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M Sykes

Publications and source records attributed to M Sykes.

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

IL-2-induced GVHD protection is not inhibited by cyclosporine and is maximal when IL-2 is given over a 25 h period beginning on the day following bone marrow transplantation.

We have recently demonstrated, in a fully MHC-mis-matched murine bone marrow transplantation (BMT) model, that administration of a short course of high-dose interleukin 2 (IL-2) markedly delays the onset of graft-versus-host disease (GVHD) without compromising alloengraftment or the graft-versus-leukemia (GVL) effect of allogeneic T cells. Early timing of IL-2 administration and high dose were shown to be critical to achieve this protective effect. Although a 2.5 day course of IL-2, begun on the day of BMT, was found to confer marked protection without observable toxicity, shorter courses and a higher dose of IL-2 than 5 x 10(4) Cetus units per treatment have not been previously evaluated in this model. We now demonstrate that administration of a three-treatment course of IL-2 over a 25 h period beginning 15 h following BMT is sufficient to provide maximal GVHD protection, that increasing the IL-2 dose beyond 5 x 10(4) units per treatment does not further improve the level of GVHD protection, and that further division of IL-2 treatments to achieve more constant tissue levels does not result in improved GVHD protection. We also demonstrate that IL-2 is still protective when administered in combination with cyclosporine. These results suggest that IL-2 administered in a sufficient short course to avoid toxicity might have the potential to achieve effective GVHD prophylaxis in humans, even if given in combination with cyclosporine.

Animals↗
PubMed1994

IL-2 inhibits early increases in serum gamma interferon levels associated with graft-versus-host-disease.

We have recently demonstrated that a short course of high-dose IL-2 administered to lethally irradiated mice leads to marked protection from early and late GVHD mortality, especially when T cell-depleted (TCD) host-type bone marrow cells (BMC) are also administered. IL-2 inhibits the GVHD-inducing activity of donor CD4+ cells without inhibiting their graft-vs.-leukemia effects. Since CD4+ T-lymphocytes produce a variety of cytokines, some of which have recently been implicated in the pathogenesis of GVHD, we have studied the possible effect of IL-2 administration on serum levels of various cytokines. Acute GVHD was induced in lethally irradiated B10 mice by bone marrow transplantation (BMT) with MHC-mismatched allogeneic (A/J) BMC and splenocytes. TCD B10 (host-type) BMC were coadministered to maximize the protective effect of IL-2. Serum cytokine levels were compared in recipients of these inocula with or without a protective course of IL-2 treatment. A marked increase in serum IFN-gamma levels was noted on days 3 through 5 post-BMT in GVHD mice compared with syngeneic BMT control recipients. This GVHD-induced rise in serum IFN-gamma was markedly inhibited in IL-2-protected mice. Murine IL-2 levels were only slightly increased in sera of GVHD mice, and were not influenced by treatment with human recombinant IL-2. Serum levels of the monokines TNF-alpha and IL-1 alpha showed variable early elevations in GVHD mice with or without IL-2 treatment, and were not different from levels observed in syngeneic controls. Serum levels of IFN-gamma, IL-1 alpha, and TNF-alpha all declined markedly by day 7 to 8 post-BMT, when GVHD mortality begins. Administration of neutralizing anti-IFN-gamma mAb did not attenuate and tended to accelerate GVHD mortality, and administration of exogenous IFN-gamma did not overcome the protective effect of IL-2 against GVHD. Together, our results indicate that GVHD is associated with high serum levels of several proinflammatory cytokines in the first week post-BMT, but that these levels decline by the time when GVHD mortality begins. IL-2 specifically inhibits the GVHD-associated production of IFN-gamma, but this inhibition in itself does not explain and may even mitigate the protective effect of IL-2 against early GVHD mortality. However, the demonstration that IL-2 markedly inhibits the production of a GVHD-associated cytokine raises the possibility that alterations in the production of as yet undefined cytokines may be responsible for IL-2-induced GVHD protection.

Animals↗
PubMed1994

Specific tolerance across a discordant xenogeneic transplantation barrier.

