Roger E Spitzer

Activity of the alternative pathway of complementin the newborn infant

Levels of C3, properdin, factor B, and C3 to C9 activity were markedly reduced in cord sera taken from 94 normal newborn infants. Nevertheless, cord serum supported complete activation of its own alternative pathway by zymosan or CoF. Lysis of a target cell, however, was defective; nearly 75% of cord sera had reduced rabbit erythrocyte CH50 titers. These were partially increased by the addition of factor B and properdin, and totally restored by adding factor B, properdin, and C3 to C9. Therefore, although the alternative pathway of the neonate is intact, it appears to be limited in its ability to generate an adequate number of stable and active enzymatic sites on a target cell membrane.

Evidence that production of autoantibody to the alternative pathway C3 convertase is a normal physiologic event

The origin of autoantibody production was studied with the use of antibody to the alternative pathway C3 convertase (C3 nephritic factor (C3NeF), as a model. Pokeweed mitogen stimulation of peripheral mononuclear cells from newborn infants, normal adults, and patients with membranoproliferative glomerulonephritis indicated that the ability to make C3NeF is apparently present in everyone from the time of birth. In addition, C3NeF appeared to express a single or very limited idiotope (21/21 isolates). The data also suggest that the elaboration of C3NeF may approximate an antibody response after immunization. Thus the C3NeF fraction of the total IgG or IgM produced in culture by pokeweed mitogen-stimulated mononuclear cells from normal neonates and adults, as well as from patients, was in the range of the production of specific antibody. Further, both IgG and IgM C3NeF produced by cells from these normal individuals, including newborn infants, had an affinity for antigen (10(8) to 10(9) L/mol) that was also in the range of specific antibody. Most of the autoantibody molecules (5/7) from serum were IgG3; two B cell clones producing C3NeF were CD5-negative. These experiments indicate that unmutated germline genes are used in the production of C3NeF and that a limited spectrum of antiidiotypic antibodies regulate its production.

Production of IgG and IgM autoantibody to the alternative pathway C3 convertase in normal individuals and patients with membranoproliferative glomerulonephritis

To understand the origin of autoantibody production, we studied the ontogeny of antibody to the alternative pathway C3 convertase (C3 nephritic factor or C3NeF). Peripheral blood mononuclear cells from newborns, normal adults, and patients with membranoproliferative glomerulonephritis produced IgM and IgG C3NeF after culture for 14 days with pokeweed mitogen. Both IgM and IgG moieties appear to have the same paratope and are able to inhibit each others binding and function. The affinity constant for each of the C3NeF molecules was moderately high (10(8) liters/mol) and there appeared to be little difference between the Ka values for the IgG and the IgM autoantibodies or between Ka values for autoantibodies isolated from newborns, adults, and patients. These data, then, indicate that the ability to produce C3NeF autoantibody is present from the time of birth in normal individuals. The high affinity of these autoantibodies under normal conditions suggests that C3NeF may play a more important physiological role than previously anticipated.

On the origin of C3 nephritic factor (antibody to the alternative pathway C3 convertase): Evidence for the Adam and Eve concept of autoantibody production

The antibody to the alternative pathway C3 convertase, designated C3 nephritic factor or C3NeF, is an autoantibody that is produced in everyone from the time of birth. The elaboration of C3NeF utilizes germline V-region genes which undergo antigen-driven affinity maturation, resulting in an autoantibody that is produced in large amounts with high affinity and narrow specificity. Our data also suggest that under normal conditions, the idiotypic network may play an important part in the control of this autoantibody. Further, a defect in the network with loss of control or inappropriate stimulation may be an underlying mechanism in the unrestricted production of C3NeF in patients with membranoproliferative glomerulonephritis.

Human anti-idiotypic antibody responses to autoantibody against the alternative pathway C3 convertase

Anti-idiotypic antibodies to autoantibody against the alternative pathway C3 convertase (C3NeF) were isolated and purified from normal human serum as well as from serum from six patients with membrano-proliferative glomerulonephritis (MPGN). All preparations of anti-id antibody blocked C3NeF deposition on EC3bBb as well as C3NeF stabilization of EC3bBb functional activity. The Ka of these ant-id antibodies for C3NeF was 10(9) liters/mol which is comparable to the Ka of C3NeF for its antigen. In addition, 90% of anti-id antibody isolated from patients with MPGN and 20% isolated from normal individuals resembled Bb and bound to C3b as well as to antibody specific for the Bb portion of Factor B. These anti-id antibodies also resembled C3b and bound to antibody specific for the C3c portion of C3b. Immunization of rabbits with this latter form of anti-id antibody led to the production of functionally active C3NeF. These data indicate that C3NeF anti-idiotypic antibodies exist in two distinct forms, with and without internal imagery of C3bBb, and can occur in both normal individuals and patients with MPGN.

