Abstract
Increased levels of interleukin 8 (IL-8) are found in bronchoalveolar lavage (BAL) fluids from patients with the acute respiratory distress syndrome (ARDS). However, IL-8 is not an efficient predictor of the course of ARDS. Our prior studies demonstrated that IL-8 present in lung fluids from patients with ARDS is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 complexes). These data led us to hypothesize that the complexes might better predict the development of acute lung injury. Accordingly, we measured concentrations of free and complexed IL-8 in BAL fluids from 19 patients at risk and 45 with established ARDS on Days 1, 3, 7, 14, and 21 after the onset of ARDS. The concentrations of anti-IL-8:IL-8 complexes in patients with ARDS on Day 1 were significantly higher than in patients at risk (p < 0.05). There was a significant association between anti-IL-8:IL-8 complex concentrations and the onset of ARDS (p = 0.03). Similarly, anti-IL-8:IL-8 complex concentrations were significantly higher in patients on Day 1 of ARDS who later died (p < 0.05), and the association between high anti-IL-8: IL-8 complex concentrations and the probability of dying was significant (p = 0.03). The presence of anti-IL-8:IL-8 complexes in BAL fluids of patients with ARDS is an important prognostic indicator for the development and outcome of ARDS.
Acute respiratory distress syndrome (ARDS) is a complex clinical syndrome characterized by a diffuse acute lung injury (1), and a significant increase in both the total number of neutrophils (PMNs) and the proportion of PMNs occurring in the alveolar spaces. For example, PMNs constitute 70–80% of the cells in bronchoalveolar lavage (BAL) fluid from patients with ARDS as compared with approximately 0.8–3% in normal subjects (2, 3). Activated PMNs that release metalloproteinases, myeloperoxidase, collagenases, and reactive oxygen species during migration into alveolar spaces may contribute to the endothelial and epithelial injury that is characteristic of ARDS (2, 4). IL-8, a potent neutrophil attractant and activator, has been implicated in the PMN recruitment in lungs of patients with ARDS (5, 6).
The increase in endothelial and epithelial permeability that occurs in ARDS allows higher molecular weight proteins, such as IgG and IgM, to enter the airspaces (4). Previous studies have shown that a significant portion of IL-8 in lung fluids from patients with ARDS is associated with anti-IL-8 autoantibodies (7). Autoantibodies against IL-8 have been found in human plasma, which contains anti-IL-8 IgG as well as IgG:IL-8 complexes (8), and in gastric mucosa where IgA binds IL-8 (9). Anti-IL-8 autoantibodies may be involved in the pathogenesis of human diseases (9). Our earlier findings raised the possibility that autoantibodies to IL-8 may modulate IL-8 function in the lungs by neutralizing its biological activity (7).
The goal of this study was to investigate the relationship between anti-IL-8:IL-8 complexes in BAL fluid and the onset and severity of ARDS. We compared the concentrations of free and complexed IL-8 in BAL fluids from 19 patients at risk for ARDS and 45 with established ARDS who were studied on Days 1, 3, 7, 14, and 21 after the onset of ARDS. We examined the relationship between free and complexed IL-8 and the clinical course of these patients.
All studies involving human lung fluids were approved by the Human Subjects Review Committees of the University of Washington Medical Center (Seattle, WA) and the University of Texas Health Center at Tyler. Informed written consent was obtained from all the subjects or their representatives.
BAL fluids from 19 patients at risk for ARDS and 45 with established ARDS (1, 3, 7, 14 and 21 d after the onset of ARDS) were collected as previously described (10). Cell-free BAL fluid specimens were aliquoted and stored at −80° C until analyzed. (The samples were frozen approximately 30 min after the bronchoscopy procedure.) All assays were done at the same time on defrosted samples. Ventilatory strategies were similar in all patients. Patients at risk for ARDS met predefined criteria for either sepsis or severe trauma (11). Patients with ARDS met the following criteria: (1) a PaO2 /Fi O2 ratio ⩽ 150 mm Hg, or ⩽ 200 mm Hg with ⩾ 5 cm H2O positive end-expiratory pressure; (2) diffuse parenchymal infiltrates in at least three of four quadrants on chest X-ray; and (3) a pulmonary artery wedge pressure of ⩽ 18 mm Hg and/or no clinical evidence of congestive heart failure. A modified lung injury score (LIS) was used to quantitate the clinical severity of ARDS (10-12). Survival was defined as discharge from the hospital.
Total white cell numbers were assessed with a hemacytometer. Cytocentrifuge preparations of each sample were made and stained with the Diff-Quik stain (American Scientific Products, McPark, IL), and a differential cell count was performed on each slide.