Successful induction of tolerance across disparate (discordant) species barriers could overcome the organ shortage that presently limits clinical transplantation. We demonstrate here that xenogeneic swine thymic transplants can induce tolerance to swine antigens in mice, while positively selecting functional host CD4+ T cells. Immunologically normal C57BL/10 mice were thymectomized and depleted of T and natural killer cells; then they received transplants of fetal pig thymus and liver fragments. Mature mouse CD4+ T cells developed in the pig thymus grafts and migrated to the periphery. Swine grafts grew markedly and no anti-pig IgG response was produced. Mixed lymphocyte reactions confirmed that the new T cells were functional and were tolerant to pig antigens.

Animals↗
PubMed1994

Role of intrathymic clonal deletion and peripheral anergy in transplantation tolerance induced by bone marrow transplantation in mice conditioned with a nonmyeloablative regimen.

We have investigated the mechanism of tolerance induced by allogeneic bone marrow transplantation (BMT) in mice conditioned with a nonmyeloablative regimen. Permanent mixed chimerism and skin allograft tolerance were achieved when recipient B10 (H-2b) mice were pre-treated with anti-CD4 and anti-CD8 mAbs, thymic irradiation, and 3 Gy whole body irradiation, followed by injection of B10.A (H-2a) bone marrow cells. V beta 11+ T cells are normally deleted in I-E+ B10.A mice, but not in I-E- B10 mice. In spleens of mixed B10.A-->B10 chimeras, V beta 11+ B10 T cells were reduced but detectable in the first 6 wk after BMT, and later became undetectable. Splenic V beta 11+ T cells were unresponsive to receptor cross-linking with V beta 11-specific mAb, demonstrating anergy. B10 V beta 11+ T cells were also detected in spleens of mice that were thymectomized before BMT. In PBL of chimeras, V beta 11+ T cells were undetectable for at least 1.5 yr. Thymocyte chimerism and extensive clonal deletion of mature V beta 11+ B10 thymocytes were observed as early as 10 days post-BMT and at all subsequent time points in thymi of mixed chimeras. Rare I-E+ donor cells were detected in day 10 thymi, and these increased progressively in frequency at later times. In chimeras prepared in the reciprocal strain combination, B10-->B10.A, B10 donor V beta 11+ T cells were undetectable in PBL. Together, our results implicate both central clonal deletion and peripheral clonal anergy in tolerance induced with our regimen. A very low number of intrathymic donor cells or low density of Ag expression is sufficient to mediate extensive clonal deletion of thymocytes that recognize donor Ags.

Animals↗
PubMed1994

Interleukin-2 inhibits graft-versus-host disease-promoting activity of CD4+ cells while preserving CD4- and CD8-mediated graft-versus-leukemia effects.

We have recently shown that a short course of high-dose interleukin-2 (IL-2) can markedly inhibit the graft-versus-host disease (GVHD)-promoting activity of donor CD4+ T cells. The difficulty in dissociating GVHD-promoting from graft-versus-leukemia (GVL) effects of alloreactive donor T cells currently prevents clinical bone marrow transplantation (BMT) from fulfilling its full potential. To test the capacity of IL-2 treatment to promote such a dissociation, we have developed a new murine transplantable acute myelogenous leukemia model using a class II major histocompatibility complex-positive BALB/c Moloney murine leukemia virus-induced promonocytic leukemia, 2B-4-2. BALB/c mice receiving 2.5 x 10(5) 2B-4-2 cells intravenously 1 week before irradiation and syngeneic BMT died from leukemia within 2 to 4 weeks after BMT. Administration of syngeneic spleen cells and/or a 2.5-day course of IL-2 treatment alone did not inhibit leukemic mortality. In contrast, administration of non-T-cell-depleted fully allogeneic B10 (H-2b) spleen cells and T-cell-depleted B10 marrow led to a significant delay in leukemic mortality in IL-2-treated mice. In these animals GVHD was inhibited by IL-2 treatment. GVL effects were mediated entirely by donor CD4+ and CD8+ T cells. Remarkably, IL-2 administration did not diminish the magnitude of the GVL effect of either T-cell subset. This was surprising, because CD4-mediated GVHD was inhibited in the same animals in which CD4-mediated GVL effects were not reduced by IL-2 treatment. These results suggest a novel mechanism by which GVHD and GVL effects of a single unprimed alloreactive T-cell subset can be dissociated; different CD4 activities promote GVHD and GVL effects, and the former, but not the latter activities are inhibited by treatment with IL-2.

