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Biomedical subjects

F P Stuart

Publications and source records attributed to F P Stuart.

At least 37 records · Page 2Linked to original sources
PubMed1991

OKT3 therapy for hepatic allograft rejection. Differential response in adults and children.

The clinical courses following OKT3 therapy for hepatic allograft rejection (HAR) in adults and children have not been individually defined. We have reviewed our experience with OKT3 therapy for HAR in adults and children to compare: (1) the initial response to OKT3 therapy, (2) the clinical course following OKT3 therapy, and (3) the antimurine antibody response and immunologic monitoring results. Children required OKT3 therapy more frequently than adults: fourteen courses of OKT3 therapy were required in 130 orthotopic liver transplants (OLT) in 108 adult patients, whereas nineteen courses of OKT3 therapy were required in 94 OLT in 78 children (P less than 0.02). Repeat OKT3 therapy was not required in adults--however, four of nineteen courses of OKT3 therapy in children were repeat OKT3 therapy for rejection. No differences existed between adult and pediatric treatment groups with respect to number of prior OLT procedures, previous graft loss to rejection, percentage of ABO-incompatible grafts, frequency of positive donor-recipient lymphocyte crossmatches, or time to first rejection. The initial response to OKT3 therapy (rapid reversal, delayed reversal, and failure) was remarkably similar in adults and children. However, nine of 13 (70%) children with clear evidence of response to OKT3 treatment experienced breakthrough rejection or early recurrent rejection, whereas none of 12 adults suffered breakthrough rejection or early recurrent rejection (P less than 0.01). Early recurrent rejection did not correlate with delayed reversal of rejection, early return of CD3+ cells by peripheral blood monitoring, or development of anti-OKT3 antibodies. All 4 courses of OKT3 retreatment in children were successful in reversing rejection, and breakthrough rejection and early recurrent rejection did not occur. Overall graft and patient survival in pediatric patients requiring OKT3 therapy (67% and 73%) was not different from that in adults (71% and 79%). Results obtained in one patient provide the first evidence that successful OKT3 retreatment of HAR can be achieved in the presence of preexisting idiotypic anti-OKT3 antibody. In conclusion, OKT3 therapy for HAR was required more frequently in children than in adults. The clinical outcome following OKT3 therapy for HAR also differs markedly, with early recurrent rejection and breakthrough rejection occurring more frequently in children.

Adult↗
PubMed1991

OKT3 F(ab')2 fragments--retention of the immunosuppressive properties of whole antibody with marked reduction in T cell activation and lymphokine release.

Recent studies in mouse and man indicate that the first dose response to anti-CD3 mAbs likely results from in vivo T cell activation and concomitant lymphokine release. One approach toward amelioration of these effects involves the use of nonactivating digest fragment preparations of anti-CD3 mAbs. In the present study whole and F(ab')2 fragments of OKT3 were prepared and assayed for their immune-activating and -suppressing effects on human peripheral blood mononuclear cells. Immunosuppressive effects were evaluated by quantitation of TCR modulation and coating, and by inhibition of CTL activity. Whole mAb and F(ab')2 fragments both effectively coated the TCR complex. However, whole mAb was more efficient at modulating the TCR complex, suggesting that modulation is enhanced by FcR interactions. Whole and F(ab')2 fragments of OKT3 were equally efficacious in suppressing CTL activity. Immune activation was evaluated by quantitation of proliferation, activation marker expression (IL-2R and Leu-23), and lymphokine release (TNF-alpha, gamma-IFN, and GM-CSF). Rigorously purified F(ab')2 preparations demonstrated minimal T cell activation, suggesting TCR and macrophage FcR crosslinking as necessary. Whole OKT3 mAb induced expression of IL-2R and Leu-23 activation markers on the majority of CD4+ and CD8+ cells at mAb concentrations as low as 1 ng/ml, whereas F(ab')2 fragments induced detectable, but markedly reduced expression of these markers only at mAb concentrations greater than or equal to 100 ng/ml. Similarly, whole mAb induced release of TNF-alpha, gamma-IFN, and GM-CSF at low mAb concentrations, whereas F(ab')2 fragments induced detectable (though markedly reduced) levels of TNF-alpha only. However, increasing degrees of contamination with whole antibody resulted in increasing mitogenic potency of the F(ab')2 preparation, which in some cases, was actually enhanced compared with that observed with whole mAb alone. In conclusion, these studies indicate that OKT3 F(ab')2 digest fragments are markedly less potent than whole mAb in inducing T cell activation, yet they retain significant immunosuppressive effects. However, meticulous purification of F(ab')2 digest fragment preparations will likely be required to avoid T cell and macrophage activation following in vivo administration.