IL-8 concentration was measured in an enzyme-linked immunosorbent assay (ELISA), using a matched antibody pair according to the manufacturer protocol (R&D Systems, Minneapolis, MN).
Free anti-IL-8 autoantibody, and anti-IL-8:IL-8 complexes, were measured in an ELISA as previously described (7).
The total protein concentration in the samples was measured with Coomassie Plus protein assay reagent (Pierce, Rockford, IL) according to the manufacturer instructions, with bovine serum albumin as the standard (Sigma, St. Louis, MO).
Differences between groups were analyzed by a simple one-way analysis of variance (ANOVA), or if the data were not normally distributed, by a Kruskal–Wallis ANOVA on ranks. All multiple comparison tests were two-tailed. Direct comparisons between two treatment groups were performed with the unpaired Student t test, or the nonparametric Mann–Whitney test when the data sets were not normally distributed. Correlations between the IL-8 or anti-IL-8:IL-8 complexes and neutrophil concentrations were determined by a Spearman rank order correlation method (the residuals or distances of the data points from the regression line were not normally distributed). Polynomial regression was used to test the relationship between LIS and concentrations of anti-IL-8:IL-8 complexes. Logistic regression was used to estimate the effect of anti-IL-8:IL-8 complexes on the development of ARDS and the risk of death. A p value of 0.05 or less was considered significant. All statistical analyzes were performed with SigmaStat (SPSS Science, Chicago, IL).
Nineteen patients at risk for ARDS were studied (Table 1). Lung lavage samples were collected 1, 3, and 5–7 d after the onset of risk. Of the 19 patients, 14 had lavages on two of the study days, and 7 had lavages on all three study days. The mortality was 10%, and six of these patients later developed ARDS. BAL was also performed on 45 patients with ARDS at Days 1, 3, 7, 14, and 21 after the onset of ARDS (Table 1). Each patient had all subsequent studies, unless they were extubated or died. The mortality of the ARDS cohort was 20%.
| Characteristic | At Risk | ARDS | ||
|---|---|---|---|---|
| n | 19 | 45 | ||
| Risk for ARDS | ||||
| Trauma | 63% | 38% | ||
| Sepsis | 37% | 33% | ||
| Other* | 0% | 29% | ||
| Age, yr | ||||
| Mean | 46 | 45 | ||
| Range | 25–75 | 18–75 | ||
| Sex | ||||
| % Male | 55 | 62 | ||
| Hospital mortality, %† | 10 | 20 | ||
| LIS‡ | 1.80 ± 0.84 | 2.55 ± 0.70 |
The BAL fluid total protein concentration and PMN numbers did not differ significantly among the groups of patients at risk for ARDS (Kruskal–Wallis ANOVA on ranks; Table 2). The concentrations were similar for patients who developed ARDS and those who did not (t test [protein], Mann–Whitney test [PMN], Table 2). Patients at risk (who developed ARDS and those who did not) had significantly lower concentrations of total protein and PMN than did patients with ARDS on Day 1 (p < 0.05, Mann–Whitney test; Tables 2 and 3). In patients with ARDS (Table 3), survivors and nonsurvivors had comparable initial total protein and PMN concentrations (Mann–Whitney test). The total protein and PMN concentrations declined with time in survivors (p < 0.05, Kruskal–Wallis ANOVA on ranks; Table 3), whereas in nonsurvivors, declines in total protein (ANOVA) and PMN concentrations were not significant (Kruskal–Wallis ANOVA on ranks).
