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M Sykes

Publications and source records attributed to M Sykes.

At least 145 records · Page 8Linked to original sources
PubMed1993

IL-2 reduces graft-versus-host disease and preserves a graft-versus-leukemia effect by selectively inhibiting CD4+ T cell activity.

We have recently demonstrated, in a fully MHC-mismatched murine bone marrow transplantation model, that administration of a short course of high dose IL-2 markedly diminishes graft-vs-host disease (GVHD) without compromising alloengraftment or the graft-vs-leukemia (GVL) effect of allogeneic T cells. We have now evaluated the mechanism of the dissociation of GVL and GVHD observed in this model. We demonstrate that CD4+ T cells were required to produce severe, acute GVHD in the fully MHC-mismatched plus minor histocompatibility Ag-mismatched A/J-->B10 strain combination. The GVHD-producing activity of A/J CD4+ T cells administered without CD8+ T cells was inhibited by IL-2 treatment. In contrast, CD8+ T cells alone mediated the GVL effect observed in the EL4 leukemia/lymphoma model, and CD4+ cells did not contribute to this effect. This CD8-mediated GVL activity was not inhibited by IL-2 treatment. Because naive A/J CD8+ T cells administered without CD4+ T cells did not produce acute GVHD, we were unable to evaluate the effect of IL-2 in this model. However, when A/J donors were presensitized with B10 skin grafts, CD4-depleted A/J spleen cells were capable of causing acute GVHD in B10 recipients. This CD8-mediated GVHD was not inhibited by treatment with IL-2. However, IL-2 did partially inhibit the GVHD produced by nondepleted presensitized A/J spleen cells, probably due to selective inhibition of the function of presensitized A/J CD4+ T cells. The dissociation of GVHD and GVL against the EL4 leukemia/lymphoma in IL-2-treated mice can therefore be explained by selective inhibition by IL-2 of CD4 activity.

Animals↗
PubMed1993

Novel approaches to the control of graft versus host disease.

Graft versus host disease (GVHD) remains the major obstacle to the application of bone marrow transplantation across HLA barriers. Recent advances in our understanding of GVHD pathophysiology have resulted in the evaluation in animal models and in clinical trials of some novel approaches to avoiding and treating GVHD. Continued advances in our knowledge are likely to result in the clinical application of biological therapies to maximize graft versus leukemia effects and alloengraftment, while avoiding GVHD.

Animals↗
PubMed1993

Specific prolongation of skin graft survival following retroviral transduction of bone marrow with an allogeneic major histocompatibility complex gene.

Engrafted allogeneic hematopoietic cells have a unique capacity to induce a state of donor-specific transplantation tolerance across major histocompatibility complex barriers. This state allows permanent acceptance of donor-type organ grafts, with otherwise normal immunocompetence. We hypothesized that introduction of allogeneic MHC genes into autologous bone marrow which is then returned to recipient mice might similarly induce specific tolerance to products of the introduced MHC genes, without the risk of graft-vs-host disease. We demonstrate here that the introduction of MHC class I Kb cDNA by retrovirus-mediated gene transfer into B10.AKM (Kk) hematopoietic cells confers specific hyporesponsiveness to allogeneic skin grafts expressing Kb.

Amino Acid Sequence↗
PubMed1992

Mechanism of protection from graft-versus-host disease mortality by IL-2. III. Early reductions in donor T cell subsets and expansion of a CD3+CD4-CD8- cell population.

Reducing the graft-vs-host disease (GVHD)-promoting capacity of allogeneic T cells while maintaining alloengraftment and graft-vs-leukemia effects remains an important but elusive goal in clinical bone marrow transplantation (BMT). We have recently demonstrated that a short course of high dose IL-2 administered at the time of BMT has a powerful protective effect against GVHD mortality in mice. This short course of IL-2 is able to protect mice from both acute and chronic GVHD without sacrificing alloengraftment or graft-vs-leukemia effects of allogeneic T cells. Because the early administration of IL-2 seems to be crucial for this effect, we have studied the early lymphoid repopulation events after lethal irradiation and allogeneic BMT. These studies show that there are consistent delays in splenic repopulation by allogeneic cells after BMT in IL-2-treated animals compared with their untreated cohorts. Even greater percent reductions were seen in donor splenic T cell populations in the first few days after BMT in IL-2-treated animals. Splenic cells with the CD3+CD4-CD8- phenotype were increased in IL-2 treated animals at days 3 and 4 after BMT. This phenotype resembles that of bone marrow-derived cells which have been previously shown to inhibit GVHD, suggesting a possible mechanism for the protective effect of IL-2.

