Hisanori Mayumi

Drug-induced tolerance to allografts in mice. I. Difference between tumor and skin grafts.

When AKR mice were primed with viable C57BL/6(B6) spleen cells and treated with cyclophosphamide 1-3 days later, a profound tolerance to B6 tumor allografts was induced. The tolerant state was maintained completely for as long as 8 weeks. Although tumor allografts grew progressively even when inoculated after complete rejection of skin grafts, B6 skin grafts were rejected by tolerant mice. In mice tolerant of B6 tumors, production of cytotoxic antibody and cytotoxic activity was reduced profoundly, but the delayed-type hypersensitivity level decreased only slightly. We therefore presume that the decrease in cytotoxic activity may allow progressive growth of tumor allografts, but the maintenance of delayed-type hypersensitivity or a low level of cytotoxicity, or both, precludes acceptance of skin allografts.

Sequential mechanisms of cyclophosphamide-induced skin allograft tolerance including the intrathymic clonal deletion followed by late breakdown of the clonal deletion.

The cellular basis of the transplantation tolerance in a model system of BALB/c (Mls-1b) mice rendered cyclophosphamide (CP)-induced tolerant to DBA/2 (Mls-1a) skin allograft was investigated by assessing V beta 6+ T cells. From our results, three major mechanisms that are essential to the CP-induced skin allograft tolerance were sequentially elucidated. The first mechanism was destruction of donor-Ag-stimulated T cells in the periphery by CP treatment. The second mechanism was intrathymic clonal deletion of donor-reactive T cells, such as V beta 6+ T cells, correlating strongly with intrathymic mixed chimerism. The clonal deletion, however, was not always essential for the maintenance of the skin allografts, because DBA/2 skin survived even after the clonal deletion terminated and V beta 6+ T cells reappeared in the periphery of the recipient BALB/c mice. The third mechanism was generation of tolerogen-specific suppressor T cells, especially in the late stage of the tolerance. In contrast, the clonal anergy that is evidenced by the specific suppression of mixed lymphocyte reaction in the recipient BALB/c mice after injecting with DBA/2 spleen cells alone was not considered as a significant mechanism in prolonging skin allograft survival because such anergic mice showed accelerated rejection of the skin allografts. These results may suggest practical hierarchy of the mechanisms of CP-induced allograft tolerance.

DRUG-INDUCED TOLERANCE TO ALLOGRAFTS IN MICE: VI. TOLERANCE INDUCTION IN H-2-HAPLOTYPE-IDENTICAL STRAIN COMBINATIONS IN MICE

When C3H/HeN (C3H) mice were primed with viable AKR/J (AKR) spleen cells and treated with cyclophosphamide (CP) two days later, a profound tolerance to AKR skin grafts was induced. This tolerance was induced also in other combinations disparate only at minor histocompatibility (H) antigens (AKR-C3H and BALB/c[BALB]-DBA/2[DBA]). In C3H mice made tolerant to AKR, delayed foot-pad reaction (DFR), cytotoxic lymphocytes (CTL), and cytotoxic antibodies (CTAb) against AKR spleen cells were abrogated completely. Tolerance to AKR mice was also observed in C3H mice primed with viable AKR and C57BL/6 (B6) spleen cells and treated with CP, but tolerance to B6 was not induced because a cell population responsible for DFR and CTL against B6 H-2 antigens remained after tolerance induction. These results suggest that there is a lymphocyte population responsible for DFR and CTL against antigens allogeneic at both major and minor H that is less proliferative than the population responsible for DFR and CTL against minor H antigens.