Antibodies, Monoclonal↗
PubMed1991

Elevated lipoprotein(a) levels in renal transplantation and hemodialysis patients.

Hyperlipidemia poses a risk for cardiovascular disease in both hemodialysis and renal transplantation patients. Although lipid profiles differ between the 2 populations, we evaluated the possibility that both groups have similar abnormalities of lipoprotein(a) [Lp(a)]. Mean serum Lp(a) and standard error of the mean (SEM) in hemodialysis and transplant recipients was 16.6 +/- 4.7 and 18.3 +/- 3.6 mg/dl, respectively, compared with 10.7 +/- 4.1 mg/dl in healthy controls, p less than 0.05. That serum Lp(a) levels are significantly elevated in dialysis and renal transplantation patients suggests at least 1 common pathogenic mechanism for the high incidence of atherosclerosis in both groups.

Adult↗
PubMed1991

Anti-CD3 monoclonal antibody therapy. An approach toward optimization by in vitro analysis of new anti-CD3 antibodies.

Several problems remain associated with anti-CD3 monoclonal antibody therapy, including first-dose reactions, recurrent rejection, and the host humoral response to the xenogeneic mAb. One approach toward optimization of anti-CD3 mAb therapy involves the use of anti-CD3 mAbs of defined idiotype, isotype, and epitope specificity, so that the desired T cell activation and suppression properties are obtained and neutralization by antiidiotypic antibody is avoided. The purpose of the present study was to define the contribution of mAb isotype and epitope specificity in determining T cell activation and suppression potencies and to evaluate the idiotypic relationships among ten anti-CD3 mAbs and one anti-TCR alpha beta mAb selected for this study. Epitope mapping by flow cytofluorometry indicated that one mAb, OKT3D, possesses an epitope specificity distinct from that of other anti-CD3 mAbs. Analysis of early T cell activation, proliferation, and lymphokine production (TNF-alpha, gamma-IFN, and GM-CSF) indicated that mAb isotype exerted a profound effect on activation potency (IgG2a much greater than IgG1 greater than IgG2b), whereas epitope specificity exerted a minor effect. CTL inhibition studies demonstrated an epitope effect with highest inhibition potencies observed with OKT3D IgG1 and OKT3D IgG2b mAbs. Idiotypic analysis of nine mAbs indicated that all anti-CD3 mAbs except OKT3E possess idiotypes distinct from that of OKT3. Thus, two anti-CD3 mAbs, OKT3D IgG1 and OKT3D IgG2b, possess high immune suppression potency, low activation potency, and idiotypes distinct from OKT3. In conclusion, selection of anti-CD3 mAbs of defined idiotype and appropriate T cell activation and suppression properties may provide a means for mitigating problems associated with OKT3 therapy.

Antibodies, Anti-Idiotypic↗
PubMed1989

Pancreas-graft immunogenicity and pretreatment with anti-class II monoclonal antibodies.

Pretreatment of organ allografts to reduce graft immunogenicity is an attractive and potentially clinically applicable concept. We have studied the effect of perfusing rat pancreases with anti-class II monoclonal antibody (MoAb), to remove class II- positive accessory cells from the intact organ, on prolongation of allograft survival after transplantation. The capacity of pancreatic islets obtained from these perfused organs to stimulate proliferation of allogeneic T-lymphocytes was studied in a mixed islet-lymphocyte culture (MILC). There was a significant prolongation in pancreas-allograft survival when intact pancreases were transplanted after a 3-h normothermic perfusion with MoAb reactive with class II antigens (16.2 +/- 3.6 days, n = 19) compared with control animals (11.0 +/- 1.4 days, n = 24). In vitro treatment of islets with MoAb and complement (CI) inhibited their stimulatory capacity in the MILC, as measured by [3H]thymidine uptake. Similarly, the stimulatory capacity of islets removed from perfused pancreases was also abrogated when MoAb was included in the perfusate. Although reduction in graft immunogenicity, by increasing allograft survival, was achieved by a 3-h pretreatment regimen, it was not sufficient to inhibit rejection altogether in our transplant model.