Animals↗
PubMed1992

In vitro and in vivo effects of recombinant human interleukin-2 in naive miniature swine.

Recent data in mice have shown that early administration of recombinant human interleukin-2 (rIL-2) provides significant protection from lethal graft-versus-host disease. Because of the potential clinical importance of these findings, it will be important to assess the effectiveness of this therapy in a large animal preclinical bone marrow transplantation model. We report here our initial studies of the in vitro and in vivo effects of rIL-2 in miniature swine. In vitro 4-day cultures of pig peripheral blood lymphocytes (PBL) in complete medium containing rIL-2 at 1,000 U/ml resulted in optimal proliferation and generation of lymphokine-activated killer (LAK) cells. A pig-mouse hybridoma cell line was found to be highly sensitive as a LAK cell target. Two naive pigs received 20,000 U/kg and 2 pigs received 100,000 U/kg of rIL-2 intravenously twice a day for 4 days. No clinical symptoms were seen during or after administration at the lower dose while both high dose-treated animals showed generalized erythema from days 2 to 4, and one showed mild diarrhea during this period. The disappearance of IL-2 activity from the serum showed two components: (1) an initial fast component with a half-time of approximately 10 min and (2) a slow component with a half-time of approximately 60 min. LAK cell precursors disappeared from the peripheral circulation by 6 min after rIL-2 administration and began to recover by 6 h in the low dose recipients and only after 12 h in the high dose recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The mechanism of IL-2-mediated protection against GVHD in mice. II. Protection occurs independently of NK/LAK cells.

We have recently demonstrated that high-dose IL-2, when begun on the day of bone marrow transplantation, has a potent protective effect against graft-vs.-host disease mortality, especially when coadministered with T cell-depleted syngeneic bone marrow cells. Because several groups of investigators have demonstrated that lymphokine-activated killer cells can mediate GVHD protection, we hypothesized that the mechanism of protection by IL-2 administration might involve the in vivo activation of natural killer and/or LAK cells. In order to test this hypothesis, we evaluated the effect of IL-2 administration on the number of NK1+ cells and on NK-mediated cytotoxic activity in recipients of GVHD-producing inocula. Furthermore, we evaluated the effects on IL-2-induced GVHD protection of depleting NK cells and LAK precursor cells in vivo with mAb against NK1.1 or antiserum against asialo GM1. The results demonstrate that: (1) The number of NK1+ cells is not increased in spleens of IL-2-treated compared with control recipients of GVHD-producing inocula; (2) NK activity is not increased in IL-2-treated compared with control recipients of GVHD-producing inocula during or immediately following the period of IL-2 administration; (3) depletion of NK cells and LAK precursors from the donor and host influenced the time course of GVHD-related mortality in a complex fashion; and (4) IL-2-induced GVHD protection is largely independent of the activity of an NK or LAK cell population of donor or host origin. IL-2-induced GVHD protection therefore reflects primarily the activity of non-LAK protective cell populations, or it may be a direct inhibitory effect on responding donor cell populations as they encounter host antigen.

Animals↗
PubMed1992

Humoral tolerance in xenogeneic BMT recipients conditioned by a nonmyeloablative regimen.