Animals↗
PubMed1994

The importance of nonimmune factors in reconstitution by discordant xenogeneic hematopoietic cells.

Bone marrow transplantation has been shown to induce donor-specific tolerance in rodent models. This approach could potentially be applied to xenotransplantation across discordant species barriers. To evaluate host factors resisting hematopoietic cell engraftment, we have developed two model systems utilizing the combination of swine into severe combined immunodeficient (SCID) mice. SCID mice lack functional B and T lymphocytes, and can therefore be used to evaluate nonimmune factors resisting marrow engraftment, and for adoptive transfer studies to test the role of immune cells and antibodies. First we transplanted swine bone marrow cells into SCID mice conditioned with whole-body irradiation (4 Gy). For nine weeks following the intravenous administration of 10(8) swine bone marrow cells, up to 3.8% of peripheral blood leukocytes were of swine origin, as determined by flow cytometry (FCM). These cells were all of the myeloid lineage. Swine IgG was also detectable in the serum for up to 14 weeks. The bone marrow of the reconstituted mice contained low percentages of swine myeloid cells, and swine myeloid progenitors could be detected for up to 20 weeks after bone marrow transplantation. In a second model, we grafted thymus and liver tissue from 45-69-day-old swine fetuses under the kidney capsule of 4 Gy-irradiated SCID mice. A suspension containing 10(8) swine fetal liver cells (FLC) was also administered i.p. Long-term repopulation with swine T cells was observed, with up to 1.5% swine T cells detected in the WBC, peritoneum, and spleen for at least 5.5 months postgrafting. These T cells expressed either CD4 or CD8, whereas up to 17.6% of cells in the thymic grafts expressed both CD4 and CD8. The i.p. FLC suspension was required for optimal long-term graft maintenance. Our studies show that (1) low level myeloid and B lymphocyte reconstitution can be achieved by transferring adult swine BMC to irradiated SCID recipients; (2) swine myeloid progenitors were detectable long-term in BMC of these mice, suggesting that stem cell engraftment was achieved; and (3) T cell reconstitution of SCID mice by swine progenitors requires cotransplantation of a swine stromal environment, as is provided by fetal swine thymus/liver grafts. We conclude that nonimmune factors such as those provided by species-specific stromal environments are important for reconstitution of some lineages by discordant hematopoietic stem cells.

Animals↗
PubMed1994

Myelosuppressive conditioning is required to achieve engraftment of pluripotent stem cells contained in moderate doses of syngeneic bone marrow.

We have investigated the requirement for whole body irradiation (WBI) to achieve engraftment of syngeneic pluripotent hematopoietic stem cells (HSCs). Recipient B6 (H-2b; Ly-5.2) mice received various doses of WBI (0 to 3.0 Gy) and were reconstituted with 1.5 x 10(7) T-cell-depleted (TCD) bone marrow cells (BMCs) from congenic Ly-5.1 donors. Using anti-Ly-5.1 and anti-Ly-5.2 monoclonal antibodies and flow cytometry, the origins of lymphoid and myeloid cells reconstituting the animals were observed over time. Chimerism was at least initially detectable in all groups. However, between 1.5 and 3 Gy WBI was the minimum irradiation dose required to permit induction of long-term (at least 30 weeks), multilineage mixed chimerism in 100% of recipient mice. In these mice, stable reconstitution with approximately 70% to 90% donor-type lymphocytes, granulocytes, and monocytes was observed, suggesting that pluripotent HSC engraftment was achieved. About 50% of animals conditioned with 1.5 Gy WBI showed evidence for donor pluripotent HSC engraftment. Although low levels of chimerism were detected in untreated and 0.5-Gy-irradiated recipients in the early post-BM transplantation (BMT) period, donor cells disappeared completely by 12 to 20 weeks post-BMT. BM colony assays and adoptive transfers into secondary lethally irradiated recipients confirmed the absence of donor progenitors and HSCs, respectively, in the marrow of animals originally conditioned with only 0.5 Gy WBI. These results suggest that syngeneic pluripotent HSCs cannot readily engraft unless host HSCs sustain a significant level of injury, as is induced by 1.5 to 3.0 Gy WBI. We also attempted to determine the duration of the permissive period for syngeneic marrow engraftment in animals conditioned with 3 Gy WBI. Stable multilineage chimerism was uniformly established in 3-Gy-irradiated Ly-5.2 mice only when Ly-5.1 BMC were injected within 7 days of irradiation, suggesting that repair of damaged host stem cells or loss of factors stimulating engraftment may prevent syngeneic marrow engraftment after day 7.

