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W W Hancock

Publications and source records attributed to W W Hancock.

At least 127 records · Page 7Linked to original sources
PubMed1995

CD28-B7 blockade after alloantigenic challenge in vivo inhibits Th1 cytokines but spares Th2.

Blocking the CD28-B7 T cell costimulatory pathway with the fusion protein CTLA4Ig inhibits alloimmune responses in vitro and in vivo and induces tolerance to cardiac allografts in mice and rats, but the mechanisms mediating the tolerant state in vivo are unknown. Here, we report the effects and potential mechanisms of CTLA4Ig in the rat renal allograft model. LEW rats were nephrectomized and received renal allografts from major histocompatibility complex-incompatible WF rats. While all untreated and control immunoglobulin (Ig)-treated animals acutely rejected their allografts and died, 86% of rats that received a single injection of CTLA4Ig on day 2 after transplantation had prolonged survival (> 60-100 days) with preserved renal function. By contrast, only 29% of animals that received CTLA4Ig on the day of engraftment had prolonged survival. Long-term survivors (> 100 days) exhibited donor-specific tolerance, accepting donor-matched WF but acutely rejecting third-party BN cardiac allografts. Immunohistological analysis of grafts sampled at 1 week after transplantation showed that both control and CTLA4Ig-treated animals had mononuclear cell infiltrates, with a higher percentage of CD4+ cells in the CTLA4Ig-treated group. However, while this was associated with vasculitis and tubulitis in control grafts, there was no evidence of tissue injury in CTLA4Ig-treated animals. The immune response leading to graft rejection in control animals was characterized by expression of the T helper (Th) type 1 cytokines interleukin (IL)-2 and interferon-gamma. In contrast, the persistent CD4+ infiltrate without graft rejection in CTLA4Ig-treated animals was associated with increased staining for the Th2-related cytokines IL-4 and IL-10. Furthermore, grafts from CTLA4Ig-treated animals had marked upregulation of intragraft staining for IgG1, but not IgG2a or IgG2b. Administration of rIL-2 to CTLA4Ig-treated animals restored allograft rejection in 50% of animals tested. These results confirm that blockade of the CD28-B7 pathway after alloantigenic challenge induces donor-specific acceptance of vascularized organ allografts, and indicates in this model that CTLA4Ig inhibits Th1 but spares Th2 cytokines in vivo.

Abatacept↗
PubMed1995

Upregulation of cytokines associated with macrophage activation in the Lewis-to-F344 rat transplantation model of chronic cardiac rejection.

Lewis-to-F344 rat cardiac allografts develop chronic rejection and arteriosclerotic lesions rich in mononuclear cells (especially macrophages). This study was performed to determine whether cytokine pathways associated with macrophage activation are upregulated in hearts undergoing chronic rejection. Gene transcript levels for IFN-gamma, monocyte chemoattractant protein-1 (MCP-1), and IL-6 were measured with reverse-transcription PCR assays optimized for each gene. Gene products were confirmed by immunohistology. For all three genes, transcript levels in rat cardiac allografts increased significantly on day 7 and remained elevated on days 14 and 28 posttransplantation, as compared with naive hearts, paired host hearts, and syngrafts (P < 0.006). For the inducible genes IFN-gamma and MCP-1, high transcript levels in cardiac allografts were in contrast with low levels in host spleens. On the other hand, transcript levels for the basally expressed gene IL-6 were elevated in both organs. Immunostaining confirmed allograft-specific expression for all three cytokines and localized the gene products to infiltrating mononuclear cells in the interstitium and vasculature. The sustained expression of these cytokines in cardiac allografts undergoing chronic rejection supports the widely held hypothesis that the intimal changes associated with transplant arteriosclerosis are mediated by cellular activation and cytokine production.

Animals↗
PubMed1995

Increased expression of IL-4 and IL-10 and decreased expression of IL-2 and interferon-gamma in long-surviving mouse heart allografts after brief CD4-monoclonal antibody therapy.