Huge false aneurysm due to rupture of the right coronary artery in Behcet's syndrome

dine, procainamide, and disopyramide.6 Torsades de pointes was not observed in our patient, although it might be potentially manifested in the presence of significant flecainide-induced QT, prolongation. In our current controlled study of 14 patients with ventricular ectopy taking flecainide versus quinidine, four patients randomized to quinidine had clinical side efl’ects such as diarrhea, causing them to discontinue treatment. It appears that flecainide results in less frequency of similar side effects and possesses potent suppression (> 85 % ) of VPCs. While the single patient presented herein manifeste,d the unusual response of VT with flecainide, a number of studies including our own L* have shown no other or similar adverse effects. F’lecainide remains a promising new antiarrhythmic agent that warrants further clinical investigation.

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.

Drug-induced tolerance to allografts in mice. IX. Establishment of complete chimerism by allogeneic spleen cell transplantation from donors made tolerant to H-2-identical recipients.

Graft-versus-host reaction (GVH) after allogeneic spleen cell transplantation was completely suppressed in an H-2-matched murine combination (AKR/J Sea [H-2k] → lethally irradiated C3H/He Slc [H-2k]) by pretreatment of the donors with recipient spleen cell antigen plus cyclophosphamie (CP). Irradiated recipients receiving cells became chimeric. In contrast to the H-2 matched combination, lethal GVH reaction could not be prevented in an H-2-mismatched fully allogeneic combination (C57BL/6 Cr Slc [H-2b] → lethally irradiated C3H/He Slc [H-2k]) by pretretment of the donors. The results suggest that the effectors responsible for the GVH reaction were abrogated by pretreatment of the donors with allogeneic recipient spleen cells plus CP in the H-2-matched combination, but donor pretreatment failed to abrogate GVH reaction in the H-2-mismatched combination.

Drug-induced tolerance to allografts in mice. XII. The relationships between tolerance, chimerism, and graft-versus-host disease.

When AKR/J Sea (AKR, H-2k) mice were primed i.v. with 1×108 viable spleen cells from naive C3H/He Slc (C3H, H-2k) mice and treated i.p. with 200 mg/kg eyclophosphamide (CP) 2 days later, a minimal degree of mixed chimerism associated with tolerance to C3H skin was established without graft-versus-host disease (GVHD) and maintained for at least one month. When AKR mice were primed i.v. with 1×108 viable spleen cells from C3H mice preimmunized i.v. 7 days earlier with 5×107 viable AKR spleen cells, and treated with 200 mg/kg CP, chimerism became exclusive, but lethal GVHD occurred in the AKR mice. Moreover, most of normal AKR mice primed with the preimmunized C3H spleen cells without CP died of GVHD. In contrast, in a major histocompatibility complex (MHC)-incompatible combination of AKR (H-2k)-C57BL/6 Cr Slc (B6, H-2b), mixed chimerism, tolerance to skin allografts, and GVHD were not observed, whether or not the mice had been treated with naive or preimmunized B6 spleen cells with or without CP.

Use of Automatic Mode Change Between DDD and AAI to Facilitate Native Atrioventricular Conduction in Patients with Sick Sinus Syndrome or Transient Atrioventricular Block

The benefits of the automatic DDD (DDD/AMC) mode in the Chorus II pacemaker (Chorus 6234; Ela Medical Inc.), which automatically switches the modes between DDD and AAI to respect spontaneous AV conduction as much as possible in AAI while preserving safety pacing in DDD during paroxysmal AV block (AVB) only, remain unproven. This study examined the functions of the DDD/AMC mode in 12 patients with sick sinus syndrome (SSS; n = 10) or paroxysmal complete AVB (n = 2). A short‐term (24 hours) comparative study between simple DDD mode and the DDD/AMC mode was performed in 8 of the 12 patients, and a medium‐term (55.2 ± 54.6 days) follow‐up of the DDD/AMC mode was completed in all 12 patients. A comparative pair of 24‐hour surface Holter ECGs was obtained in 6 of the 8 patients in the short‐term study. Telemetry and built‐in Holter histograms were collected in the outpatient clinic in all 12 patients. Although the percentage atrial pacing of the telemetry increased from 59.2 ± 35.4 in DDD to 70.4 ± 31.8 in DDD/AMC (P < 0.009; n = 8), the percentage ventricular pacing decreased from 64.6 ± 37.7 in DDD to 36.2 ± 43.1 in DDD/AMC (P < 0.027) in the short‐term study. In particular, the reduction of percentage ventricular pacing to < 10% was observed in four patients with SSS not associated with ± first‐degree (1°) AVB on preoperative ECGs. Between the two modes a significant difference in arrhythmic events was not observed by the 24‐hour surface Holter ECGS taken from the six patients in the short‐term study. AAI‐DDD switching associated with automatic modulation of AV delay and AV hysteresis occurred in all patients in the medium‐term study. From the medium‐term study, the total AV delay (AV delay plus AV hysteresis) exceeded 300 ms in 6 of the 12 patients in DDD/AMC, and usually became longest during nighttime. From the short‐ or medium‐term study in the 12 patients, two patients preferred the DDD/AMC mode while one preferred the DDD mode. These results suggest that the DDD/AMC mode is useful, at least in SSS patients without ≥ 1° AVB, by reducing the percentage ventricular pacing.