Animals↗
PubMed1994

Strain dependence of interleukin-2-induced graft-versus-host disease protection: evidence that interleukin-2 inhibits selected CD4 functions.

Treatment of lethally irradiated mice with a short course of high-dose interleukin (IL)-2 markedly inhibits acute and chronic graft-versus-host disease (GVHD), while preserving a graft-versus-leukemia (GVL) effect of allogeneic T-cells. We recently demonstrated that this GVL effect, observed with the EL4 leukemia/lymphoma in the A/J-->B10 strain combination, was mediated by CD8+ A/J T-cells in a CD4-independent fashion. IL-2 inhibited only the activity of CD4+ cells, and not that of CD4-independent CD8+ T-cells in A/J spleen cell inocula. This inhibition of CD4 function was sufficient to markedly inhibit GVHD, thus explaining the dissociation of GVHD and GVL in IL-2-treated mice. We have now performed studies to determine the capacity of IL-2 to inhibit GVHD induced across a variety of different histocompatibility barriers. IL-2 significantly delayed GVHD mortality in three of four additional fully major histocompatibility complex (MHC) plus minor-disparate strain combinations when CD4+ T-cells were given. Numbers of CD8+ T-cells comparable to those that might contaminate human marrow demonstrated a relatively poor capacity to produce acute GVHD when given without CD4+ cells in all of three additional strain combinations evaluated. In one of these strain combinations (B10-->BALB/c), IL-2 protected against acute but not chronic GVHD mortality when CD4+ cells were given with or without CD8+ cells. In one fully allogenic strain combination, B10-->A/J, IL-2 did not inhibit the GVHD produced by CD4+ cells given with or without CD8+ cells. IL-2 was unable to inhibit CD8-mediated GVHD in strain combinations differing at isolated class I MHC loci. In a strain combination differing only at multiple minor histocompatibility antigen (HA) loci, B10-->C3H.SW, GVHD was largely CD8-dependent, but IL-2 did not inhibit the small CD4-mediated component of GVHD. Together, these results suggest that IL-2 inhibits a restricted subset of CD4 cells or functions, and that the type of CD4 activities mediating GVHD is determined by the particular histoincompatibilities between donor and host.

Animals↗
PubMed1994

Childhood bacterial meningitis beyond the neonatal period in southern Nigeria: changes in organisms/antibiotic susceptibility.

Of 253 culture proven cases of bacterial meningitis in infants aged over a month and children up to one year old in Benin City, Nigeria, from 1985-1990, 49.8% were due to N. meningitidis, 21.4% S. pneumoniae, 15.4% H. influenzae and 13.4% other organisms, including S. aureus and enterobacteriaceae. Compared to the period 1974-1984 in Southern Nigeria, N. meningitidis has replaced S. pneumoniae as the commonest organism. N. meningitidis was relatively infrequent below two years of age while H. influenzae was rare after five years. Approximately half of isolates of S. aureus and enterobacteriaceae were in infants aged six months or less. The proportions of sensitive strains of three common organisms to three commonly used drugs were chloramphenicol (95.3%) > ampicillin (83.9%) > penicillin (67.6%). Resistance to penicillin has increased while simultaneous resistance to ampicillin and chloramphenicol has emerged as a new problem among the three common bacteria. It is concluded that although the combination of ampicillin and chloramphenicol is still reasonable for initial "blind" therapy of meningitis, the emergence of multiple drug resistance suggests the need for consideration of a revision of current practice. The third generation cephalosporins are suggested as a suitable alternative.

