Qi-Wei Zhang

Induction of Permanent Mixed Chimerism and Skin Allograft Tolerance Across Fully MHC-Mismatched Barriers by the Additional Myelosuppressive Treatments in Mice Primed with Allogeneic Spleen Cells Followed by Cyclophosphamide

A pure method of drug (cyclophosphamide plus busulfan)-induced skin allograft tolerance in mice that can regularly overcome fully H-2-mismatched barriers in mice has been established. The components of the method are i.v. administration of 1 × 108 allogeneic spleen cells on day 0, i.p. injection of 200 mg/kg CP and 25 mg/kg busulfan on day 2, and i.v. injection of T cell-depleted 1 × 107 bone marrow cells from the same donor on day 3. Recipient B10 (H-2b; IE−) mice prepared with this conditioning developed donor-specific tolerance, and long-lasting survival of skin allografts was shown in almost of the recipient mice. In the tolerant B10 mice prepared with new conditioning, stable multilineage mixed chimerism was observed permanently, and IE-reactive Vβ11+ T cells were reduced in periphery as seen in untreated B10.D2 (H-2d; IE+) mice. The specific tolerant state was confirmed by the specific abrogation against donor Ag in the assays of CTL activity and MLR and donor-specific acceptance in the second skin grafting. These results demonstrated that the limitation of standard protocol of cyclophosphamide-induced tolerance, which have been reported by us since 1984, can be overcome by the additional treatments with the myelosuppressive drug busulfan, followed by 1 × 107 T cell-depleted bone marrow cells. To our knowledge, this is the first report to induce allograft tolerance with a short course of the Ag plus immunosuppressive drug treatment without any kind of mAbs (pure drug-induced tolerance).

Improved technique of heterotopic cervical heart transplantation in mice

BACKGROUND The method for mouse vascularized heart transplantation have been described using suture and cuff techniques. Technical problems have limited its widespread use. Here, we describe our method of modified cervical heterotopic transplantation with the cuff technique. METHODS By using a smaller Teflon cuff (external diameter 0.6 mm, internal diameter 0.4 mm) and superfine-tip forceps, it became possible to directly pull the edge of the carotid artery and evert the proximal end of the artery over the cuff. Similarly, the external jugular vein could be easily everted over a 22-gauge cuff with this direct pulling method. RESULTS By these modifications, the operation time was reduced. It usually takes 20 min for the donor harvest, 15 min for preparation of the cervical vessels, and 15 min for anastomosis. All procedures from the donor harvest through skin closure of the recipient mice can be completed within 1 hr, and ischemic time is within 25-40 min. CONCLUSIONS This method can be used to investigate cyclophosphamide-induced tolerance and mechanisms of reperfusion injury.

Fractionated dosing of cyclophosphamide for establishing long-lasting skin allograft survival, stable mixed chimerism, and intrathymic clonal deletion in mice primed with allogeneic spleen cells

BACKGROUND Injection of allo-spleen cells (SC) followed by a single dose of cyclophosphamide (CP) can induce tolerance of tumor and/or skin allografts in mice. To minimize the damage caused by CP, fractionation of CP that can establish long-lasting skin graft survival, stable mixed chimerism, and intrathymic clonal deletion in the host was investigated in the present study. METHODS Allo-SC (10(8)) were given intravenously on day 0. CP at 200 mg/kg was given intraperitoneally on day 2 in a single dose (CP 200x1 group). CP at 100, 66, 50, 40, and 33 mg/kg was given daily from day 1 through days 2, 3, 4, 5 and 6, respectively, in the fractionated doses (CP 100x2, 66x3, 50x4, 40x5, and 33x6 groups; total dose=200 mg/kg). Allografting was performed on day 14. RESULTS In a fully allogeneic combination of C57BL/6 (H2b)-->AKR (H2k, Mls-1a), an EL-4 tumor (H2b) was specifically accepted to kill the AKR mice in all of the SC+CP 200x1, 100x2, 66x3, 50x4, 40x5, and 33x6 groups (n=6), but C57BL/6 skin graft survival was not prolonged in any of the tumor-tolerant groups. In an H2-identical combination of AKR-->C3H (H2k, Mls-1b), AKR skin graft survival was prolonged remarkably (80-90 days) in the SC+CP 200x1, 100x2, and 66x3 groups (n=5-11), but was prolonged moderately (20-60 days) in the SC+CP 50x4 and 40x5 groups. In both of the SC+CP 200x1 and 66x3 groups in the AKR-->C3H combination, mixed chimerism was maintained for as long as 100 days after tolerance induction in both the spleen and thymus, associated with intrathymic clonal deletion of Vbeta6+ T cells. The decreases in leukocyte count, hemoglobin level, spleen weight, SC count, and body weight were significantly smaller in the SC+CP 66x3 group than in the SC+CP 200x1 group. CONCLUSIONS Fractionated CP is effective in ameliorating the compromised state induced by a single dose of CP. To induce a long-lasting skin allograft survival associated with stable mixed chimerism and intrathymic clonal deletion in an H2-identical combination, 200 mg/kg of CP can be divided into three or fewer fractions.

