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

Neutrophil granulocyte functions in severely burned patients

Burns wound sepsis is not only the most common but also the most severe complication following extensive thermal injury. One conceivable explanation of this problem is a reduced capacity of the polymorphonuclear neutrophil leucocytes of these patients to combat the invading microbes. Fifty patients (42 male and 8 female) with deep dermal burns, covering 20-90 per cent of the total body surface area, were investigated from immediately after the injury until death or until healing of the wounds. The following functions of the neutrophil granulocytes were studied: chemotaxis and random migration utilizing a modified Boyden chamber technique, phagocytosis of Staph. aureus and IgG-coated latex particles, bactericidal capacity, e.g. killing of Staph. aureus and the neutrophil granulocyte content of: myeloperoxidase, lactoferrin, and chymotrypsin-like cationic protein. The presence of stimulators and inhibitors of the granulocyte functions was studied using gel filtration of the patient's serum on Sephacryl gel columns. Sera from all patients obtained within the first 1-3 days post-burn contained significantly increased amounts of heat-labile chemokinetic stimulating activity. Sera obtained between days 4 and 10 after injury contained significantly decreased amounts of heat-stable chemokinetic stimulating activity. Reduced chemokinetic activity was found during the third and fourth weeks following major burns (greater than or equal to 40 per cent) due to the presence of one or both heat-stable chemokinetic inhibitory activities. During the second week post-burn patients with burns larger than 40 per cent of the body surface area who showed an inhibition of chemotaxis, also had defects in phagocytosis, and often impaired bactericidal capacity concomitant with lower contents than normal of the granular enzymes. A hyaluronic acid preparation in low concentrations was found to counteract the migration inhibitory effect demonstrated in vitro in sera from patients with severe burns. Based upon these results a series of patients with severe burns and impaired functions of the neutrophil granulocytes have been treated with small amounts of this hyaluronic acid preparation subcutaneously. Very promising results have been noticed, similar to those found in vitro.

Infections in burn patients: a paradigm for cutaneous infection in the patient at risk

The burn patient is in many ways the archetypical immunosuppressed host: the anatomic barriers have been breached and the host's defenses suppressed. Infection is the leading cause of death in hospitalized burn patients not having inhalation injury, being responsible for between 50 and 75 percent of the hospital deaths. Burn injury produces profound abnormalities in immunologic function. These changes are generally proportional to the degree of burn injury (surface area and depth). Cell-mediated immune function is suppressed. Anergy and depressed allograft rejection occur. Acute burn serum samples contain several factors that suppress cell-mediated immune functions. Antibody levels are usually mildly to moderately reduced. Complement, particularly the alternative complement pathway, may be massively activated and depleted, removing a critical defense mechanism against gram-negative rod infections for which preformed antibodies are absent. This depression is further exacerbated by malnutrition and infection. Fibronectin levels are also reduced. Phagocytic cell function is abnormal with burns. Neutrophil numbers may be depressed, and function is abnormal. Chemotactic responsiveness, cytoplasmic granule enzyme content, and oxygen radical generation are abnormal. Monocyte/macrophage dysfunction has similarly been demonstrated. Burn infections reflect abnormal host functions as well as changes in the hospital environment and microbial selection pressures. The burn patient is a model of cutaneous infection in the patient at risk.

Development and application of an enzyme-linked immunosorbent assay for the quantitation of alternative complement pathway activation in human serum