In a mouse model for vascularized heart transplantation, CBA recipients of BALB/c hearts were treated with 0.25 mg of anti-CD4 (GK1.5) given intraperitoneally on the day of grafting and on days 1, 2, and 3 thereafter. This reduced splenic CD4+ cells to < 1% and all grafts survived > 100 days, compared with 8-10 days in untreated recipients. Despite recovery of the CD4+ cells after day 21, mice did not reject donor-type skin grafts at > 30 days, but rapidly rejected third-party skin, showing alloantigen-specific tolerance. The surviving heart grafts had significant mononuclear cell infiltration at time points from 7 to 100 days after transplantation. In the normal rejection process, where extensive myocyte necrosis was seen at 7 days, graft-infiltrating T cells produced IL-2 and IFN-gamma. These cells responded in vitro to IL-2 and displayed donor-specific CTL activity. In contrast, cells from CD4-mAb-treated hearts did not show significant growth in IL-2 or kill donor cells in CTL assays. In these nonrejecting hearts, immunohistology showed a diffuse infiltrate of T cells and macrophages by day 3. The allograft infiltrate increased rapidly thereafter in both rejecting and nonrejecting grafts, peaking at day 6-7 in rejecting grafts, when CD4+, CD8+, and IL-2R+ cells were present, with expression of IL-2, IFN-gamma, and IL-4, but only trace levels of IL-10. From 14 to 100 days, nonrejecting allografts showed a characteristic cytokine profile of dense IL-4 and IL-10 expression on intragraft leukocytes and endothelial cells, with low levels of IL-2 and IFN-gamma. This cytokine profile, characteristic of Th2 responses, was seen in all nonrejecting grafts and was not present in rejecting grafts. Allograft tolerance can studied by examination of the functions and cytokine profile of the cells within the graft, and tolerance develops in the presence of a Th2 response within the graft.

Animals↗
PubMed1995

The alloantibody network following intrathymic immunomodulation of sensitized rat recipients of cardiac allografts.

An intrathymic injection of allogeneic spleen cells (2 x 10(7)) prevents accelerated (< 36 hr) rejection in sensitized LEW rats, and prolongs the survival of LBNF1 cardiac allografts to about 11 days. This effect is donor-specific, x-irradiation-sensitive and thymus-dependent, and it does not require adjunctive immunosuppressive therapy. We have recently shown that following intrathymic allo-Ag injection, host cell proliferative responses in lymphoid organs are markedly depressed as compared with untreated sensitized recipients. Little is known about how intrathymic immunomodulation may affect host humoral alloreactivity. In this work, we studied the dynamic interplay between the humoral responses, both in the circulation and at the graft site of sensitized hosts. Intrathymic allo-Ag exposure triggered a profound change in the utilization pattern of alloreactive IgM, IgG, and IgG subclasses compared with recipients receiving syngeneic cells. Administration of allo-Ag into the thymus at the time of sensitization resulted in an earlier and significantly increased systemic production of IgM, as shown by flow cytometry. Subsequently, isotype switching to IgG occurred prematurely and resulted in elevated levels of IgG1 and IgG2a. Indeed, the addition of such allo-Ab enriched serum suppressed the MLR assay in a dose-dependent manner. The binding of Ig to cardiac allografts was analyzed in eluates by flow cytometry, and by immunohistochemical staining at day 1 after transplantation. Intragraft IgM and IgG levels were consistently higher in well-functioning grafts following administration of allo-Ag, as compared with controls. IgG deposits at the graft site consisted predominantly of IgG1 and IgG2a, while significant amounts of IgG2b could only be detected in control hosts undergoing accelerated graft rejection. These data document that intrathymic injection of donor-specific allo-Ag in sensitized recipients leads to profound alterations of the host humoral alloresponses, and that such elevated allo-Ab levels interfere with the Ag reactivity or alloresponsive effector cells in vitro. These results support the notion that the pattern of allo-Ab utilization is indicative of the functional status of the alloimmune response in the transplant recipient.

Animals↗
PubMed1995

alpha/beta-T cell receptor-directed therapy in rat cardiac allograft recipients. Treatment prior to alloantigen exposure prevents sensitization and abrogates accelerated rejection.