Animals↗
PubMed1989

Selective OKT3 induction therapy in adult cadaveric-donor renal transplant recipients.

Decreasing Medicare reimbursement for renal transplantation has placed a premium on early hospital discharge. On average, the diagnosis-related group reimbursement for renal transplantation is exhausted by the ninth hospital day at the authors' institution. Previously, the median length of hospital stay was 14 days for patients with initial graft dysfunction and 8 days for those with immediate function. In the present protocol, all patients received a single 10-mg dose of OKT3 during the transplant procedure. Those with good initial function received no further OKT3 and began receiving cyclosporine, 10 mg/kg/d, on the second posttransplant day. High-dose cyclosporine was avoided in those with poor initial function, whether they required dialysis or not. Instead, they received cyclosporine, 6 mg/kg/d and resumed OKT3, 5 mg/d, on the second day for up to a 14-day course to prevent rejection during recovery of renal function and permit early discharge. All patients received maintenance immunosuppression including cyclosporine, azathioprine, and prednisone. Of 39 adult cadaveric-donor renal transplant recipients entered in the protocol with 2 to 8 months follow-up, 13 (33%) had good graft function and received only the intraoperative dose of OKT3, 9 (23%) had poor initial function but did not require dialysis, and 17 (44%) had poor function receiving dialysis for a median duration of 15 days (range, 2-46 days). Side effects of OKT3 were well tolerated, and median hospital stays were 7 days (range, 6-11), 7 days (range, 5-14), and 9 days (range, 5-15), respectively, for the three groups. Overall patient survival was 100% and graft survival was 97% for the short follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Radioimmunoscintigraphy and radioimmunotherapy in nude mouse models. Studies with site-specifically modified monoclonal antibodies.

Site-specific covalent modification of monoclonal antibodies at the oligosaccharide offers advantages over more conventional modification processes that involve direct attachment at tyrosine, lysine or glutamic/aspartic acid side chains. Using the site-specific modification process, attachment sites on the antibody are distal to the antigen-binding region. Thus, homogeneity of antigen-binding properties and affinity for the unmodified protein are preserved. Furthermore, higher derivatization ratios with no resultant loss of immunoreactivity can be achieved for monoclonal antibodies modified at the oligosaccharide. In vivo biodistribution and tumor localization studies in nude mouse models suggest that antibodies radiolabeled at their oligosaccharide might represent improved immunoscintigraphic reagents. In a variety of tumor xenograft models, site-specific modified 111In-labeled antibody conjugates localized to the tumor site with little non-specific localization in other tissues or organs. The degree of localization at the target site was substantially greater than that of 111In-labeled antibodies directly modified at the tyrosine side chain. Preliminary studies with 212Bi- and 90Y-labeled antibodies modified at the oligosaccharide indicate that both of these radioisotopes have immunotherapeutic potential. Because of its preferential uptake by the kidney, the use of 212Bi may be best suited for tumors localized within the peritoneal cavity, such as ovarian and colorectal carcinomas. The toxicity of 90Y at high specific activities suggests that a regimen of repeated smaller doses of this radioisotope is best suited for therapeutic use. Studies in tumor-bearing mouse models are currently underway to better define the optimal dosage and administration regimens for both of these radioisotopes when attached to site-specific modified antibodies.

Animals↗
PubMed1988

Use of a brief steroid trial before initiating OKT3 therapy for renal allograft rejection.

