Mats Heideman

Anaphylatoxin generation in multisystem organ failure

Complement components were studied in 44 patients with extensive injuries or infections. The concentrations of anaphylatoxins (C4a, C3a, and C5a) and other complement components (C1INH, C4, C3, and C5) were determined in plasma using radioimmunoassay and rocket immunoelectrophoresis techniques. The results were correlated with the development of multisystem organ failure (MSOF). In particular, plasma concentrations of C3a and C4a were found elevated in trauma patients. These elevated anaphylatoxin levels were correlated with severity of the injury. As reported in other types of patients, the apparent C5a plasma levels were not elevated. Therapy reduced the plasma levels of C3a with great predictability. It appears that plasma C3a and C4a levels may relate not only to severity of the injury but may signal onset of secondary events such as bacteremia. Consequently, longitudinal monitoring of anaphylatoxin levels may prove helpful in diagnosing the status of trauma patients.

Complement activation and hematologic, hemodynamic, and respiratory reactions early after soft-tissue injury.

The effect of soft-tissue trauma was studied in dogs. Following injuries to the hind leg an aggregation of thrombocytes in blood and trapping in the lung was noted. Injury was initially followed by leukopenia and later by leukocytosis. Early hemolysis of red cells was observed. The injury was accompanied by complement activation. Its possible relation to hemolysis, leukopenia, thrombocytopenia, and increased insufflation pressure is discussed.

Complement activation and reinfusion of wound drainage blood

Eighteen patients undergoing total hip replacement (n = 13) or knee arthroplasty (n = 5) due to osteoarthritis or osteoarthrosis were prospectively studied in an investigation of complement activation and anaphylatoxin release in association with reinfusion of aspirated wound blood. Twelve of the patients needed blood transfusions and received an average of 390 +/- 75 ml (+/- SD) of autologous blood within 45 min. Plasma complement components, anaphylatoxins, and inhibitors were studied 1 min before and 15 min after the start of and 15 min after the completion of autologous transfusion. Samples also were taken from the collected blood, before and after passing it through a microporous filter. Blood gases and systemic complement samples were drawn simultaneously. There were no significant changes in systemic complement variables before, during, or after transfusion of autologous blood. However, in the aspirated blood, increased concentration of anaphylatoxins (C3a and C5a) and terminal complement complexes (TCC) were present (P less than 0.001). There were no differences observed between samples drawn before and after filtration of the blood. The concentration of C5 was less in the collected blood than in the systemic blood (P less than 0.05). No changes in blood gases were observed. This study demonstrated that postoperatively salvaged whole blood underwent anaphylatoxin formation and complement activation. However, after reinfusion of this blood, neither systemic complement activation nor clinical complications were observed.

Effect of Nonviable Tissue and Abscesses on Complement Depletion and the Development of Bacteremia

Complement concentrations and blood cultures were compared in 58 patients within 24 hours of injury and weekly thereafter. Extensive amounts of nonviable tissue (n = 40) were associated with a mean depletion of C4, C3, and C5 by 56%, and minor injuries (n = 18) by 22% of normal concentration within 14 hours after injury. The C4, C3, and C5 concentrations returned to normal or above within a week after minor injuries, but not following major injuries. However, C4, c3, and C5 levels remained depressed after major injuries unless necrotic tissue was removed or abscesses were drained. If complement concentration was below 50% of normal for more than a week all patients developed bacteremia. Following debridement or drainage complement returned to normal in 11 patients and blood cultures became negative in seven. Possible consequences by activation and altered availability of complement for chemotaxis, opsonization, and lysis of bacteria have been analyzed and related to the development of bacteremia.

Altered anaphylatoxin activity during induced hypoperfusion in acute and elective abdominal aortic surgery.

Fifty patients operated on for abdominal aortic aneurysms, ten acutely for ruptured aneurysms and 40 electively, were studied. The anaphylatoxins (C3a and C5a) and the activity of their inhibitor were determined preoperatively, regularly per-, and postoperatively. Increased anaphylatoxin activity was accompanied by altered airway pressure, central hemodynamics, and pulmonary, hepatic, and renal functions. During aortic clamping the anaphylatoxins increased and the activity of their inhibitor decreased. During the clamping period airway pressure, pulmonary artery pressure, and pulmonary vascular resistance increased. These respiratory and hemodynamic changes might partly be explained as biologic effects of anaphylatoxins. The plasma C3a increase correlated with the duration of aortic clamping. Patients with prolonged anaphylatoxin increase were prone to develop multisystem organ failure. Anaphylatoxins released during induced hypoperfusion could be one of the factors influencing respiratory and hemodynamic changes in patients operated on for aortic abdominal aneurysms.

