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Biomedical subjects

C F Shield

Publications and source records attributed to C F Shield.

At least 37 records · Page 2Linked to original sources
PubMed1997

Isoform switching of type IV collagen is developmentally arrested in X-linked Alport syndrome leading to increased susceptibility of renal basement membranes to endoproteolysis.

Normal glomerular capillaries filter plasma through a basement membrane (GBM) rich in alpha3(IV), alpha4(IV), and alpha5(IV) chains of type IV collagen. We now show that these latter isoforms are absent biochemically from the glomeruli in patients with X-linked Alport syndrome (XAS). Their GBM instead retain a fetal distribution of alpha1(IV) and alpha2(IV) isoforms because they fail to developmentally switch their alpha-chain use. The anomalous persistence of these fetal isoforms of type IV collagen in the GBM in XAS also confers an unexpected increase in susceptibility to proteolytic attack by collagenases and cathepsins. The incorporation of cysteine-rich alpha3(IV), alpha4(IV), and alpha5(IV) chains into specialized basement membranes like the GBM may have normally evolved to protectively enhance their resistance to proteolytic degradation at the site of glomerular filtration. The relative absence of these potentially protective collagen IV isoforms in GBM from XAS may explain the progressive basement membrane splitting and increased damage as these kidneys deteriorate.

Basement Membrane↗
PubMed1997

Nonenzymatic glycation of type IV collagen and matrix metalloproteinase susceptibility.

The glomerular basement membrane (GBM) is damaged in diabetes through complex mechanisms that are not fully understood. Prominent among them is nonenzymatic protein glycation leading to the formation of so-called advanced glycation end products (AGEs). We examined the effects of in vitro glycation of intact collagen type IV in bovine lens capsule (LBM) and kidney glomerular (GBM) basement membranes on their susceptibility to matrix metalloproteinases, using stromelysin 1 (MMP-3) and gelatinase B (MMP-9). Sites of cleavage of unmodified LBM collagen were located in the triple helical region. In vitro glycation by glucose severely inhibited the release of soluble collagen cleavage peptides by MMP-3 and MMP-9. The distribution of AGEs within the three domains of collagen IV (7S, triple helical, and noncollagenous NC1) were compared for LBM glycation using AGE fluorescence, pentosidine quantitation, and immunoreactivity towards anti-AGE antibodies that recognize the AGE carboxymethyllysine (CML). Marked asymmetry was observed, with the flexible triple helical domain having the most pentosidine and fluorescent AGEs but the least CML. The in vivo relevance of these findings is supported by preliminary studies of AGE distribution in renal basement membrane (RBM) collagen IV domains from human kidneys of two insulin-dependent diabetics and one normal subject. Pentosidine and fluorescent AGE distributions of diabetic RBM were similar to LBM, but the CML AGE in diabetic kidney was less in the triple helical domain than in NC1. Our results support the hypothesis that nonenzymatic glycation of collagen IV contributes to the thickening of basement membranes, a hallmark of diabetic nephropathy.

Adult↗
PubMed1996

HLA-DR and DQ typing by polymerase chain reaction using sequence-specific primer mixes reduces the incidence of phenotypic homozygosity (blanks) over serology.

Because of the inherent difficulties in allele assignment with HLA-DR serological typing, in 1993 our organ procurement organization-based HLA laboratory replaced serology with the molecular method of polymerase chain reaction using sequence-specific primer mixes (PCR-SSP) to type for DR and DQ at a resolution level equivalent to that of serologically defined antigens. In this study, we compared the incidence of DR blanks, where allocative homozygosity occurred, and graft outcome during our serology epoch (1987-1993) with that of our molecular epoch (1993-1996). The incidence of DR blanks by PCR-SSP (17.0%; 138/1101) was significantly lower (P<0.005) than in the serology epoch (21.5%; 569/2647). Although DQ is not a component of the allocation algorithm, the incidence of blanks in the molecular era (21.9%; 196/895) was 46% lower (P<0.001) than in the serology epoch (40.8%; 931/2277). Graft survival in 163 cadaveric renal transplant recipients for whom molecular DR allocation occurred (patient and donor were molecularly typed) showed that PCR-SSP typing had no significant effect on 2.5-year graft survival for patients mismatched for 0 (97%), 1 (90%), or 2 (94%) HLA-DR antigens (P=0.4; log-rank). In conclusion, molecular typing lowered the rate of DR and DQ blanks, but molecular matching for HLA DR and DQ did not influence graft outcome at 2.5 years.