Nephrotic Syndrome: Increased Platelet Prostaglandin Endoperoxide Formation, Hyperaggregability, and Reduced Platelet Life Span. Reversal following Remission

Summary: Nephrotic syndrome is associated with an increased incidence of arterial and venous thrombosis. Platelet function was evaluated in 6 children with active disease (group I) and in 5 children in remission (group II). Platelet malonyldialdchyde in the presence of N-ethyl maleimide (1 mM) or thromhin (0.5 unit/ml) was used as an indicator of platelet prostaglandin endoperoxide formation in all patients evaluated, and platelet survivals were performed in 3 of 11. Platelet hyperaggregability was present in group 1 and was associated with a significant increase (P < O.001) in platelet MDA formation in the presence of either N-ethyl maleimide [4.0 ± 0.29 (1 S.D.) nmoles/109 platelets] or thrombin (1.77 ± 0.32) when compared to normal controls (3.20 ± 0.26: 1.26 ± 0.18). Other evidence for a “hypercoagulable” state included a marked reduction (P < 0.001) in plasma antithrombin III levels to 9.4 ± 3.8 mg/dl (controls, 24 ± 3) and a reduction in platelet life span in both children in whom this study was performed (half-life of 2.1 and 2.5 days), Group II patients in remission did not demonstrate platelet hyperaggregability. and platelet malonyldialdehyde was normal (3.21 ± 0.4; 1.13 ± 0.19). Antithrombin III levels were normal (26.5 ± 4.8), and platelet life-span was normal in both (iroup II children in whom this parameter was measured (half-life of 3.6 and 4.4 days). The normal half-life of 4.4 days was obtained in the same child in whom a half-life of 2.5 days was present during active disease. Platelet hyperaggregability in this syndrome appears to be due to increased prostaglandin endoperoxide synthesis. Inasmuch as a reduction in plasma antithrombin HI levels predisposes to thrombosis and a decrease in platelet survival has been documented to increase the risk of (hromboembolism in a number of pathologic states, these findings appear to be of importance in the etiology of hypercoagulability associated with nephrotic syndrome.Speculation: Platelet hyperaggregability and increased prostaglandin endoperoxide formation is seen in the nephrotic syndrome during disease activity. This platelet hyperfunctional state does not appear to be solely due to concomitant hypoalbuminemia. Other possible factors include a young, reactive platelet population with enhanced functional and thrombogenic potential or the presence of hypercholesterolemia which can he associated with platelet hyperaggregability (25).Antiplatelet aggregating agents have been used therapeutically in various disease states associated with a shortened platelet life span and an increased risk of thromboembolic complications. These agents may prove to be beneficial in decreasing the incidence of thromboembolic disease in children with the nephrotic syndrome.

Prostanoids in hemolytic uremic syndrome

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Neonatal renal arterial embolism syndrome

Attention is called to a poorly recognized syndrome of neonatal renal arterial embolism, presumably from the ductus arteriosum, resulting in malignant hypertension, congestive heart failure, respiratory distress, and increased renin secretion. Radiographic studies revealed a ductus diverticulum and multiple narrowed arteries including the lower pole branches of the right renal artery. Renal scan showed poor imaging of the lower pole of the right kidney. Nephrectomy resulted in a prompt return of the blood pressure into the normal range. Eight cases recorded in the literature resemble the one reported here, and six of the eight had an associated thrombosis of the ductus arteriosum. Our patient appears to be the first case recognized by modern techniques followed by nephrectomy and clinical cure.

Alteration of the complement system in children with Henoch Schönlein Purpura

Abstract The complement system was studied in detail in 24 patients with Henoch Schonlein Purpura. Serum levels of C3 and C3–C9 hemolytic titers were normal or elevated. Classical pathway activity was determined by quantitation of serum C1, C4, and C2 titers as well as by the ability of serum to support C3–C9 consumption with an immune precipitate and lysis of sensitized erythrocytes (CH 50 ). All of these studies were normal. Alternative pathway activity was determined by measurement of serum levels of properdin, properdin convertase, and factor B as well as the ability of serum to support C3–C9 activation with zymosan or cobra venom factor and the lysis of unsensitized rabbit erythrocytes. Only the serum levels of properdin and properdin convertase were abnormal. In 11 of 12 patients studied within the first week of the disease, levels of serum properdin (P) were reduced more than 3 SD from the normal mean; similarly, 5 of 12 patients had reduced serum levels of properdin convertase (PC). In addition, of five patients whose initial blood was obtained between the first and second week of the disease, four had low levels of either P or PC. Finally, seven samples were obtained 14 days or more after onset; four had low serum levels of P or PC and three of these were patients assayed from 1–5 years after onset. The length of time required for the P or PC to return to normal was extremely variable.

Decreased opsonic and chemotactic activities in sera of postburn patients and partial opsonic restoration with properdin and properdin convertase

Abstract Defective phagocytic functions may play a prominent role in the susceptibility of burn patients to bacterial infections. Serially collected sera from 12 patients in this study, with 1° to 3° burns of between 20 and 85% body surface, showed significantly depressed opsonic and chemotactic activities for prolonged periods. Sera from 3 of the 12 patients were assayed for C 3 , C 4 , C 3 -C 9 hemolytic activity, factor B, and properdin and properdin convertase. All factors were decreased initially, but quickly returned to normal, except properdin and properdin convertase which remained at levels of less than 50% of normal for prolonged periods. Significant restoration of yeast opsonic activity by the addition of either purified properdin or properdin convertase to opsonically deficient sera suggests that a defect of the alternate pathway of complement activation is present in patients with burns.