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Biomedical subjects

R Fawwaz

Publications and source records attributed to R Fawwaz.

At least 19 recordsLinked to original sources
PubMed1990

Specific immunosuppression by local lymphoid irradiation using subcutaneous injection of palladium-109 labeled allogeneic lymphocytes.

We have previously shown that intravenously administered palladium-109 labeled lymphocytes (Pd-L) migrated specifically to peripheral lymphoid organs where they caused selective lymphoid irradiation resulting in significantly prolonged cardiac allograft survival. This study evaluates the biodistribution of subcutaneously injected allogeneic Pd-L and the capacity of such labeled cells carrying a large dose of irradiation at a local site to attract and subsequently delete alloreactive T lymphocytes. It was hypothesized that subcutaneously administered allogeneic lymphocytes labeled with a large dose of palladium-109 will attract and then kill by irradiation the host effector cells which might permit prolongation of donor-specific allograft via partial clonal deletion. The results showed that 80% (injected dose) of subcutaneously injected allogeneic Pd-L remained at the site of administration while 20% of injected dose/gram was localized in the ipsilateral popliteal lymph node. No significant radioactivity was found in the other lymphoid and nonlymphoid organs. Pd-L effectively deleted the donor-specific effector cells, as measured by specific unresponsiveness to donor lymphocytes in mixed lymphocyte reaction. Donor cardiac allograft survival, however, was not prolonged over that found in naive recipient controls, although it was significantly prolonged when compared to cardiac allograft survival in controls sensitized by identical injections of unmodified subcutaneous allogeneic lymphocytes (mean survival time +/- SD of 6.5 +/- 0.8 vs. 3.0 +/- 0.6 days). These results suggest that partial clonal deletion of specific alloreactive cells achieved by this approach alone is insufficient to induce unresponsiveness to allografts in vivo.

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PubMed1985

Selective lymphoid irradiation. VI. Effect of palladium-109-labeled lymphocytes on rat cardiac allograft survival.

We have previously shown that pretransplant treatment with palladium-109 hematoporphyrin (Pd-H) and two small doses of antilymphocyte globulin (ALG) leads to donor-specific permanent acceptance of cardiac allografts in weakly histoincompatible rat combinations and significant prolongation of hearts in the ACI-to-Lewis strains. Pd-H also concentrates in nonlymphoid organs to a significant degree that is undesirable, so we have examined, in the present study, the efficacy of Pd-109 attached to lymphocytes in producing selective lymphoid irradiation and compared it with the immunosuppressive effect of Pd-H. Adoptive transfer of syngeneic lymphocytes labeled with palladium-109 (Pd-L) led to significant concentration of radioactivity in the peripheral lymphoid organs relative to the bone marrow (BM), intestine, thymus, and endocrine organs. The concentration of radioactivity in the spleen relative to BM and intestinal mucosa was 23:1 and 58:1, respectively. The immunosuppressive efficacy of a suboptimal dose of 3 mCi (one-third of the dose used in our earlier reports with Pd-H) administered via Pd-L (6 X 10(9) cells) at 4 days combined with 5 mg ALG at 2 days and 1 day prior to transplantation was compared in its effect on cardiac allografts with a similar dose of Pd-H (3 mCi) combined with ALG. The mean survival time (MST) of 6.5 +/- 0.4 days in untreated recipients was moderately prolonged to 14.6 +/- 3.0 days by Pd-H and ALG, and was not significantly different from an MST of 14.1 +/- 0.3 days achieved with 2 doses of ALG alone. Pretransplant treatment of Lewis rats with Pd-L and ALG produced a significant prolongation of ACI heart allografts to 30.5 +/- 3.1 days (P less than 0.001). These results suggest that Pd-L is more effective in prolonging rat cardiac allografts than a similar dose of Pd-H, and thus it may be a new method of selective lymphoid irradiation prior to transplantation.

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PubMed1985

Selective lymphoid irradiation. V. Synergism with pretransplant thymectomy or thymic irradiation in cardiac transplantation in rats.

Selective lymphoid irradiation (SLI) using palladium-109-hematoporphyrin (Pd-H), given four days prior to transplantation, combined with two doses of antilymphocyte globulin (ALG) (10 mg, days -2 and -1), was evaluated as a method of induction of permanent heterotopic cardiac allograft survival in the highly histoincompatible rat strain combination of ACI (RT1(1))-to-Lewis (RT1a). Both Pd-H and ALG localize poorly in the thymus, so this study evaluated whether thymic irradiation (TI) or thymectomy (TX) of the adult recipient results in indefinite allograft survival. Immunosuppression with Pd-H or ALG alone gave a mean survival time (MST) of 6.7 +/- 0.6 days, but the combination of the two agents led to an MST of 17.6 +/- 3.4 days. When TI was combined with Pd-H and ALG, cardiac allograft survival was prolonged to 50.2 +/- 13.9 days, but TI alone showed an MST of 10.3 +/- 1.8 days. Permanent cardiac allograft survival (greater than 250 days) was achieved in all thymectomized recipients treated with the combination of Pd-H and a brief course of ALG. These animals also accepted second-set skin grafts and rejected third-party skin grafts following more than 150 days of ACI cardiac allograft survival. Thymic irradiation, although effective in acting synergistically with SLI and ALG, led to prolonged, but limited allograft survival, although thymectomy with SLI and ALG is synergistic in prolonging allograft survival permanently without chronic immunosuppression.

