Primate erythrocyte-immune complex-clearing mechanism.

Previous in vitro studies have shown that immune complexes (IC) that fix complement can bind to the C3b receptor on primate erythrocytes. The in vivo function of this erythrocyte receptor, however, is unknown. This study was undertaken to determine whether the binding of IC to erythrocytes in vivo might play a role in the removal of IC from the circulation. Baboons and rhesus monkeys were prepared with a catheter in the ascending aorta to infuse IC and in the abdominal aorta, renal, hepatic, and portal veins to monitor changes in binding and clearance of IC across kidney, liver, and spleen + gut, respectively. Autologous 51Cr-labeled erythrocytes were infused intravenously and allowed to equilibrate. Preformed IC (125I-labeled bovine serum albumin [BSA] rabbit anti-BSA) were then infused into the ascending aorta at a constant rate for 120 s. Blood samples were drawn at frequent intervals for 30 min from all catheters below the IC injection site. Each blood sample was then centrifuged on percoll to separate IC bound to erythrocytes from IC in plasma or bound to buffy coat cells. This resulted in an "erythrocyte fraction" beneath the percoll that contained the IC bound to erythrocytes, and a "plasma/buffy coat fraction" above the percoll that contained the IC in plasma and IC bound to buffy coat cells. Analysis of these data showed that the majority of the IC infused into the circulation rapidly became bound to erythrocytes. However, by 5 min after beginning the IC infusion, most of this IC load had been removed from the erythrocytes as they traversed the liver. In contrast, IC on erythrocytes did not deposit in kidney. The IC-bearing erythrocytes themselves were not trapped or detained by any organ. IC in the plasma/buffy coat fraction of blood were removed from the circulation but at a relatively low rate and almost entirely by the liver. These findings suggest that primate erythrocytes intercept large complement-fixing IC in the circulation causing the IC to adhere to the erythrocyte until th e IC-bearing erythrocyte traverses liver where the IC is deposited, and the erythrocyte is returned to the circulation. This primate erythrocyte-IC-clearing mechanism may be important in the protection against diseases mediated by deposition of circulating IC.

Complement depletion accelerates the clearance of immune complexes from the circulation of primates.

Binding of immune complexes (IC) to erythrocytes in vitro is the result of interaction between C3b sites on the IC, and complement receptors type I (CRI) expressed on primate erythrocytes. Recent evidence indicates that primate erythrocytes can also rapidly bind large, preformed IC in vivo. This study was undertaken to determine if the binding of IC to baboon erythrocytes in vivo is complement dependent and to examine the effect of complement depletion on IC clearance from the circulation. The results indicate that complement depletion in vivo reduced the binding of IC to erythrocytes. There was relatively little binding of IC to leukocytes in both the complement-depleted and complement-repleted condition. Thus, the majority of IC not bound to erythrocytes remained free in the plasma and, consequently, IC infusion during the complement-depleted state resulted in increased plasma IC concentrations. This was associated with a rapid disappearance of IC from the circulation. By contrast, in the normal or complement-repleted state, a large fraction of the IC became bound to erythrocytes during IC infusion, which resulted in lower plasma IC concentrations. Under these conditions, a more gradual rate of disappearance of IC from the circulation was observed. The relatively abrupt clearance of IC from the circulation in the complement-depleted state could not be accounted for by increased hepatic or splenic uptake. These data indicate that, in contrast to previous studies in nonprimates, complement depletion in primates results in accelerated removal of IC from the circulation. This suggests that factors such as hypocomplementemia and deficient expression of erythrocyte CRI, which are known to occur in certain IC-mediated diseases, may promote IC uptake by organs vulnerable to IC-mediated injury.

Differential binding of immunoglobulin A and immunoglobulin G1 immune complexes to primate erythrocytes in vivo. Immunoglobulin A immune complexes bind less well to erythrocytes and are preferentially deposited in glomeruli.

Primate erythrocytes appear to play a role in the clearance of potentially pathogenic immune complexes (IC) from the circulation. This study was undertaken to compare the clearance from the circulation and tissue uptake of two monoclonal IC probes: one of which, IgG1-IC, was bound well by erythrocytes, the other of which, IgA-IC, was bound relatively poorly by erythrocytes. The IC probes were labeled with different iodine isotopes and infused either concomitantly or sequentially into the arterial circulation. The results indicate that, compared with IgG1-IC, IgA-IC bind less well to primate erythrocytes, are cleared from the circulation more quickly despite their smaller size, and show increased uptake in kidney and lung but decreased uptake in liver and spleen. Evidence is presented which suggests that this pattern of clearance from the circulation and systemic uptake of IgA-IC is the result of decreased binding of IgA-IC to circulating erythrocytes. These findings support the hypothesis that the primate erythrocyte-IC clearing mechanism may be critically important for the safe removal of IC from the circulation.