The effect of thermal injury on hemodynamic, respiratory, and hematologic variables in relation to complement activation

The effects of thermal injury on circulation, respiration, and complement activity was studied in dogs. An aggregation of platelets in the blood and trapping in the lung were observed following burn injury. Leukopenia appeared first, then leukocytosis. Hemolysis of red cells corresponding to a destruction of about 30% of the erythrocytes was observed. A blood pressure decrease and a tracheal insufflation pressure increase followed thermal injury. Blood gas and lactate changes like those seen during a low perfusion state were recorded, but signs of impaired oxygenation of arterial blood were also observed. A possible mechanism by which denatured proteins might initiate some of the symptoms seen after thermal injury is suggested and its relation to complement activation is evaluated.

IgG binding to cytoskeletal intermediate filaments activates the complement cascade.

The cellular plasma membrane becomes permeable to macromolecules during the cell injury process. This results in exposure of the interior of the cell to plasma proteins and to high-affinity binding of the Fc part of IgG to intermediate filaments (Hansson, G K, Starkebaum, G A, Benditt, E P & Schwartz, S M, Proc natl acad sci USA 81 (1984) 3103). Such IgG binding could be an early step in a process that serves to eliminate the injured cell. We have now identified its effect on the complement system. Intermediate filaments were reconstituted in vitro from purified vimentin, and incubated with plasma proteins. Cross-linker experiments showed binding of the heavy chain of IgG to vimentin, indicating that the vimentin protein carries an Fc-binding site. In contrast, no direct binding of complement factor Clq to vimentin could be detected. Binding of both IgG and Clq could, however, be detected by immunofluorescence when cytoskeletons of cultured endothelial cells were incubated with fresh serum. Therefore, IgG binding to filaments in the presence of serum is accompanied by Clq binding to IgG. This was in turn followed by fixation of C4 and C3 to intermediate filaments in a process that was dependent on both Ca2+, Mg2+ and Clq, indicating that it was part of a complement activation via the classical pathway. Exposure of fresh serum to intermediate filaments also resulted in production of the anaphylatoxic complement cleavage fragment. C3a, with a dose-response relationship between the amount of filaments present and the amount of C3a generated. Chemotactic activity towards granulocytes and monocytes was also generated by exposure of serum to intermediate filaments, and this activity was dependent on the presence of complement factor C5 and on the classical complement activation cascade, implying that it was due to the C5a peptide. Exposure of the interior of the cell to plasma proteins thus results in binding of IgG to intermediate filaments and activation of the complement cascade via the classical pathway. This, in turn generates bioactive mediators which may recruit leukocytes to the injured cell (C5a) and have profound effects on vascular permeability (C3a, C5a). We propose that this is part of a scavenger mechanism for the elimination of damaged cells.

Complement activation early in endotoxin shock

The effect of endotoxin infusion was studied in dogs. Aggregation of platelets in the blood and trapping in the lung were observed. Endotoxin infusion was initially followed by leucopenia. Hemolysis of red cells corresponding to about 1% of the erythrocytes was observed. A blood pressure decrease and a tracheal insufflation pressure increase followed injury. Impaired oxygenation of arterial blood was registered. The infusion was accompanied by complement activation. Its relation to the phenomena studied is discussed.

Anaphylatoxin generation in acute pancreatitis

Fifty-one patients with elevated serum amylase and clinical signs of acute pancreatitis were studied prospectively. The concentrations of anaphylatoxins (C3a and C5a) were measured with a radioimmunoassay and the activity of their inactivator was determined. The pancreatitis was classified as mild, moderate, or severe according to Ransons 11 signs, appearance of peritoneal fluid, and development of multisystem organ failure (MSOF). Plasma C3a and C5a concentrations were elevated during attacks of acute pancreatitis. Anaphylatoxin levels correlated with the severity of the disease (C3a, P less than 0.001; C5a, P less than 0.05). The highest and most persistent levels were found in the group with MSOF. C3a levels decreased rapidly during recovery. In patients with complications like abscess or pseudocyst, the C3a elevation persisted until adequate treatment was instituted. In this study, no significant changes of the inactivator levels were found, except at discharge when the inactivator level of the severe group was elevated compared to that of the moderate and mild groups (P less than 0.05).

Inhibition of complement activation by high-dose corticosteroids in total hip arthroplasty

Anaphylatoxins are released during total hip arthroplasties (THA) when methylmethacrylate is used. These toxins may be responsible for hemodynamic and pulmonary instability during surgery. Recent studies have shown that the release of anaphylatoxins may be inhibited by high-dose corticosteroids (HDC). In a double-blind study 30 consecutive patients with osteoarthritis or failed hip fractures were randomized into two groups; 15 patients received HDC at the beginning of the operation and 15 patients, designated the control group, received infused saline. Anaphylatoxin formation, arterial oxygen tension, and blood pressure were determined preoperatively, during the operation, and one day postoperatively. The patients who received HDC had no significant alteration regarding the anaphylatoxins or arterial oxygen tension during surgery. However, in the control group elevated C3a levels and decreased PaO2 levels were found. Corticosteroids therefore inhibit complement activation and anaphylatoxin release in hip arthroplasty surgery.