| Total Protein (μg/ml ) | PMN (×104 ) | IL-8 (pg/ml ) | Anti-IL-8:IL-8 (ng/ml ) | |||||
|---|---|---|---|---|---|---|---|---|
| Day 1 | ||||||||
| ARDS (n = 6) | 80.9 (40.0–1,334.3) | 1.6 (0.5–32.0) | 354.5 (65.4–531.5) | 0.1 (0.0–1.2) | ||||
| No ARDS (n = 13) | 329.0 (54.7–455.9) | 3.8 (0.4–7.6) | 301.5 (85.5–524.5) | 0.3 (0.0–1.2) | ||||
| Day 3 | ||||||||
| ARDS (n = 5) | 534.3 (103.3–720.9) | 2.0 (1.4–8.3) | 85.8 (78.8–491.5) | 0.6 (0.0–2.0) | ||||
| No ARDS (n = 9) | 137.0 (81.8–328.0) | 2.0 (0.3–16.3) | 132.1 (70.1–207.5) | 0.2 (0.1–0.3) | ||||
| Days 5–7 | ||||||||
| No ARDS (n = 8) | 71.1 (17.9–260.4) | 3.9 (0.4–9.1) | 303.1 (51.0–1221.9) | 0.2 (0.0–0.6) |
| Total Protein (μg/ml ) | PMN (×104 ) | IL-8 (pg/ml ) | Anti-IL-8:IL-8 (ng/ml ) | |||||
|---|---|---|---|---|---|---|---|---|
| Survivors | ||||||||
| Day 1 (n = 30) | 469.6†(265.4–1,215.1) | 36.0†(11.0–69.0) | 427.4 (154.9–748.9) | 0.9‡(0.4–2.1) | ||||
| Day 3 (n = 36) | 353.2§(156.0–524.4) | 28.0§(9.3–78.0) | 326.4 (114.4–665.8) | 0.4 (0.1–1.1) | ||||
| Day 7 (n = 29) | 127.6†,§ (67.6–220.6) | 3.7†,§(0.9–8.0) | 176.2 (49.2–426.4) | 0.2‡ (0.0–0.4) | ||||
| Day 14 (n = 15) | 81.9§(26.1–199.9) | 2.4†,§(0.6–7.6) | 118.4 (28.1–444.1) | 0.1 (0.0–2.1) | ||||
| Day 21 (n = 11) | 93.8†,§(69.4–122.5) | 3.7†,§(1.1–13.0) | 169.6 (86.3–415.5) | 0.3 (0.1–0.9) | ||||
| Nonsurvivors | ||||||||
| Day 1 (n = 9) | 505.5 (189.1–1,232.3) | 49.0 (14.0–92.0) | 380.2 (252.9–1,120.2) | 2.0 (0.3–3.4) | ||||
| Day 3 (n = 9) | 260.4 (188.8–479.6) | 22.0 (4.8–69.0) | 268.9 (157.3–563.6) | 0.3 (0.2–0.9) | ||||
| Day 7 (n = 4) | 197.9 (91.3–1,060.0) | 24.0 (9.6–102.0) | 209.7 (57.4–137,002.0) | 2.8 (0.6–9.1) | ||||
The LIS was significantly lower (p < 0.05, t test) in patients at risk for ARDS than in patients with ARDS (Day 1) (mean LIS, 1.80 ± 0.84 versus 2.67 ± 0.54) (Table 1). In addition, the LIS tended to decline in patients with sustained ARDS, and was significantly lower on Day 21 of ARDS than on Day 1 (p < 0.05, Kruskal–Wallis ANOVA on ranks; Table 1).
Patients at risk for ARDS. IL-8 and anti-IL-8:IL-8 complexes were detectable in the lungs on Day 1 of risk, within 24 h of the time the clinical risk was identified. The median IL-8 concentration remained elevated in patients who were at risk for ARDS (Figure 1). In addition, the initial IL-8 concentration did not separate patients who did or did not progress to ARDS (Mann–Whitney test and t test; Table 2). This was also true when IL-8 was normalized for total protein (IL-8/protein ratio) (Mann–Whitney test and t test, data not shown).
Fig. 1. Serial concentrations of IL-8 in BAL fluids collected from patients at risk for ARDS (Days 1, 3, and 5–7), and patients with ARDS (Days 1, 3, 7, 14, and 21).
[More] [Minimize]Anti-IL-8:IL-8 complexes were detectable at all times in patients who remained at risk for ARDS. The anti-IL-8:IL-8 complex concentrations also did not distinguish the patients who did or did not progress to ARDS (Mann–Whitney test; Table 2).
Patients with established ARDS. The concentrations of IL-8 and anti-IL-8:IL-8 complexes were high in BAL fluids at the onset of ARDS (Table 3). There was no significant difference between IL-8 concentrations at the beginning of ARDS and the onset of risk for ARDS (Mann–Whitney test; Figure 1). The concentrations of IL-8 at the onset of ARDS did not separate the patients who lived or died (Mann–Whitney test, Table 3), even when expressed as the IL-8/total protein ratios (Mann–Whitney test) (data not shown). The IL-8 concentration tended to decline with time in survivors (p = 0.07, Kruskal– Wallis ANOVA on ranks) but not in nonsurvivors (p = 0.57, Kruskal–Wallis ANOVA on ranks). It should be noted that when serial data points of individual patients were analyzed changes in IL-8 and anti-IL-8:IL-8 complex concentrations mirrored those presented in Figures 1 and 2, and Tables 2 and 3 (data not shown).