A technique of cervical aortic graft transplantation in mice.

A new method of mouse aortic graft transplantation into carotid artery was developed with cuff technique. By harvesting the descending aorta of the donor using a small Teflon cuff (external diameter 0.6 mm, internal diameter 0.4 mm) and super fine-tip forceps, and modifying the method of mouse heterotopic heart transplantation with cuff technique, donor descending aortic allografts could be interposed in the common carotid artery of recipient mice. Histological analysis demonstrated neither evidence of tissue damage nor intimal thickening in isograft implanted over 100 days. We strongly recommend that this new model of aortic transplantation in mice is a simple and useful technique for vascular transplantation research.

Heart allograft tolerance without development of posttransplant cardiac allograft vasculopathy in chimerism-based, drug-induced tolerance.

BACKGROUND Recently, we have described a drug (cyclophosphamide [CP] plus busulfan [BU])-induced skin allograft tolerance in mice that can regularly overcome fully H-2-mismatched barriers. Using this method, we have investigated whether or not this regimen can prolong the survival of heart allografts and inhibit the development of posttransplant cardiac allograft vasculopathy (CAV). METHODS The components of the method are intravenous administration of 1 x 108 allogeneic spleen cells on day 0, intraperitoneal injection of 200 mg/kg of CP and 30 mg/kg of BU on day 2, and intravenous injection of T cell-depleted 1 x 107 allogeneic bone marrow cells from the same strain of mice on day 3. Heart grafting was performed on day 28. Chimerism in peripheral blood was followed by flow cytometric analysis, and histological analysis was performed at various times after grafting. RESULTS In a fully major histocompatability complex (MHC)-mismatched combination of B10.D2 (H-2d, IE+)-->B10 (H-2b, IE-), stable, multilineage-mixed chimerism was observed permanently. B10.D2 heart grafts were accepted permanently in a donor-specific manner, and posttransplant CAV did not develop. CONCLUSIONS These results demonstrated that the drug-induced tolerance recently established by us can regularly induce a long-lasting heart allograft tolerance without development of CAV.

Mixed chimerism, heart, and skin allograft tolerance in cyclophosphamide-induced tolerance.