OKT3 (Ortho Pharmaceutical, Raritan, NJ) has been employed in a protocol where all patients received cyclosporine as part of their baseline immunosuppressive regimen and, after the diagnosis of rejection was established, were treated with up to three pulses of methylprednisolone before monoclonal antibody therapy was initiated. Use of this protocol has allowed 46% of rejection episodes encountered to be treated on an outpatient basis without resorting to inpatient use of OKT3, but has avoided delaying OKT3 therapy until after all other methods of rejection treatment were found to be ineffective. Of 83 rejection episodes treated with OKT3 between March 1985 and May 1987, 78 (94%) were reversed. Overall graft survival is 84% and patient survival is 96% in OKT3-treated patients. Of the 17 rejection episodes where OKT3 treatment was a second or third exposure to the drug, rejection was successfully reversed in 15 (88%). In cadaver donor allograft recipients transplanted between March 1985 and May 1986, actual 1-year graft survival is 80% for 30 patients requiring no rejection therapy, 80% for 20 patients with rejection episodes responding quickly to steroids, and 82% for 28 patients with OKT3-treated, steroid-insensitive rejections. Mean serum creatinine at 1 year posttransplant is 1.5 +/- 0.5; 1.9 +/- 0.7; and 2.1 +/- 0.8, respectively, for these groups of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1988

Complications and monitoring of OKT3 therapy.

Complications of OKT3 therapy were studied in 122 treatment episodes in renal allograft recipients (83 for rejection treatment, 39 for immunosuppression induction). A febrile first-dose reaction to OKT3 was common; no severe pulmonary complications were encountered. Other toxicities of OKT3 therapy were observed later in the treatment course. Most severe were the occurrence of aseptic meningitis in four patients (3%), and seizures in eight (6%). Seizures occurred only when OKT3 was given to patients with nonfunctioning grafts due to acute tubular necrosis. Infections were the only significant late adverse sequelae of OKT3 therapy and occurred more frequently after multiple exposures to the drug (53%) than after a single exposure (22%). IgG antibodies to OKT3 developed after 45% of exposures to the drug in the 74 patients in whom appearance of anti-OKT3 antibodies was monitored. In two patients (3%), anti-OKT3 antibodies were detected before the end of the OKT3 treatment course, neutralizing the immunosuppressive property of the drug. In five patients (7%), strong anti-OKT3 antibody responses were present at the time of subsequent rejection, which precluded reuse of the drug. In 17 other cases, no or only a weak anti-OKT3 response was detectable at the time of rejection following initial OKT3 exposure. Retreatment with OKT3 was successful in reversing rejection in 15 cases (88%). No untoward sequelae were noted after reexposure to OKT3, except the high incidence of subsequent infections.

Adult↗
PubMed1988

Cellular pathways for rejection of class-I-MHC--disparate skin and tumor allografts.

We have investigated the relative roles of the Lyt-2+ and L3T4+ T lymphocyte subsets in rejection of class-I-MHC-antigen-disparate skin and tumor allografts. To deplete T cells in vivo, rat anti-Lyt-2 or anti-L3T4 monoclonal antibodies (mAb) were administered to adult-thymectomized (ATX) recipient mice prior to transplantation. BALB/c (H-2d) recipient mice rejected the Ia- Sarcoma I (Sa1) (H-2a) tissue culture-derived tumor after depletion of the L3T4+ T cell subset in vivo. In contrast, depletion of the Lyt-2+ T cell subset permitted lethal tumor growth in all recipient mice. To determine the role of particular T cell subsets in rejection of Ld class-I-MHC-antigen-disparate allografts, BALB/c skin was transplanted to BALB/c-H-2dm2 recipient mice. Skin grafts were rejected by control mice with a mean survival time (MST) of 14.5 days. The MST of skin grafts for mice treated with anti-L3T4 mAb was 16.6 days. In contrast, administration of anti-Lyt-2 mAb alone (MST = greater than 47 days) or together with anti-L3T4 mAb (MST = greater than 50 days) caused prolonged or indefinite graft survival in all recipient mice. Depletion of specific T cell subsets was confirmed by flow cytometric analysis and by analysis of T cell function in vitro. These results suggest that Lyt-2+ T lymphocytes are essential for rejection of class-I-MHC-disparate allografts; indirect presentation of alloantigen to L3T4+ T cells may not be necessary for rejection.

Animals↗