Fig. 2. Serial concentrations of anti-IL-8:IL-8 complex in BAL fluids collected from patients at risk for ARDS (Days 1, 3, and 5–7), and patients with ARDS (Days 1, 3, 7, 14, and 21).
[More] [Minimize]Anti-IL-8:IL-8 complex concentrations were significantly higher in BAL fluids at the beginning of ARDS than in patients at the onset of risk for ARDS (p < 0.05, Mann–Whitney test) (Tables 2 and 3 and Figure 2). This was also true when anti-IL-8:IL-8 complex concentration was normalized for total protein concentration (p < 0.05, Mann–Whitney test; Figure 3). The initial anti-IL-8:IL-8 complex concentrations tended to be higher in patients with ARDS who died (p = 0.08, Mann– Whitney test; Table 3). This became significant when expressed as anti-IL-8:IL-8/total protein ratio (p < 0.05, Mann– Whitney test; Figure 4). The anti-IL-8:IL-8 complex concentrations declined significantly with time in the survivors (from Day 1 of ARDS to Day 7) (p < 0.05) but not in patients who died (p = 0.25, Kruskal–Wallis ANOVA on ranks; Table 3).
Fig. 3. Elevated ratios of anti-IL-8:IL-8 complex concentrations to total protein concentrations in BAL fluids of patients with ARDS on Day 1. Comparison with patients at risk for ARDS (p < 0.05, Mann–Whitney test).
[More] [Minimize]
Fig. 4. Elevated ratios of anti-IL-8:IL-8 complex concentrations to total protein concentrations in BAL fluids collected from nonsurvivors on Day 1 after development of ARDS. Comparison with survivors (p < 0.05, Mann–Whitney test).
[More] [Minimize]The effect of the underlying risk factor for ARDS on differences in IL-8 and anti-IL-8:IL-8 complex concentrations was also examined. The major risk factors for ARDS were trauma, sepsis, and other (gastric aspiration, drug overdose, and massive transfusion). The concentrations of IL-8 and anti-IL-8:IL-8 complexes did not differ between these groups (p > 0.05, Kruskal-Wallis ANOVA on ranks) (data not shown).
IL-8 correlated with PMN on Days 1, 3, and 5–7 of the at-risk period, and Days 3, 7, and 14 of ARDS (p < 0.05). The correlations were strong for Days 3 and 5–7 in patients at risk (r2 = 0.60 and 0.50, respectively), and on Days 7 and 14 of ARDS (r2 = 0.50 and 0.40, respectively). Interestingly, no significant association between IL-8 or anti-IL-8:IL-8 complexes and PMN was found on Day 1 or 21 of ARDS. Although there were significant correlations between anti-IL-8:IL-8 complexes and PMN numbers on Day 3 of risk for ARDS and Day 3 of ARDS (p < 0.05), these relationships were weak (r2 = 0.30 and 0.10, respectively). Thus, the relationship between PMN and IL-8 or anti-IL-8:IL-8 complexes was actually strongest in patients at risk, before the onset of ARDS, and not significant at the begining of ARDS, when the lung inflammatory response was the most severe.
The anti-IL-8:IL-8 complex concentrations and LIS values were significantly lower in patients at risk for ARDS (Day 1) than in patients with ARDS on Day 1 (Tables 1 2 3). Therefore, we examined the possibility that LIS would be related to anti-IL-8:IL-8 concentrations. Using polynomial regression analysis, we found that LIS values could be predicted from anti-IL-8:IL-8 complex concentrations (p < 0.05). Lower levels of the complexes in patients at risk related to lower LIS scores, and higher levels in patients with ARDS were associated with higher LIS scores.
LIS values as well as the concentrations of anti-IL-8:IL-8 complexes were significantly elevated in patients with ARDS on Day 1 when compared with patients at risk for ARDS (Day 1) (Tables 1 2 3). In addition, the anti-IL-8:IL-8 complexes/total protein ratios were also higher at the beginning of ARDS than in the at risk group (Figure 3). The association between LIS, anti-IL-8:IL-8 complexes, anti-IL-8:IL-8 complex/total protein ratio, and the development of ARDS was investigated by logistic regression analysis. The LIS was strongly associated with the development of ARDS (p < 0.001), with an odds ratio (OR) of 10.3, and a 95% confidence interval (CI) of 2.9 to 37.1. Anti-IL-8:IL-8 complexes were also associated with development of ARDS (p = 0.03), with an OR of 2.7, and a 95% CI of 1.1 to 6.3. The association between anti-IL-8:IL-8 complexes/total protein ratios and development of ARDS was also strong (p = 0.005), with an OR of 4.1 and a 95% CI of 1.5 to 11.0. These analyses indicate that the probability of developing ARDS increases about 10 times when LIS value increases, about 3 times when the anti-IL-8:IL-8 complex concentration increases, and about 4 times when the anti-IL-8:IL-8 complexes/total protein ratio increases.