We have recently demonstrated that mixed xenogeneic chimerism and donor-specific tolerance can be produced across a species barrier using a nonmyeloablative conditioning regimen (1). This regimen involves pretreatment of B10 mice with mAbs against CD4+, CD8+, Thy1+, and NK1+ cells, followed by a low dose (3 Gy) of whole-body irradiation and a higher dose (7 Gy) of local irradiation to the thymus and administration of T cell-depleted (TCD) F344 strain rat BMC. Although initial mixed chimerism and de novo maturation of donor rat T cells can be demonstrated in such animals, chimerism is gradually lost, and is no longer detectable by 6 months following BMT (1). When rat skin was grafted onto such animals 4 months following BMT, however, donor-specific skin graft survival was markedly prolonged, while non-donor type rat skin grafts were rapidly rejected (1). These results suggested that a state of donor-specific T cell tolerance existed, and that loss of chimerism was not due to a T cell-mediated immune mechanism. In order to evaluate the possibility that a humoral mechanism might mediate delayed loss of xenogeneic bone marrow grafts, we have now examined sera at various times for the presence of antibody against donor cells. Groups of animals not receiving the complete tolerizing mAb pretreatment regimen produced antidonor lymphocytotoxic antibody in response to BMT and skin grafting. Flow cytometric studies demonstrated high levels of IgM and of IgG of all subclasses against rat BMC and spleen cells in these control mice immunized by BMT. In contrast, such antibodies were not detectable in sera from animals receiving BMT following pretreatment with the tolerance-inducing mAb regimen. Furthermore, the tolerant animals did not develop cytotoxic antibodies or high levels of IgM or IgG against donor BMC after loss of hematopoietic chimerism. Donor-type skin grafts were eventually rejected, but rejection of these and repeat skin grafts did not lead to a cytotoxic antibody response. Low levels of rat BMC-binding IgM antibody were also detected in sera of tolerant mice, but the intensity of staining of rat BMC was lower than that of control animals receiving conditioning without BMT. These results suggest that a state of tolerance exists among cells responsible for T cell-dependent IgG antibody subclasses and natural IgM antibodies in animals receiving BMT following this nonmyeloablative conditioning regimen.

Animals↗
PubMed1992

Mixed allogeneic chimeras prepared by a non-myeloablative regimen: requirement for chimerism to maintain tolerance.

We have recently described a non-myeloablative conditioning regimen permitting engraftment of allogeneic bone marrow in mice which involves administration of anti-CD4 (GK1.5) plus anti-CD8 (2.43) monoclonal antibodies in vivo, 3 Gy whole body irradiation, plus 7 Gy thymic irradiation. B10 (H-2b) mice prepared by this regimen and infused with unmanipulated B10.D2 (H-2d) bone marrow develop permanent mixed lymphohematopoietic chimerism and specific tolerance to donor skin grafts. We now demonstrate that mixed chimerism persists longer than 170 days in the lymphoid tissues including spleen, thymus and bone marrow of such animals, and that equivalent levels of donor chimerism are observed in both T and B cell compartments. In addition stable mixed chimeras were found to be unresponsive to host (B10) and donor (B10.D2) stimulator cells in mixed lymphocyte reaction and in cell mediated lympholysis assays, while responses to a third party (B10.BR, H-2k) were intact. Persistent chimerism was found to be necessary for the maintenance of skin graft tolerance in these animals, since in vivo depletion of donor cells by treatment with an anti-H-2d (34-2-12) monoclonal antibody resulted in the subsequent rejection of donor skin grafts. These studies demonstrate that mixed allogeneic chimeras produced using this regimen are specifically tolerant to donor in vitro and in vivo, and that persistence of donor chimerism is critical for the maintenance of tolerance.

Animals↗
PubMed1992

Alloengraftment in IL-2-treated mice.