Age Factors↗
PubMed1994

Tolerance to discordant xenografts. I. Sharing of human natural antibody determinants on miniature swine bone marrow cells and endothelial cells.

Xenotransplantation could potentially overcome the organ shortage that currently limits the field of transplantation. Because of their breeding characteristics as well as their size and physiologic similarities to humans, we have chosen miniature swine as possible xenograft donors, and are currently attempting to develop a means of using mixed xenogeneic chimerism as an approach to tolerance induction in swine-to-primate species combinations. One major barrier to organ grafting from pig to man is the presence in human serum of preformed natural antibodies (NAb) reacting with antigens expressed on porcine endothelial cells and causing hyperacute rejection. Previous experiments performed in our laboratory have shown that both humoral and cellular tolerance can be induced in a concordant xenogeneic species combination (rat-->mouse) using donor bone marrow infusion following conditioning with a nonmyeloablative regimen. Induction of chimerism in these animals was associated with a marked reduction in the level of IgM natural antibodies that recognize rat bone marrow cells. A similar approach could also lead to humoral and cellular tolerance induction in the swine-->human species combination, permitting transplantation of vascularized organs from the swine donor. To determine the potential of bone marrow transplantation to induce a state of "natural antibody tolerance," it was essential to determine whether or not all human NAb target antigens expressed on swine EC are also expressed on cells derived from swine bone marrow. We have addressed this question by evaluating the ability of various swine bone marrow-derived cells to absorb human IgM and IgG NAb that bind to swine EC. Our results demonstrate that swine bone marrow cells and their progeny can absorb almost all IgM NAb that bind to swine EC, as detected by flow cytometric and ELISA assays. Specificity of absorption was demonstrated, as total serum IgM levels declined only minimally after absorption on swine BMC and to an extent comparable to that observed following absorption with human cells, which did not deplete swine EC-binding NAb. Human IgG binding to swine EC was also completely absorbed by swine BMC. These results suggest that a state of "NAb tolerance" could be induced by successful swine marrow engraftment in man. Furthermore, swine PBL, platelets, and EC were able to absorb most IgM NAb that bound to swine BMC, suggesting that absorption using antigen from any of these tissues might facilitate marrow engraftment, and hence tolerance induction, in this species combination.

Animals↗
PubMed1993

Hematopoietic cells and radioresistant host elements influence natural killer cell differentiation.

Radioresistant host elements mediate positive selection of developing thymocytes, whereas bone marrow-derived cells induce clonal deletion of T cells with receptors that are strongly autoreactive. In contrast to T cell development, little is known about the elements governing the natural killer (NK) cell repertoire, which, similar to the T cell repertoire, differs between individuals bearing different major histocompatibility complex (MHC) phenotypes. We have used murine bone marrow transplantation models to analyze the influence of donor and host MHC on an NK cell subset. We examined the expression of Ly-49, which is strongly expressed on a subpopulation of NK cells of H-2b mice, but not by NK cells of H-2a mice, probably because of a negative effect induced by the interaction of Ly-49 with Dd. To evaluate the effect of hematopoietic cell H-2a expression on Ly-49 expression of H-2b NK cells, we prepared mixed allogeneic chimeras by administering T cell-depleted allogeneic (B10.A, H-2a) and host-type (B10, H-2b) marrow to lethally irradiated B10 mice, or by administering B10. A marrow to B10 recipients conditioned by a nonmyeloablative regimen. Expression of H-2a on bone marrow-derived cells was sufficient to downregulate Ly-49 expression on both H-2a and H-2b NK cells. This downregulation was thymus independent. To examine the effect of H-2a expressed only on radioresistant host elements, we prepared fully allogeneic chimeras by administering B10 bone marrow to lethally irradiated B10.A recipients. B10 NK cells of these fully allogeneic chimeras also showed downregulation of Ly-49 expression. The lower level of H-2a expressed on H-2b x H-2a F1 cells induced more marked downregulation of Ly-49 expression on B10 NK cells when presented on donor marrow in mixed chimeras than when expressed only on radioresistant host cells. Our studies show that differentiation of NK cells is determined by interactions with MHC molecules expressed on bone marrow-derived cells and, to a lesser extent, by MHC antigens expressed on radioresistant host elements.

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