Blood Grouping and Crossmatching↗
PubMed1996

Improved graft survival in cadaveric renal retransplantation by flow crossmatching.

OBJECTIVE: To evaluate the role of flow cytometry cross-matching on graft survival in patients undergoing cadaveric renal retransplantation compared with our conventional antihuman globulin cytotoxic crossmatch. DESIGN: In 1990, 6 of 7 transplantation centers in 1 organ procurement organization service area began performing cadaveric renal retransplantation only if the flow T-cell IgG crossmatch was negative. During that period, 1 center continued to use only the antihuman globulin T-cell IgG crossmatch. Prior to 1990, all centers used only the antihuman globulin T-cell IgG crossmatch as their crossmatch selection criterion for retransplantation. Regraft survival was compared between those centers by crossmatch selection criteria. PATIENTS: Patient selection and immunosuppression decisions were made at the transplantation center. SETTING: All flow cytometry crossmatches for all 7 centers participating in the evaluation were performed at the Histocompatibility Laboratory of the Midwest Organ Bank Inc, Westwood, Kan. RESULTS: Graft survival is significantly better (P = .03 [logrank test]) in regrafts when the flow crossmatch is used to select patients for transplantation. CONCLUSION: Flow crossmatching improves graft survival in cadaveric renal retransplantation by identifying a subset of patients with donor-directed HLA class I antibodies that are not detectable by our conventional antihuman globulin crossmatch.

Cadaver↗
PubMed1996

A cost-effectiveness analysis of OKT3 induction therapy in cadaveric kidney transplantation.

We evaluated the cost-effectiveness of a standard immunosuppressive regimen versus an OKT3 induction regimen in cadaveric kidney transplant recipients. Cost estimates were based on results from a five-center randomized trial comparing the safety and efficacy of OKT3 induction with a conventional triple-drug regimen and financial data from the National Cooperative Transplantation Study, the Medicare Provider and Analysis Review database, and other sources. Patients received OKT3 (5 mg/day) by intravenous (IV) bolus injection for 10 to 14 consecutive days in conjunction with azathioprine, prednisone, and the delayed addition of cyclosporine (CsA) on day 11 (n = 105) or a conventional immunosuppressive regimen consisting of CsA, azathioprine, and prednisone (n = 102). The following measures were used to evaluate the two regimens: costs incurred between transplantation and graft failure; the effectiveness of the two regimens as defined by length of graft survival; and cost-effectiveness ratios through 5 years of observed follow-up and modeled through the expected duration of graft survival. Results showed that OKT3 induction uniformly adds $8,219 to the cost of the transplant hospitalization. However, most of this cost is offset by a reduction in the cost of treating rejection episodes in the OKT3 group (P = 0.002). A trend toward improved graft survival was detected in the OKT3 group (P = 0.158). Through 5 years of observed follow-up, costs per year of graft survival are $30,474 with OKT3 versus $32,687 with the conventional regimen. Modeled through the expected duration of graft survival, OKT3 induction costs $8,335 for each additional year of graft survival. Results are fairly insensitive to wide variations in baseline assumptions. We conclude that OKT3 induction improves the cost-effectiveness of kidney transplantation.

Anti-Infective Agents↗
PubMed1996

OKT3 prophylaxis in renal grafts with prolonged cold ischemia times: association with improvement in long-term survival.