Donor-specific prolongation of rat skin graft survival induced by rat-donor cells and cyclophosphamide under coadministration of monoclonal antibodies against T cell receptor alpha beta and natural killer cells in mice.

Because of the recent interest in human xenotransplantation, we investigated the possibility of inducing tolerance in a xenogeneic combination using cyclophosphamide (CP). Donor-specific prolongation of xenogeneic Fisher 344 (F344) rat skin graft survival for up to 60 days was induced in C57BL/6 (B6) mice by giving F344 bone marrow cells and spleen cells on day 0, CP on day 2, and monoclonal antibodies against murine TCR-alpha beta and NK1.1 on days--1 and 3. The inoculation of the xenogeneic cells brought accelerated repopulation of TCR-alpha beta+ T cells, even under the administration of anti-TCR-alpha beta mAb. The quick increase of the host TCR-alpha beta+ T cells caused by the xenogeneic cell injection was deeply suppressed by CP. Mixed lymphocyte reaction, CTL activity, and antibody production against donor F344 were profoundly suppressed for 50 days. Mixed xenogeneic chimerism was observed for 1 month after the inoculation of donor cells in the spleen and peripheral blood of the recipient B6 mice, but was never observed in the thymus. Moreover, when irradiated F344 cells were used in place of viable cells, chimerism was never detected and graft survival was only slightly prolonged. Clonal deletion of V beta 5- or V beta 11-bearing murine T cells was not observed on day 50 in the thymus or spleen of the recipient B6 mice. These results suggest that treatment with viable xenogeneic donor cells, CP, and mAbs against T and NK cells can induce a temporary peripheral mixed chimerism and donor-specific prolongation of xenogeneic skin graft survival. The destruction with CP of T and B cells that are xenoreactive and thus proliferating after antigen stimulation, followed by mechanism other than intrathymic clonal deletion, may be the mechanism of the hyporesponsiveness in the present system.

Drug-induced tolerance to allografts in mice. IV. Mechanisms and kinetics of cyclophosphamide-induced tolerance

Mechanisms and kinetics of tolerance in AKR mice induced using i.v. priming with viable C57BL/6 spleen cells and treatment with cyclophosphamide 2 days later were analyzed. In this tolerance induction system, some lymphocyte populations mediating delayed foot-pad reaction and cytotoxic activity were resistant to tolerance induction and remained in a sensitized state after cyclophosphamide treatment. These populations were considered to be qualitatively distinct from populations sensitive to cyclophosphamide, because delayed foot-pad reaction and cytotoxic lymphocyte activity were stronger in tolerant mice than in control mice in the early stages of tolerance induction, but were not augmented after immunization with C57BL/6 spleen cells, C57BL/6 skin grafts, or EL4 tumor grafts in the absence of suppressor T cells. One of the important differences in these two lymphocyte populations may be the capacity for clonal expansion.