Complement activation by whole endotoxin is blocked by a monoclonal antibody to factor B.

Sepsis is both a common and, despite present-day therapy, a serious disease. The pathophysiology of the septic response is a complex, multifactorial phenomenon which in part involves the activation of complement by bacterial endotoxin. A monoclonal antibody to human complement factor B, code-named 1H5, which was capable of specifically inhibiting the alternative pathway of complement activation at concentrations as low as 1 microgram/ml, is described. This agent had no effect on the classical pathway of complement activation. It was capable of preventing the activation of complement by even high concentrations (0.1 mg/ml) of whole endotoxin; however, it was ineffective in preventing activation of complement by endotoxin derived from a rough mutant. This agent could potentially be used in the treatment of sepsis.

Urine-to-blood carbon dioxide tension gradient and maximal depression of urinary pH to distinguish rate-dependent from classic distal renal tubular acidosis in children.

We determined the prevalence and clinical features of rate-dependent distal renal tubular acidosis (dRTA) in 31 children examined for possible renal tubular acidosis by measuring the urinary-minus-blood partial pressure of carbon dioxide (U-B PCO2) gradient, minimal urinary pH, and fractional excretion of bicarbonate. Of 20 patients with low U-B PCO2 gradients, nine could not lower urinary pH < or = 5.5, indicating classic dRTA, whereas 11 could lower urinary pH < or = 5.5, as described in rate-dependent dRTA. When patients with rate-dependent dRTA and classic (type I) dRTA were compared, there was no difference in the mean U-B PCO2 gradient or in clinical findings, including age, reason for referral, presence of nephrocalcinosis, or depression of linear growth. We conclude that children with rate-dependent dRTA are susceptible to at least some of the same sequelae as children with classic dRTA. Measurement of minimal urinary pH will not detect this subtle form of dRTA. Determination of the U-B PCO2 gradient should be considered a routine part of evaluation for suspected renal tubular acidosis in a child.

Complement activation and lung permeability during cardiopulmonary bypass.

Pulmonary dysfunction after cardiopulmonary bypass has been attributed to the damaging effects of complement activation on the lung. To further explore this phenomenon, we measured plasma levels of activated complement components (radioimmunoassay), assessed neutrophil n-formyl-methionyl-leucyl-phenylalanine (FMLP) receptor status (radioligand saturation binding assay), and quantified pulmonary epithelial permeability as radioaerosol lung clearance of technetium 99m-labeled diethylenetriamine pentaacetic acid in a series of 8 patients undergoing cardiopulmonary bypass. Significant elevations of plasma C3adesArg, C4adesArg, and C5adesArg levels were seen just after CPB, indicating activation of both the classic and alternate complement pathways. Neutrophil activation was evident as increased expression of neutrophil FMLP surface receptors after bypass. Despite the presence of complement and neutrophil activation, increased pulmonary epithelial permeability was not seen. These data support the hypothesis that complement and neutrophil activation during cardiopulmonary bypass is not associated with acute lung injury, at least not pulmonary epithelial injury. One can therefore infer that increased pulmonary epithelial permeability in patients at high risk for and experiencing sepsis-induced and trauma-induced adult respiratory distress syndrome may be due to factors other than complement and neutrophil activation.

Autoantibody to complement neoantigens in membranoproliferative glomerulonephritis.

With the exception of C3 nephritic factor, autoantibody formation has not been commonly associated with membranoproliferative nephritis (MPGN). We measured autoantibodies (nephritic factors) to the C3 convertases C3bBb (NFa) and C3bBbP (NFt), which result in fast and slow C3 activation, respectively, and to a neoantigen on C1q fixed to a solid phase (spC1q) in sera from 29 patients with MPGN type I, 26 with type II, and 28 with type III. Autoantibody formation was common in all MPGN types. An autoantibody to a C3 convertase neoantigen was identified in more than 75% of the hypocomplementemic MPGN sera tested. Anti-C3bBb (NFa) was present in 81% of patients with MPGN type II but was rarely found in either type I or type III. Anti-C3bBbP (NFt) was common in both MPGN I and III. Anti-spC1q was present in 74% of patients with type I and in 38% and 48% of types II and III MPGN, respectively. Patients with MPGN types I, II, and III had one and two serum autoantibodies detected significantly more frequently than did a group of healthy subjects. The presence of any one autoantibody was not specifically associated with the presence of any other autoantibody. The results indicate that multiple autoantibody formation is common in all MPGN types. MPGN II, and possibly MPGN I, tend to form more specific autoantibodies.

Serum terminal complement component levels in hypocomplementemic glomerulonephritides.

Measurements of serum C3 through C9 are reported for patients with acute poststreptococcal glomerulonephritis (AGN), membranoproliferative glomerulonephritis type I (MPGN I), MPGN II, and MPGN III. Except in MPGN II, depressed C5 levels correlated with depressed C3 levels. In MPGN II, levels of C5 and of other terminal components were normal. In MPGN III, markedly depressed levels of C7 through C9 correlated strongly with depressed levels of C3 and C5. C6 was less severely depressed. In MPGN I, terminal component levels were less often depressed than in MPGN III and in AGN, depression of terminal components was seen only when levels of C3 and C5 were extremely low. The data indicate that late terminal components are activated in MPGN III to a greater extent than in the other nephritides despite C5 activation approximately equal in extent to that in AGN and MPGN I.

A properdin dependent nephritic factor slowly activating C3, C5, and C9 in membranoproliferative glomerulonephritis, types I and III.