An mAb directed to the alpha/beta-heterodimer of the rat T cell receptor was used to prevent rejection of cardiac allografts in sensitized (accelerated rejection) recipients. Over a wide dose range, alpha/beta-TCR-directed therapy abrogated accelerated rejection at 24-36 hr and extended cardiac allograft survival in a dose-dependent fashion, both when given after heart transplantation as well as during or before the sensitizing skin transplants (8.9 +/- 1.0 days, 12.7 +/- 0.6 days, or 8.7 +/- 1.5 days, respectively). Pretreatment with R73 completely abrogated host sensitization induced by skin grafting. As a result, post-heart transplant cyclosporine course (15 mg/kg for 7 day) has led to long-term graft acceptance (> 90 days vs. 15.2 +/- 1.6 days with postoperative CsA therapy alone). Administration of R73 mAb produced incomplete depletion (CD5+ cells) and partial modulation (alpha/beta-TCR/CD5 double-positive cells) in the peripheral blood. It suppressed in situ protein expression of many cytokines to background levels, in particular that of IL-2 and IFN-gamma, both when given after as well as before cardiac transplantation. However, only pretransplant mAb application was associated with augmented in situ elaboration of IL-4. alpha/beta-TCR-directed therapy induced strong host anti-idiotypic and, to a lesser degree, anti-isotypic antibody responses. Taken together, these results provide the rationale for a novel immunosuppressive strategy involving induction of hyporesponsiveness by alpha/beta-TCR-directed therapy before the alloantigenic exposure.

Animals↗
PubMed1995

Role of endothelial cells in transplantation.

Endothelial cell activation with accompanying vascular inflammatory changes is considered central to the experimental manifestations of both hyperacute and delayed xenograft rejection responses. Natural xenoreactive antibodies directed at alpha-galactosyl residues of xenogeneic glycoproteins and glycolipids, with associated complement activation via the classical pathway, are considered major immediate mediators of graft endothelial cell injury in the clinically relevant discordant swine to primate combinations. In delayed xenograft rejection processes, where recipients are treated prophylactically to ameliorate these initial events, activation of infiltrating mononuclear phagocytes and natural killer cells are associated with ongoing endothelial cell activation processes, procoagulant generation and vascular thrombosis. Allograft hyperacute rejection is observed when vascularised organs are transplanted to sensitized individuals with high levels of cytotoxic antibodies. Less dramatic forms of humoral allograft rejection (termed accelerated or vascular rejection) and the more common cell-mediated endothelialitis are associated with significant graft damage. Endothelial cell activation is also linked with graft preservation injury, forms of chronic rejection and delayed graft loss. Experimental work is currently being directed at the control of hyperacute rejection, the close understanding of endothelial cell thromboregulation in both transplanted xeno- and allografts and the development of novel therapeutic agents including gene therapy and the possible use of organs from transgenic animals.

Cell Transplantation↗
PubMed1995

Blocking cell microtubule assembly inhibits the alloimmune response in vitro and prolongs renal allograft survival by inhibition of Th1 and sparing of Th2 cell function in vivo.

Colchicine inhibits cell microtubule assembly by binding to and preventing the polymerization of tubulin monomers. Although there are data to indicate that colchicine inhibits a variety of cell-mediated immune responses, the effects and mechanisms of inhibiting cell microtubule assembly on the alloimmune response have not been thoroughly investigated. It has recently been shown that colchicine prevents acute rejection and promotes the long-term survival of rat renal allografts. In this study, the effects and mechanisms of inhibiting cell microtubule assembly by colchicine on the alloimmune response in vitro and in vivo were examined. First, the effects of colchicine on T lymphocyte response to alloantigen in vitro were tested. In the standard one-way mixed lymphocyte response (MLR), responder Lewis rat lymph node cells were cultured with irradiated Brown-Norway stimulators. Colchicine inhibited the MLR in a dose-dependent manner, with 100% inhibition at a concentration of 25 ng/mL (6.25 x 10(-8) M) and 50% inhibition at a concentration of approximately 5 to 10 ng/mL. Colchicine also inhibited the generation of cytotoxic T lymphocytes as well as cytotoxic T cell effector function in vitro in a dose-dependent fashion. Second, detailed immunohistologic studies of renal allografts harvested from unmodified control (acutely rejecting) and colchicine-treated rats (Day 15 or 30) were performed. These studies showed that grafts from colchicine-treated animals had significantly fewer mononuclear cell infiltrates and less edema, and moderately decreased deposition of immunoglobulin M, C3, and fibrin, as compared with acutely rejecting control grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Suppression of insulitis in non-obese diabetic (NOD) mice by oral insulin administration is associated with selective expression of interleukin-4 and -10, transforming growth factor-beta, and prostaglandin-E.