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PubMed1984

Selective lymphoid irradiation and cyclosporin A in rat heart allografts.

Short-term peritransplant treatment utilizing 2-dose ALG and 1-dose Palladium-109-hematoporphyrin (PD-H) for selective lymphoid irradiation (SLI) leads to donor-specific permanent acceptance of heart allografts in the Fisher to Lewis rat model. The same treatment significantly prolongs survival of hearts transplanted to strongly histoincompatable , presensitized, and xenogeneic recipients. The purpose of this study was to evaluate synergistic effects of short-term, low-dose cyclosporin treatment and SLI in an attempt to develop a nontoxic protocol utilizing peritransplant treatment for immune preconditioning with minimal subsequent immunosuppression. Single-agent treatment alone with cyclosporin, ALG, or Pd-H resulted in a maximal mean graft survival time (MST) of 33 days. Immunosuppression with 1-dose Pd-H, 2-dose ALG, and low-dose cyclosporin (5 mg/kg) for 14 days doubled the MST to 78 days. Use of therapeutic-dose cyclosporin (20 mg/kg), given for just 3 days, was also quite effective, MST of 57 days with SLI and 43 days with ALG, but toxic; 3 of 12 recipients died of infection with functioning grafts. These results demonstrate that the use of low-dose cyclosporin over a short interval, when combined with peritransplant SLI, is a highly effective and safe method for prolonging heart allograft survival.

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PubMed1983

Recirculation of indium-111-labeled lymphocytes in normal and allografted rats.

The kinetics of lymphocyte recirculation in normal and allografted rats with acute cardiac rejection was studied with indium-111 (In-111) labeled splenic lymphocytes in two groups of rats. Group 1 consisted of subgroups of normal Lewis rats infused with In-111 labeled unsensitized syngeneic cells (group 1a); ACI-sensitized syngeneic cells (group 1b); and ACI spleen cells (group 1c). Four rats from each subgroup were killed at 3, 6, 18, and 24 hr after cell infusion for blood, spleen, mesenteric lymph node (MLN), thymus, bone marrow (BM), liver, kidney, muscle, and heart scintillation counts. Group 2 consisted of Lewis recipients of ACI cardiac allografts infused with normal or with ACI-sensitized syngeneic splenic cells. Four rats from each subgroup were killed daily until rejection (day 7) for isotope counts of various organs. In ungrafted rats (group I), splenic accumulation of unsensitized syngeneic cells fell from 50% of the total injected dose/g tissue at 3 hr to 28% at 24 hr, whereas it rose from 12% at 3 hr to 39% at 24 hr in MLN. In contrast, the sensitized syngeneic and allogeneic cells homed preferentially to the spleen with insignificant accumulation in the MLN throughout the experiment. The BM and liver showed moderate accumulation while the thymus and nonlymphoid organs had low concentrations of labeled cells at all times. Splenic accumulation of unsensitized syngeneic cells in allografted rats (group II) showed a steep rise from day 1, reaching a peak at day 3, followed by a plateau--but sensitized cells demonstrated a peak on day 4 followed by a sharp decline until rejection. Accumulation of unsensitized cells in the MLN was significantly higher (P less than 0.001) than that of sensitized cells throughout the study. There was a significant fall (P less than 0.001) in radioactivity of BM, thymus, liver, and nonlymphoid organs from days 1-7, and the cardiac allograft demonstrated a reciprocal sharp rise in radioactivity. There was a significant early accumulation (P less than 0.001) of sensitized cells compared with unsensitized cells in the cardiac allograft on day 1. This study shows that In-111 labeled donor cells bearing surface antigen different from that of the recipient were sequestered from the circulating pool and immobilized in the spleen, but labeled donor cells with similar surface antigen to that of the recipient were recruited into the lymph node lymphocyte recirculating pool. It further demonstrates the difference in migration patterns of normal and sensitized syngeneic cells during acute allograft rejection.

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PubMed1981

Use of indium-111-labeled cells in measurement of cellular dynamics of experimental cardiac allograft rejection.

This study evaluates the kinetics and utility of infused indium-111-labeled cells in detecting rejection in ACI to Lewis rat heart allografts. Syngeneic leukocytes, lymph node lymphocytes, and platelets were isolated and labeled with indium-111 (111In) oxine, respectively, and were infused i.v. into Lewis rats carrying beating ACI or syngeneic hearts from post-transplant days 0 to 6. Recipients were imaged serially at 24 hr after infusion of labeled cells followed by excision of both native and transplanted hearts for direct isotope count. Labeled leukocytes accumulative progressively in the allograft with the scan becoming positive by post-transplant day 4. The ratio of allograft to native heart isotope counts rose from 1.25 on day 1 to 10.07 (P less than 0.0001) on day 7. The Lewis recipients infused with labeled lymphocytes showed a positive scan on days 6 and 7 whereas the allograft to native heart isotope count ratio rose from 0.97 on day 1 to 5.33 (P less than 0.001) on day 7. Recipients infused with 111In-labeled platelets showed a positive scan on days 5 to 7 and the allograft to native heart isotope count ratio rose sharply from 2.56 on day 4 to 16.98 (P less than 0.005) on day 7. Syngeneic heart grafts failed to demonstrate significant accumulation of any of the labeled cell population. These studies confirm the importance of nonlymphocytic cells in cellular rejection, evaluate the kinetics of graft invasion by the various cell types, and suggest that the techniques used afford a method for a safe and an early detection of allograft rejection.

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