Despite major advances, graft-versus-host disease (GVHD) remains a major obstacle to clinical bone marrow transplantation. Prophylaxis by T cell depletion is associated with increased rates of engraftment failure and leukemic relapse. Treatment with high-dose IL-2 can markedly protect lethally irradiated mice from GVHD-related mortality, especially when T cell-depleted (TCD) syngeneic bone marrow cells (BMC) are co-administered. In these IL-2-protected animals, allogeneic reconstitution is observed, and a graft-versus-leukemia effect of allogeneic T cells is preserved. To determine whether IL-2 might increase alloresistance under conditions in which alloengraftment is more difficult to achieve, we have now evaluated the possible effect of IL-2 on: (1) competitive repopulation of lethally irradiated mice by mixtures of TCD allogeneic and TCD syngeneic BMC; (2) radiation protection by TCD allogeneic BMC; (3) timing of hematologic recovery; and (4) allogeneic engraftment in sublethally irradiated recipients. The results show that IL-2 has only a limited and strain-restricted effect on alloengraftment. This effect may reflect activation of alloresistant host natural killer cells, a cell population which is not essential for the protective effect of IL-2 against GVHD.

Animals↗
PubMed1991

Natural antibodies can inhibit bone marrow engraftment in the rat----mouse species combination.

Specific tolerance can be induced in animals by transplanting hemopoietic cells across concordant species barriers. Despite the fact that the rat-mouse species combination is considered concordant, we have recently demonstrated that normal murine serum contains natural antibodies (nAb), predominantly of the IgM and IgG3 subclasses, with markedly greater binding to rat bone marrow cells (BMC) than to rat splenocytes or thymocytes. Since much greater numbers of rat BMC than of allogeneic murine BMC are required to achieve engraftment in mice, we considered the possibility that these nAbs might be responsible, and that the increased numbers of BMC might be required to absorb these nAb. To evaluate the effect of these nAb on engraftment of rat BMC in mice, we have now performed adoptive transfer studies using T and B cell-deficient severe combined immunodeficiency disease (SCID) mice as recipients. Administration of as few as 5 x 10(5) T cell-depleted rat BMC led to induction of stable xenochimerism in SCID mice conditioned with 4-Gy whole body irradiation. Rat T cells developed after a delay of several weeks, and conferred the ability to reject non-donor-type rat skin grafts, whereas donor-type grafts were accepted. Adoptive transfer of 4 ml of normal BALB/c serum led to a marked reduction in the level of rat chimerism in SCID recipients of 2 x 10(6) F344 BMC. The ability of sera to inhibit engraftment of rat BMC correlated with their cytotoxic nAb content, and the inhibitory effect of highly cytotoxic sera could be overcome by administration of large numbers of rat BMC. Thus, normal mouse serum has a limited ability to hinder engraftment of rat BMC, and this degree of resistance can be overcome by adsorption when large numbers of BMC are administered. Eliminating nAb from serum may be more difficult in discordant species combinations in recipients with functional B cells, but may likewise permit the use of BMT as a means of inducing transplantation tolerance.

Animals↗
PubMed1991

Natural antibodies against bone marrow cells of a concordant xenogeneic species.

Hyperacute rejection does not occur when vascularized organs are transplanted between rat and mouse, and this species combination is considered to be concordant. Since hyperacute rejection is believed to reflect the presence of pre-existing antibodies (usually of the IgM class), and lymphocytotoxic antibodies against rat cells have not been detected in normal mouse sera, it has previously been concluded that mouse anti-rat natural antibody (NAb) does not exist. However, studies have not been reported in which rat bone marrow cells (BMC) were used as targets for evaluation of normal mouse sera. Because previous work from our and other laboratories has shown that bone marrow chimerism in the rat into mouse species combination can be achieved only by transplanting large numbers of rat BMC, we have evaluated normal mouse sera for the presence of NAb against rat BMC that might explain these in vivo results. Fisher 344 rat BMC and spleen cells were incubated with serum from nonimmunized mice, then stained with fluoresceinated rat anti-mouse subclass-specific secondary reagents and analyzed using flow cytometry. NAb of the IgM and IgG3 classes were found that bound strongly to rat BMC but showed weak or absent binding to spleen cells. A low level of IgG2b binding was observed to both BMC and spleen cells. Cytotoxic activity was detected against rat BMC but not against spleen cells. The environment in which the animals were maintained played a significant role in determining the level of cytotoxic NAb in normal mouse sera. Our results are consistent with the possibility that bone marrow-specific NAb play a role in resisting engraftment of BMC across this species barrier.

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