We have developed a new, specific, and highly sensitive enzyme-linked immunosorbent assay (ELISA) which quantitates activation of the alternative pathway in human serum, plasma, or on the surface of activators. The ELISA detects the third component of complement (C3b), proteolytic fragment of complement Factor B (Bb), and properdin (P) complex or its derivative product, C3b,P. In the method, activator-plasma mixtures, plasma containing an activated alternative pathway, or other samples are added to the wells of microtitration plates precoated with antibody to P. C3b, Bb,P or C3b,P complexes which become bound are quantitated by subsequently added, enzyme-labeled, anti-C3. The resulting hydrolysis of the chromogenic substrate is expressed as nanograms of C3b by reference to a C3 standard curve. In addition to absolute specificity for activation of the pathway because of the nature of the complex detected by the assay, the ELISA is highly sensitive and able to reproducibly detect 10-20 ng/ml of C3b,P complexes in serum. This value corresponds to 0.0015% of the C3 in serum. In a series of studies to validate the parameters of the ELISA, reactivity was found to be dependent on the presence of alternative pathway proteins, the functional integrity of the pathway, and on the presence of magnesium. Sheep erythrocytes were converted to activators by treatment with neuraminidase. By using a variety of activators, the kinetics of activation and the numbers of bound C3b molecules quantitated by the ELISA were very similar to those measured by C3b deposition. The ELISA also detected identical activation kinetics when MgEGTA-serum and a mixture of the purified alternative pathway proteins were used as sources of the pathway. ELISA reaction kinetics also correlated with the restriction index, a measure of alternative pathway-activating ability. These studies cumulatively validate the ELISA as a direct and quantitative assay for alternative pathway activation. The sensitivity of the ELISA has permitted its use to detect direct alternative pathway activation by several viruses. The ELISA has also shown that certain classical pathway activators trigger the amplification loop of the alternative pathway while others do not. In addition, stable ELISA reactive complexes appeared in the supernatant of mixtures of serum with certain, but not other activators. The ability of the ELISA to detect activation which has already occurred and the stability of the reactive complexes permits studies of clinical sera. Normal human sera (20) contained low levels (5-20 ng/ml) of ELISA-reactive complexes. A proportion of sera from individuals with the adult respiratory distress syndrome (9-10), typhoid fever (8-10), malaria (3-5), gram-negative sepsis (9 of 47), acute trauma and shock (6 f 25), and systemic lupus erythematosus (3 of 29) showed elevated levels of complexes reactive in the alternative pathway ELISA. In contrast, nine sera from patients with circulating C3 nephritic factor were not reactive in the ELISA.

Preferential activation and depletion of the alternative complement pathway by burn injury

Complement levels of eight adult burn patients (25% to 90% body surface area) were studied upon admission to a burn unit and sequentially for one week. Mean classical pathway titers (CH50) were 49% below the normal mean, while hemolytic C4 titers were reduced by 53% and C3 by 43%. However, the alternative pathway titer was reduced by more than 90%, suggesting preferential depletion of this pathway. This depletion was associated with sepsis, pneumonia, and "shock lung." Alternative pathway deficiency was still present one week postburn, and may contribute to the susceptibility of burn patients to bacterial sepsis.

Alternative complement pathway activation increases mortality in a model of burn injury in mice

We have studied the role of the complement system in burn injury in an experimental model in mice. A 25% body surface area, full-thickness scald wound was produced in anesthetized animals. Massive activation of the alternative complement pathway, but not the classical pathway, was seen. This activation was associated with the generation of neutrophil aggregating activity in the plasma, neutrophil aggregates in the lungs, increased pulmonary vascular permeability, and increased lung edema formation. Decomplementation with cobra venom factor (CVF) or genetic C5 deficiency diminished these pathologic changes, and CVF pretreatment substantially reduced burn mortality in the first 24 h. Preliminary data show that human burn patients have a similar pattern of complement activation involving predominantly the alternative pathway, indicating the possible relevance of the murine model to human disease.

Influence of hip arthroplasty upon chemotactic behaviour of leucocytes

Fourteen patients treated with total hip endoprosthesis were investigated for leucocyte defects. A chemotactic assay was used as an indicator of leucocyte function. Tests were carried out preoperatively and on postoperative days 1, 3 and 6. The chemotactic index started to decline on the first postoperative day, reached a peak on the third day after surgery and returned to almost preoperative values on the sixth day. The results might provide a clinical explanation for the data showing a high postoperative infection rate in total hip surgery.

Serum-mediated inhibition of polymorphonuclear leukocyte function following burn injury

Serial serum samples from 12 bacteremic burned patients were tested at a physiologic concentration for their ability to facilitate phagocytosis and intracellular killing of the homologous infecting Staphylococcus aureus strains by normal human polymorphonuclear leukocytes in comparison to pooled normal human serum. Serum-mediated inhibition of leukocyte bactericidal activity was demonstrated in three of the patients during 13 to 56 days after burn. Decreased bacterial activity was related to an inhibitory effect of the burn sera on the phagocytic process, which reduced the number of internalized bacteria available for intracellular killing. The serum-mediated inhibition of phagocytosis was not found to be dependent on bacterial surface properties unique to S. aureus. The inhibitory effect was shown to involve a direct interaction of the burn sera with the leukocytes, which was not associated with cell death and was not reversed by washing of the leukocytes.