We elucidated the possible role of chimerism in skin and heart allograft tolerance using cyclophosphamide (CP)-induced tolerance. When C3H (H-2k; Thy1.2, Mls-1b) mice were i.v. primed with 1x10(8) spleen cells (SC) from H-2 matched AKR (H-2k; Thy1.1, Mls-1a) mice and then treated i.p. with 200 mg/kg of CP, the survivals of both AKR skin grafts and heart grafts (HG) were permanently prolonged in a tolerogen-specific fashion. After this treatment, a minimal degree of mixed chimerism, the clonal destruction of Mls-1a-reactive CD4+Vbeta6+ T cells in the periphery, and the clonal deletion of Vbeta6+ thymocytes were all observed. When AKR SC and 100 mg/kg CP were used for conditioning, the AKR HG were permanently accepted, but the survival of the AKR skin grafts was only mildly prolonged. The clonal destruction of CD4+Vbeta6+ T cells in the periphery and the intrathymic clonal deletion of Vbeta6+ thymocytes were induced in both the SC and the 100 mg/kg CP-treated C3H mice. A minimal degree of mixed chimerism was detectable at 4 and 12 weeks after AKR SC and 100 mg/kg CP treatment, and still did not disappear at 40 weeks. The degree of mixed chimerism induced with SC and 100 mg/kg CP was significantly lower than that with SC and 200 mg/kg CP during the observation. No posttransplant cardiac allograft vasculopathy (CAV) was observed to develop, while both the Th1 type (interferon-gamma) and Th2 type (interleukin-4 and -10) cytokine expressions decreased in the AKR HG of the tolerant C3H mice treated with both AKR SC plus 200 mg/kg CP, and AKR SC plus 100 mg/kg CP. A second set of skin grafts from donor AKR mice survived for more than 100 days in a tolerogen-specific fashion in all C3H mice treated with AKR SC and 200 mg/kg CP and also accepted the AKR HG for over 200 days, while 80% of the C3H mice treated with AKR SC and 100 mg/kg CP and accepted the AKR HG for more than 200 days. These results strongly suggested the following conclusions: 1) the degree of chimerism can strongly influence the induction of skin and heart allograft tolerance, 2) posttransplant CAV does not develop in the donor HG maintained by chimerism-based CP-induced tolerance, 3) the mRNA expression of both Th1 and Th2 type cytokine decreased in the donor HG maintained by chimerism-based CP-induced tolerance, and 4) the induction of skin allograft tolerance is more difficult than the prevention of posttransplant CAV.

Inability of cyclophosphamide-induced tolerance to permit engraftment of pluripotent stem cells contained in a moderate number of syngeneic bone marrow cells.

We have previously described cyclophosphamide (CP)-induced tolerance that comprises an intravenous (i.v.) injection of 1 x 10(8) allogeneic spleen cells (SC) followed, 2 days later, by an intraperitoneal (i.p.) administration of 200 mg/kg of CP. By using this method, we were able to readily induce both long-lasting mixed chimerism and skin allograft tolerance in most of H-2 matched combinations, but not in H-2 mismatched combinations. In the present study, we have investigated whether the treatment with SC followed by 200 mg/kg CP can permit engraftment of syngeneic pluripotent hematopoietic stem cells (HSC), and whether CP itself can permit the HSC engraftment. Recipient B6 (H-2b; Ly-5.2) mice received 1 x 10(7), 5 x 10(7) or 1 x 10(8) SC from syngeneic B6.Ly-5.1 (H-2b; Ly-5.1) mice and administered 2 day later 200 mg/kg CP. Using anti-Ly-5.1 and Ly-5.2 mAbs and a flow cytometry, the origins of lymphoid and myeloid cells injecting the recipients were observed over time. Chimerism was at least initially detectable in all groups treated with SC alone (without 200 mg/kg CP), but became undetectable by 32 weeks after the treatment with SC alone. In recipient B6 mice treated with B6.Ly-5.1 SC and 200 mg/kg CP, on the other hand, lymphoid-chimerism was detectable at 32 weeks in a transferred cell dose-dependent manner, but granulocyte-chimerism indicating pluripotent HSC engraftment disappeared earlier than 32 weeks after the treatment. In order to further evaluate the effect of CP itself on HSC engraftment, recipient B6 mice were given various doses of CP (50-400 mg/kg) and were injected with T cell-depleted 1 x 10(7) BMC from B6.Ly-5.1 mice. Multilineage mixed chimerism over 32 weeks was induced in only one of 11 B6 mice treated with 400 mg/kg CP followed by B6.Ly-5.1 BMC, although lymphoid chimerism was induced temporarily in recipient B6 mice treated with 200 mg/kg CP followed by B6.Ly-5.1 BMC and persistently in most of recipient B6 mice treated with 400 mg/kg CP followed by B6.Ly-5.1 BMC.