The data on patients participating in two randomized, prospective studies with similar immunosuppressive regimens were updated and combined to evaluate the long-term effects of OKT3 according to cold ischemia time (< or = or > 24 hr). Among 159 patients in the OKT3 and 153 in the cyclosporine A (CsA) group, 8 and 12 deaths occurred, respectively (P = NS). In patients with cold ischemia > 24 hours, OKT3 prophylaxis resulted in a lower mean number of rejection episodes per patient than did CsA prophylaxis within one year (mean +/- SEM: 0.87 +/- 0.11 vs. 1.35 +/- 0.14, respectively; P = 0.008) and within five years (1.07 +/- 0.12 vs. 1.49 +/- 0.15, respectively; P = 0.032). In contrast, rejection incidences in patients with cold ischemia < or = 24 hours was not significantly different in the two groups. In all study patients, there was a trend towards higher graft survival rates in the OKT3 group versus the CsA group (at 5 years, 73% vs. 66%, respectively; P = 0.182). Among recipients of kidneys with cold ischemia times > 24 hours, OKT3 patients had significantly higher graft survival than CsA patients at two years (84% vs. 64%, respectively) and at five years (71% vs. 56%, respectively; P = 0.045). Significant differences were not observed in recipients of kidneys with cold ischemia times < or = 24 hours. In conclusion, patients receiving renal grafts with long cold ischemia times strongly benefit from OKT3 prophylaxis.

Adult↗
PubMed1995

Detection of HLA IgG antibodies by two enzyme-linked immunoassays, solubilized HLA class I and PRA-STAT. Comparison with the AHG PRA.

HLA class I-directed IgG antibodies have traditionally been detected with a complement-dependent lymphocytotoxicity (CDL) technique. We have evaluated two solid-phase enzyme-linked immunoassays (EIA) and compared them with the CDL antihuman globulin (AHG) dithiothreitol-treated (DTT) PRA in their ability to discriminate between the presence or absence of HLA class I-directed IgG antibodies in serum from patients awaiting transplantation. The EIA were: (1) an EIA that uses solubilized HLA class I antigens (sHLA-I) isolated from a 240-member platelet donor pool, and (2) the PRA-STAT ELISA kit. For the first comparison, we used 691 serum samples from 272 patients taken before they had been transplanted. The data show a significant (P < 0.0001) linear correlation (r = 0.77 between the AHG DTT PRA and the sHLA EIA. They also demonstrate that the mean sHLA-I EIA ratio significantly increases (P < 0.01) above background levels with each stepwise increase in AHG DTT PRA level. Discordant results were 1.0% (7/691) for sHLA-I EIA+ PRA- and 6.3% (44/691) for PRA+ sHLA-I EIA-. However, a lower correlation was noted between the AHG DTT PRA and the PRA-STAT (Nextran) PRA results (n = 230; r = 0.42). The sHLA-I EIA is able to determine whether or not HLA Class I IgG antibodies are present in serum from transplant candidates and is an appropriate adjunct to the traditional CDL PRA assay, whereas the PRA-STAT is not.

Enzyme-Linked Immunosorbent Assay↗
PubMed1995

The OKT3 Antibody Response Study: a multicentre study of human anti-mouse antibody (HAMA) production following OKT3 use in solid organ transplantation.