The IgG fraction of serum from patients with membranoproliferative glomerulonephritis (MPGN) types I and III was found to contain a nephritic factor (NFI/III) which differed from that usually present in MPGN type II and partial lipodystrophy (NFII) in that it converts C5 and C9 as well as C3, is dependent on properdin for its activity, and requires an incubation period of several hours rather than 30 min for its demonstration. C3 conversion occurred in the absence of an intact classical pathway. This nephritic factor was found in patients with reduced serum levels of terminal components and its activity, like that of the nephritic factor in MPGN type II, correlated with the serum C3 level indicating that these nephritic factors play a large role in producing hypocomplementemia. Although potentially nephritogenic because of its ability to activate the terminal pathway, the presence of this nephritic factor did not clearly correlate with clinical course.

Clinical variability of cyclosporine pharmacokinetics in adult and pediatric patients after renal, cardiac, hepatic, and bone-marrow transplants.

The most important limitation associated with the clinical use of cyclosporine is the narrow therapeutic range between its efficacy and toxicity. Effective treatment is further complicated by significant variation in intrapatient and interpatient pharmacokinetics of the drug. We describe a practical approach to pharmacokinetic analysis that does not interfere with the cyclosporine dosage regimen or with clinical management of the patient. To optimize therapy, we individualized patient management by using noncompartmental pharmacokinetic analysis. Mean residence time (MRT) and volume of distribution at steady-state were calculated from data on concentration vs time after dose. We applied this approach to 24 kidney, 12 heart, 8 bone-marrow, 7 liver, and 5 pancreas transplants. Individualized requirements for cyclosporine dose and dosage interval can be predicted from these parameters. MRT is the most useful pharmacokinetic parameter, because it allows prediction of the optimal dosage interval.

Cyclosporine pharmacokinetics in pancreas transplant recipients.

Ten CsA pharmacokinetic studies were performed on five pancreas transplant recipients to determine proper doses and dosing intervals. These cadaver pancreas transplants were performed with exocrine ductal drainage into the urinary tract through a bladder anastomosis in four cases and into the bowel in one case. Four CsA pharmacokinetic studies were performed on diabetic renal transplant recipients and an additional six studies were performed while with pancreas transplant patients taking metoclopramide in an effort to enhance absorption of CsA. Mean CsA dose was 3.7 mg/kg/dose (range 2.1 to 7.5 mg/kg/dose). All patients but one were on twice daily dosing intervals yielding an average daily dose of 7.4 mg/kg/d. Noncompartmental pharmacokinetic analyses were used. The adequacy of a 1-, 2-, or 3-exponential model was determined by breakpoint analysis of the log concentration v time curve using the F statistic. The terminal rate constant was calculated by nonlinear regression analysis. The AUC and AUMC were calculated by the trapezoidal method with exponential extrapolation and these were used to calculate the MRT and Vdss. The unknown fractional absorption, F, was used to correct the oral data. The average CsA concentration maximum (Cmax) was 528 ng/mL with an average time to maximum concentration (Tmax) of 4.7 hours, a mean residence time of 7.75 hours, with a Vdss/%F of 9.61 L/kg in the pancreas transplant recipients. Additional studies of six patients receiving metoclopramide with CsA revealed an average Cmax of 723 ng/mL, an average Tmax of 2.3 hours, an average MRT of 6.08 hours, and an average Vdss/%F of 5.7% L/kg. These results indicate that coexistent gastroparesis in diabetic recipients of either pancreatic or renal transplants may result in reduced bioavailability of CsA.

Use of cyclosporine and ketoconazole without nephrotoxicity in two heart transplant recipients.

A cyclosporine-ketoconazole drug interaction was first described in 1981. It has been suggested that the two drugs should not be used concomitantly because of the danger of severe nephrotoxicity. Two reported cases indicate that cyclosporine and ketoconazole can be safely coadministered, provided that the dosage of cyclosporine is reduced appropriately. Two patients were initially given 8 mg/kg/day of cyclosporine at the time of heart transplantation, and the dosage was tapered to meet appropriate blood levels (250 to 350 ng/ml by whole blood high-performance liquid chromatography). During ketoconazole therapy (400 mg daily for 4 weeks), patient 1 received 80 to 100 mg/day of cyclosporine, which is equal to approximately 1 mg/kg/day, and patient 2 received between 40 and 80 mg/day of cyclosporine, which is equivalent to 0.4 to 0.8 mg/kg/day. Neither patient exhibited a creatinine value above 1.4 mg/dl while on combined therapy, and there were no problems with allograft rejection. Both patients had inappropriately high cyclosporine blood levels even with this marked reduction in dosage (patient 1, 520 to 1310 ng/ml and patient 2, 320 to 600 ng/ml). Thus it appears that cyclosporine and ketoconazole can be administered together safely, provided that there is an appropriate reduction in the dosage of cyclosporine; this results in the maintenance of adequate immunosuppression without development of nephrotoxicity.

Increased susceptibility to infection in hypothermic children: possible role of acquired neutrophil dysfunction.

The addition of hypothermia to regimens to control cerebral edema in children at our institution has been associated with a substantial incidence of infectious complications. Of the 13 children maintained at 30 degrees C to prevent cerebral edema, 3 developed Haemophilus influenzae pneumonia and 2 developed Streptococcus pneumoniae sepsis (one with pneumonia). The importance of neutrophil (PMN) function for elimination of bacterial pathogens prompted in vitro studies of PMN function at clinically attainable hypothermic temperatures. Neutrophils at 30 degrees C had significantly less ability to migrate towards a chemotactic stimulus (45 +/- 10% inhibition; P less than 0.02), to ingest staphylococci (22 +/- 5% inhibition; P less than 0.01) and to be metabolically activated as measured by superoxide production (35 +/- 10% inhibition; P less than 0.01) or by chemiluminescence (18 +/- 8% inhibition; P less than 0.05). These in vitro findings support the clinical observation that persons with decreased body temperature may be at an increased risk for bacterial infections secondary to PMN dysfunction.