at least two mechanisms: selective production of noncytotoxic IgG2c-blocking Ab and preferential activation of Th2 cells. RAPA (0.8 mg/kg/day) delivered via a 14-day osmotic pump to Wistar Furth (WF; RT-1u) recipients prolongs Buffalo (BUF; RT-1b) heart allograft survival from a mean survival time (MST) of 6.5 +/- 0.5 days to 75.0 +/- 18.9 days (n = 18; p < 0.001), with 6 of 18 grafts beating for more than 100 days. Recipient sera or their IgG but not IgM fraction, obtained after postgrafting day 40, passively transfer the unresponsive state to sublethally irradiated secondary recipients in a dose-dependent and immunologically-specific fashion. Sera obtained after untreated WF hosts rejected BUF hearts contained IgG moieties of all subclasses that bound to class I MHC BUF epitopes. In contrast, the unresponsive sera contained predominantly non-C'-fixing IgG2c and only marginal amounts of activated (C') fixing IgG1, IgG2a, and IgG2b Ab. The transcription of IL-2, IL-4, and IL-10 mRNAs was assessed using a PCR method. There were similar increases in the levels of IL-2, IL-4, and IL-10 mRNA in heart allografts from both untreated and RAPA-treated recipients on day 5 postgrafting. In contrast, on days 60 and 300 postgrafting heart allografts from RAPA-treated unresponsive recipients showed increased levels of IL-10 and IL-4 but not of IL-2 mRNA, suggesting preferential activation of Th2 cells. Thus, RAPA treatment selectively inhibits the synthesis of C'-binding of IgG subclasses, spares the non C-binding blocking IgG2c Ab, and preferentially activates Th2 cells.

Animals↗
PubMed1994

Transplantation immunobiology. An update.

Transplantation of allografts is hampered by immunologic destruction. Alloantigens are recognized directly as intact molecules expressed on the graft or indirectly as allopeptides following processing and presentation by antigen presenting cells. This article describes new information regarding the immune response to alloantigens.

Animals↗
PubMed1993

The mechanism of unresponsiveness to allografts induced by rapamycin and rapamycin/cyclosporine treatment in rats.

The mechanisms by which rapamycin (RAPA) and/or cyclosporine induce unresponsiveness to allografts were investigated in a rat model. Buffalo (BUF, RT-1b) heart allografts were rejected by Wistar-Furth (WFu, RT-1u) recipients at a mean survival time (MST) of 6.5 +/- 0.5 days. A 14-day course of RAPA (0.8 mg/kg) delivered intravenously by an osmotic pump prolonged BUF allograft survival to 76.1 +/- 23.4 days (P < 0.001). Adoptive transfer of 30-50 x 10(6) spleen and lymph node T cells that had been isolated on day 40 postgrafting from CsA- or RAPA/CsA-treated hosts into lightly irradiated (6 Gray) secondary WFu recipients prolonged BUF graft survival from 9.8 +/- 1.2 to 29.2 +/- 11.0 (P < 0.01) and 58.2 +/- 38.9 days (P < 0.004), respectively. T cells transferred from animals treated with RAPA alone failed to prolong graft survival. In contrast, sera isolated on day 40 postgrafting from WFu primary hosts treated with RAPA alone or with the RAPA/CsA combination, but not with CsA alone, extended the survival of BUF hearts: 3 ml serum from RAPA-treated hosts prolonged BUF heart survival to 76.6 +/- 31.3 days (P < 0.002) and from RAPA/CsA-treated hosts to 47.1 +/- 12.8 days (P < 0.001). The effect of serum was immunologically specific: it did not prolong the survival of third-party outbred Sprague Dawley heart allografts. Although the IgM fraction (0.2 mg) purified from the serum of RAPA-treated recipients was ineffective (10.6 +/- 0.8 days; NS), an equal amount of the IgG fraction significantly (P < 0.002) prolonged BUF heart allograft survival to 26 days (n = 4). Thus, hosts treated with RAPA or a RAPA/CsA combination develop IgG antibodies that mediate the unresponsive state toward allogeneic heart allografts.

Animals↗
PubMed1993

Immunosuppressive effects of defibrotide.

The effect of defibrotide (DF) alone or in combination with CsA was examined using in vitro proliferation assays with human PBLs and in vivo heterotopic heart allografts in rats. DF alone (12.5-50 mg/ml) inhibited in vitro PBL proliferation more effectively after PHA (50-56%) or OKT3 (50-95%), than after alloantigenic (25-30%), stimulation. Furthermore, the combination of DF (1-4 mg/ml) with CsA (10-40 ng/ml) caused an 85.2-86.8% reduction in proliferative responses after OKT3 stimulation. Median-effect analysis documented that the combination index for DF and CsA was consistently lower than 0.3 at various concentration ratios of the 2 agents. Combination index values below 1.0 reflect drug synergism; those equal to 1.0 show additive, and above 1.0, antagonistic, interactions. Daily intraperitoneal injections of DF (150 mg/kg) failed to prolong the survival of Buffalo (RT-1b) heart allografts in Wistar-Furth (RT-1u) recipients, namely mean survival times of 7.0 +/- 0.7 days with, vs. 6.5 +/- 0.5 days without, DF treatment. Similarly, intravenous or intra-arterial infusion of DF (280 mg/kg) delivered directly into the heart allograft by a 7-day osmotic pump was ineffective. However, a course of local, but not systemic, DF (280 mg/kg) combined with a 14-day i.v. administration of a subtherapeutic dose of CsA (1 mg/kg) significantly prolonged heart allograft survival to 22.8 +/- 5.0 days (P < 0.001). Thus, in vitro DF is immunosuppressive alone at high concentrations, and in combination with CsA at low concentrations. Continuous infusion of DF into the graft combined with systemic administration of CsA prolonged transplant survival in vivo. These findings suggest that high tissue levels of DF potentiate the immunosuppressive effects of CsA.

Animals↗