Acute massive (pericardial effusive) pulmonary thromboembolism--pulmonary embolectomy revisited.

The most recent patient in a 13-year experience with 14 patients suffering massive pulmonary thromboembolism requiring pulmonary thromboembolectomy is the focus of this report. This 40-year-old woman not only survived life-threatening acute hypoxemia and right heart failure, but was also found to have developed a unique transudative 700 cc pericardial effusion. Pulmonary artery pressure was 90/30 (mean 50 mmHg), accompanied by 17 mm right ventricular alternans. Systemic alternans and tamponade physiology were absent. This unusual natural model for acute right heart failure illustrates a novel mechanism for pericardial effusion physiology.

Immune complex erythrocyte complement receptor interactions in vivo during induction of glomerulonephritis in nonhuman primates.

Multiple lines of evidence indicate that the erythrocyte complement receptor (E-CR) system, which is unique to the primate, may play an important role in the clearing of immune complexes (ICs) from the circulation. However, all previous investigations of IC/E-CR interactions in vivo have involved the study of small amounts of preformed or passively formed ICs interacting with E-CR that were numerically in vast excess. The present study was undertaken to assess IC/E-CR interactions under conditions in which large amounts of ICs were formed in the circulation, amounts that when sustained for several weeks by daily intravenous administration of antigen resulted in the development of active glomerulonephritis. Twelve cynomolgus monkeys with E-CR levels ranging from 25 to 5000 mean CRs per erythrocyte (CR/E) were actively immunized to BGG, and 6 to 12 weeks later they were studied first at low levels of IC formation in vivo (L-Protocol experiments, mean 125I-labeled BGG dose of 0.04 mg/kg given over 1 minute, a marked antibody excess state) and then at high levels of IC formation in vivo (H-Protocol experiments, mean 125I-labeled BGG dose 4.9 mg/kg given over 10 minutes, a state approximating antigen-antibody equivalence). Cynomolgus monkeys with fewer than 100 CR/E showed no evidence of binding of ICs to erythrocytes with either low-dose or high-dose 125I-labeled BGG. However, cynomolgus monkeys with greater than 450 CR/E showed significant binding of ICs to erythrocytes: mean peak binding of 125I-labeled BGG to erythrocytes was 22.1% +/- 1.1% in the L-Protocol experiments and 33.4% +/- 8.0% in the H-Protocol experiments. During H-Protocol experiments, mean CR/E, measured by using a monoclonal anti-human CR1 antibody, decreased acutely (mean decrease 36.2% +/- 14.1%, p less than 0.05), with recovery of E-CR levels within the next 24 to 72 hours. The acute decrease in E-CR levels could not be accounted for by occupancy of E-CR by ICs or by change in hematocrit. In summary, the present study demonstrates that during the development of glomerulonephritis, IC/E-CR interactions occur and the E-CR system is altered by these interactions. The present observations are consistent with the hypothesis that the E-CR system may play a role in the pathogenesis of IC-mediated disease in the primate.

Renal artery pressure gradients in patients with angiographic evidence of atherosclerotic renal artery stenosis.

From October 1979 to August 1991, 231 patients underwent renal artery balloon angioplasty at The Ohio State University Hospitals. Atherosclerotic renal vascular disease was present in 171 of these patients. From this cohort, 138 patients undergoing their first angioplasty had renal artery pressure gradients performed before and after renal artery angioplasty. The demographics of this group included age 66.9 +/- 10 years (+/- SD), male 51%, white 94%, black 6%, diabetes mellitus 28%, systolic blood pressure 157 +/- 26 mm Hg, diastolic blood pressure 86 +/- 13 mm Hg, standard daily doses of antihypertensive medications 4.2 +/- 3, and serum creatinine 2.6 +/- 2.3 mg/dL. Plasma renin activity was measured in 25 patients and was shown to be elevated in 16. The renal artery stenoses were main renal artery 75%, orificial 22%, distal renal artery 1.4%, and combinations of the above 2.2%. Solitary kidneys were present in six patients (4.3%). Bilateral renal artery stenosis was present in 45% of patients and bilateral angioplasties were performed in one third of these patients. The preangioplasty systolic blood pressure gradient was 109 +/- 50 mm Hg (range, 20 to 230 mm Hg) and the postangioplasty renal artery pressure gradient was 12 +/- 16 mm Hg (range, 0 to 78 mm Hg) (P < 0.001). There were no complications related to measurement of the pressure gradients. The magnitude of the renal artery pressure gradients did not correlate with blood pressure level, number of antihypertensive medications, or serum creatinine level.(ABSTRACT TRUNCATED AT 250 WORDS)