The regulatory functions of Ly‐49A, Ly‐49D and Ly‐49G2 on NK cells in the recognition and rejection of the alloantigen in vivo*

Ly‐49A is an inhibitory receptor that binds H‐2Dd and H‐2Dk. The downregulation of Ly‐49A is thought to mediate NK self tolerance in vivo. In this study, we analyzed the regulation of Ly‐49A, D and G2 on NK cells in an in vivo rejection model. After injection with 1 × 108 B10.D2 spleen cells (SC) into B 10 mice, we found Ly‐49A downregulated within 3 h on NK cells of B10 mice, whereas expressions of Ly‐49D and G2 were augmented. To investigate effects of different expression patterns of Ly‐49 receptors on NK cells, Ly‐49A, D or G2‐depleted B10 mice were inoculated with B10.D2 SC. NK cells from SC of Ly‐49A‐depleted and B10.D2 SC‐injected B10 mice showed enhanced cytotoxicity to Dd‐positive targets in vitro. Furthermore, reduced numbers of B10.D2 SC were observed in Ly‐49A or G2‐depleted B10 mice, whereas increased numbers of B10.D2 SC were observed in Ly‐49D‐depleted B10 mice after inoculation with B10.D2 SC in vivo. These findings indicated that the downregulation of Ly‐49A and the augmentation of Ly‐49D expression may mediate NK cells to recognize and kill Dd antigen efficiently. In conclusion, each Ly‐49 isoform may play independent roles in the regulation of activation or inhibition on NK cells.

Absent mRNA accumulation of Th1 or Th2 cytokines in heart allografts with chimerism-based drug-induced tolerance.

PurposeWe recently described using cyclophosphamide (CP) plus busulfan (BU) to create drug-induced skin and heart allograft tolerance capable of regularly overcoming fully H-2 mismatched barriers in mice. The present study investigates the intragraft mRNA expressions of Th1 and Th2 cytokines.MethodsThis method consists of the intravenous (i.v.) injection of 1 × 108 allogeneic spleen cells on day 0, the intraperitoneal injection of 200 mg/kg CP and 30 mg/kg BU on day 2, and the i.v. injection of 1 × 107 T cell-depleted allogeneic bone marrow cells from the same strain of mice on day 3. Heart grafting (HG) was performed on day 28. Chimerism in the peripheral blood was monitored by flow cytometric (FCM) analysis. The frequency of certain Vβ families was determined by FCM to assess deletion of donor-reactive T cells. Th1 (interleukin [IL]-2, interferon [IFN]-γ) and Th2 (IL-4, IL-10) cytokine expression in the heart grafts was analyzed with reverse transcription–polymerase chain reaction.ResultsIn a fully MHC mismatched combination of B10.D2 (H-2d, IE+) → B10 (H-2b, IE−), B10.D2 heart grafts were accepted permanently in a donor-specific manner, mixed chimerism was observed, and IE-reactive Vβ11+ T cells were specifically reduced in the periphery from the recipient B10 mice. In the donor B10.D2 heart grafts, there was no accumulation of Th1 (IL-2, IFN-γ) or Th2 (IL-4, IL-10) cytokines.ConclusionsThese results show that the drug-induced tolerance we established can regularly induce long-lasting heart allograft tolerance without intragraft mRNA accumulation of Th1 or Th2.

Human Skin Xenograft Rejection in CD45 Exon-6 Knockout Mice: The Implication of Involvement of a Direct Pathway

Abstract The results of previous studies indicate that only CD4+ T cells generated via the indirect pathway play an essential role in causing discordant skin xenograft rejection. The present study was conducted in an attempt to clarify further the roles of effector T cells generated via direct pathways on discordant xenograft rejection using CD45 exon-6 knockout (CD45−/−; C57BL/6 (B6): H-2b) mice. It has been strongly suggested that CD45 exon-6 knockout mice have profound impairment in T-cell functions via an indirect pathway. When human skin was grafted onto untreated normal C57BL/6 (B6; H-2b) mice, rejection occurred within 12 days; however, in the CD45 exon-6 knockout mice, the grafts lasted for slightly longer as in fully allogeneic C3H (H-2k) skin rejection, with a mean survival time ± SD of 19.4 ± 1.5 days and median survival times of 19 days. The difference in survival periods between the human and C3H skin grafts in the CD45 knockout mice was not statistically significant. Both CD4+ and CD8+ T cells seemed activated in the spleens of these CD45 exon-6 knockout mice 10 days after the human skin grafting. These results suggest that effector T cells generated via a direct pathway can cause discordant skin xenograft rejection, and that CD45 exon-6 knockout mice can generate effector T cells via a direct pathway to reject discordant skin xenografts, similarly to fully allogeneic skin allografts.