Oral administration of autoantigens suppresses development of autoimmunity in several animal models, and is being tested in clinical trials in patients with autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. Non-obese diabetic (NOD) mice spontaneously develop insulin-dependent diabetes mellitus at 15 to 20 weeks of age, after mononuclear cell (MNC) infiltration of the pancreatic islets of Langerhans and destruction of insulin-producing beta cells. We have previously shown that oral administration of insulin suppresses insulitis and development of diabetes in the NOD mouse. Oral insulin has no metabolic effect on blood glucose. Oral insulin mediates its effect through a T cell-dependent mechanism as shown by adoptive transfer and T cell depletion experiments, but the mechanisms responsible have not been fully explored. We now report a serial analysis of the cells and cytokines associated with development of diabetes in NOD mice, and contrast this with the findings in animals fed equine insulin or a control protein (ovalbumin). Animals were fed 1 mg twice a week for 5 weeks, beginning at 5 weeks of age. Marked insulitis in naive or ovalbumin-fed NOD mice occurred at 10 weeks, at which time a dense peri-islet and intra-islet MNC infiltration was observed. Immunohistological studies using monoclonal antibodies showed that infiltrating MNC consisted mainly of CD4+ T cells ( > 75% of leukocytes) plus smaller numbers of macrophages and CD8+ T cells. These cells displayed evidence of immune activation with expression of receptors for interleukin-2 (IL-2R) plus Th1 cytokines; dense labeling for IFN-gamma and tumor necrosis factor-alpha, plus lesser amounts of IL-2, was observed. MNC lacked labeling for IL-4, IL-10, prostaglandin-E, or transforming growth factor-beta. By contrast, at 10 weeks, pancreatic tissues from NOD mice fed insulin showed considerably less insulitis, and the residual MNC, although still largely CD4+ T cells plus macrophages, showed dense labeling for IL-4, IL-10, prostaglandin-E, and transforming growth factor-beta and an absence of IL-2, IFN-gamma or tumor necrosis factor-alpha Taken together with our previous findings, these data indicate that oral administration of insulin affects the development of diabetes in NOD mice through the generation of cells that elaborate immunoregulatory cytokines within the target organ and shift the balance from a Th1 to a Th2 pattern of cytokine expression.

Administration, Oral↗
PubMed1995

Up-regulation of endothelin-1 mRNA and peptide expression in rat cardiac allografts with rejection and arteriosclerosis.

Acute and chronic rejection are frequent and significant complications of cardiac transplantation, and graft arteriosclerosis is the leading cause of death beyond the first year after transplant. Levels of endothelin-1 (ET-1) are elevated in plasma of patients with cardiac allografts and those with symptomatic vascular atherosclerosis, but little is known about the role of ET-1 in these processes. This study examined intragraft ET-1 expression in rat cardiac models of acute rejection and chronic rejection associated with graft arteriosclerosis. Corrected ET-1 gene transcript levels were measured with a [32P]dCTP reverse transcription polymerase chain reaction assay normalized with glyceraldehyde-3-phosphate dehydrogenase, and the gene product was evaluated by immunohistology with a monospecific anti-ET-1 antibody at different time points after transplant. ET-1 mRNA levels were significantly increased in acutely rejected (Wistar-Furth rat cardiac allografts transplanted into Lewis rat recipients) and chronically rejected (Lewis allografts transplanted into F344 recipients) vascularized cardiac allografts as compared with isograft controls. In acutely rejected allografts, peak expression occurred on day 5 after transplant. In chronically rejected allografts, the increase in ET-1 mRNA was sustained on days 7, 28, and 75. In both acutely and chronically rejected allografts, ET-1 mRNA upregulation was not seen in host spleens or paired host hearts. Immunohistological analysis confirmed that the bulk of ET-1 peptide expression was localized to mononuclear cells that diffusely infiltrated the graft interstitium (acute rejection and early chronic rejection) and accumulated within the neointima of chronically rejecting hearts with arteriosclerosis. These observations, taken together with in vitro data showing that ET-1 production is stimulated by certain cytokines, indicate that the allogeneic stimulus within rejecting vascularized cardiac allografts, presumably cytokine mediated, leads to significant intragraft up-regulation of ET-1 mRNA and peptide expression. The local up-regulation of this vasoactive and mitogenic peptide within acutely and chronically rejected cardiac allografts suggests that ET-1 may be involved in the development of graft arteriosclerosis.

Animals↗