Human anti-murine antibody titres following patient exposure to the monoclonal antibody Orthoclone OKT3 (muromonab-CD3) are determined by laboratories using diverse analytical methods which are not standardized and whose concordance is not established. A multicentre study group therefore compared testing for IgG anti-OKT3 antibody among seven laboratories. A set of 270 sera was obtained from 30 heart, 30 kidney and 30 liver transplant recipients with no previous exposure to OKT3 who were receiving OKT3 for induction immunosuppression. Sera were collected from each patient prior to and at 24 +/- 2 days and 31 +/- 2 days following initial OKT3 exposure. Identical aliquots of all 270 sera were tested for IgG anti-OKT3 antibody by each laboratory. In addition, the limit of detection of each laboratory's method was estimated by titration of an affinity-purified IgG anti-OKT3 reference material of known concentration. Anti-OKT3 antibody formation differed greatly among the three organ groups. Cardiac patients demonstrated the least sensitization and almost exclusively lower titres, while kidney recipients had more frequent and higher titre antibody formation. Liver recipients yielded the highest sensitization rate and the most frequent high titre sera. Importantly, the seven laboratories differed widely in the number of pretreatment sera reported as positive (ranging from 0% to 41% among laboratories), the number of post-OKT3 sera reported as positive (17-63%), the number of post-OKT3 samples with titre > or = 1000 (2-31%), and the number of patients sensitized 19-69%). Concordance among laboratories was highly variable, with interlaboratory agreement ranging from 38% to 83% on the sample titres assigned to 180 post-OKT3 sera. Many of the discordant results were consistent with differences in the limit of detection of the analytical methods, which ranged from 0.19 microgram/ml to > or = 15 micrograms/ml, a nearly 100-fold difference among laboratories. This study demonstrated the presence of both good concordance and significant discordance among laboratories in determining human anti-mouse antibody titres, and demonstrated that common titre categories (100, 1000, 10,000) were not equivalent among laboratories. The level of concordance among methods should be considered when comparing anti-OKT3 antibody results from different centres and their correlation with clinical events. Universal comparative testing, patterned after proficiency testing programmes, is needed to assess differences among laboratories and to bring uniformity and a sound interpretative basis to this field of testing.

Adult↗
PubMed1993

A randomized clinical trial of induction therapy with OKT3 in kidney transplantation.

A randomized, prospective multicenter trial was conducted to compare the safety and efficacy of OKT3 as an induction therapy with that of conventional immunosuppressive therapy administered to cadaveric renal allograft recipients. Two hundred fifteen patients were treated either with OKT3 plus azathioprine and steroids for 14 days with the delayed addition of cyclosporine on day 11, or with conventional immunosuppression (steroids, azathioprine, and cyclosporine). OKT3 patients had significantly fewer rejection episodes (51% vs. 66%, P = 0.032), a longer time to initial rejection (46 days vs. 8 days, P = 0.001), and fewer rejection episodes per patient (0.82 vs. 1.14, P = 0.014) than conventionally treated patients. Kaplan-Meier estimates of two-year graft and patient survival rates were 84% and 95%, respectively, for the OKT3-treated group, and 75% and 94%, respectively, for the conventionally treated group. Following a subsequent first rejection episode, OKT3 reversed 93% of the rejections in patients receiving OKT3 induction therapy and 94% in patients receiving conventional therapy. Adverse experiences reported during OKT3 induction therapy were similar to those seen when the drug was used for rejection. Following initial exposure, 40.3% of the patients tested were positive for anti-OKT3 antibody, only 6.7% of which were of high titer (1:1000). In the presence of low titer (1:100 or less) antibody, OKT3 was successful in reversing rejection in five of six retreated patients tested. In conclusion, treatment with OKT3 (in combination with azathioprine, steroids, and the delayed addition of cyclosporine) is an effective approach for renal allograft maintenance.

Adolescent↗
PubMed1993

The effects of intraoperative administration of OKT3 during renal transplantation.

The use of the monoclonal antibody OKT3 for induction immunosuppression in renal transplantation is increasing--however, the safety of intraoperative administration continues to be questioned because of first-dose effects. The current study was designed to examine the effects of intraoperative administration of OKT3 on the cardiovascular and pulmonary systems in 161 consecutive renal transplant recipients. Patients receiving OKT3 intraoperatively during renal transplant (99 cadaver recipients) were compared with 62 patients not administered the drug (31 cadaver, 25 living-related-donor, 6 living-nonrelated donor). Intraoperative airway pressure (highest, average), O2 saturation (SaO2), temperature, blood pressure changes, cardiac rhythm, and bronchospasm were compared in these two groups. Significant physiologic changes noted in the group receiving OKT3 included increased temperature (both intraoperative and postoperative), decreased SaO2 (postoperative), and increased FiO2 (postoperative). Despite these differences, no clinically significant changes were noted in the group receiving OKT3. OKT3 induction given at the time of surgery was associated with a significantly increased one- and three-year graft function. This study demonstrates that first-dose administration of OKT3 intraoperatively during renal transplantation is safe and effective.

Adult↗