The ratios of anti-IL-8:IL-8 complex concentrations to total protein concentrations were significantly higher in patients with ARDS who died (Figure 4). The predictive value of the anti-IL-8:IL-8/protein ratios in relation to outcome of ARDS was assessed by logistic regression analysis. There was a significant association between anti-IL-8:IL-8 complexes and ARDS outcome (p = 0.05), with an OR of 4.5 and a 95% CI of 1.0 to 20.5. The concentrations of anti-IL-8:IL-8 complexes and IL-8 were also marginally higher in nonsurvivors (p = 0.08 and 0.07, respectively) (Figures 1 and 2, Tables 2 and 3). Logistic regression analysis revealed that the association between high anti-IL-8:IL-8 complex concentrations and the probability of dying was strong (p = 0.03), with an OR of 3.0 and a 95% CI of 1.1 to 7.9. However, the presence of high IL-8 concentrations did not affect the probability of dying (p = 0.05, OR = 1.0). In summary, the probability of dying increased by approximately 4.5 times in patients who had high levels of anti-IL-8:IL-8/protein, by about three times in patients with high anti-IL-8:IL-8 complex concentrations, and not at all when IL-8 concentrations alone were considered.
The aim of this study was to determine the relationship between the concentration of anti-IL-8:IL-8 complexes in BAL fluid and the development of ARDS in patients at risk, and the outcome in patients with established ARDS. Our prior studies showed that anti-IL-8:IL-8 complexes are detectable in BAL fluid of patients with ARDS and suggested that anti-IL-8 autoantibodies inhibit the chemotactic activity of IL-8 in vitro (7). This raised the possibility that these antibodies might neutralize IL-8 in vivo and have a protective effect. However, clinical studies have linked anti-IL-8 antibodies with disease activity in asthma and rheumatoid arthritis (13-15). Our results show that there is a significant relationship between the presence of anti-IL-8:IL-8 complexes in the BAL fluids and the course of disease in patients before and after the onset of ARDS. The concentration of anti-IL-8:IL-8 complexes in BAL fluid was significantly higher at the onset of ARDS than in patients at risk for ARDS, and significantly higher at the beginning of ARDS in patients who subsequently died. The patients with ARDS with elevated anti-IL-8:IL-8 complex concentrations were approximately three times more likely to die than were patients with lower concentrations of anti-IL-8:IL-8 complexes in the lungs.
Surprisingly, the IL-8 concentration in the patients at risk did not predict who would progress to ARDS, and the IL-8 concentration on Day 1 of the risk period was almost as high as that measured in BAL fluid at the onset of ARDS. In this series of patients, the IL-8 concentration also did not predict the outcome of ARDS. These findings contrast with prior studies, in which IL-8 concentrations were found to predict the onset and the outcome of ARDS (5, 16-18). Other groups, however, have not found a consistent relationship between IL-8 and survival once ARDS begins (6, 7, 19, 20). Donnelly and coworkers (16) studied patients with trauma, pancreatitis, or perforated bowel as soon as they presented to the emergency department, and found that BAL fluid IL-8 concentrations were elevated without corresponding increases in PMNs. This suggested that IL-8 may be an early marker of the severity of lung injury. Our patients at risk for ARDS were studied within 24 h of the onset of ARDS, often after initial therapeutic measures had been undertaken in the emergency department, the operating room, or the intensive care unit. Substantial numbers of PMNs were present in the BAL fluid of our subjects, along with IL-8, suggesting that we studied at-risk patients as the inflammatory response was developing. This suggests that as intricate inflammatory responses develop in the lungs, IL-8 loses its value as a single predictor of the onset of ARDS. Additional factors that may contribute to discrepancies about the value of IL-8 include differences in patient populations, and the immunoassay used to detect IL-8.
To provide insight about whether the anti-IL-8 autoantibody moves passively into the lungs as protein permeability increases after endothelial and epithelial injury, or whether it might be produced in the lungs, we normalized anti-IL-8:IL-8 complex concentrations for BAL fluid total protein. The ratio of anti-IL-8:IL-8 complexes to total protein was significantly higher at the onset of ARDS than in patients at risk for ARDS. In addition, the patients with ARDS with an elevated anti-IL-8:IL-8/protein ratio were approximately 4.5 times more likely to die than were patients with lower concentrations of anti-IL-8:IL-8 complexes. While this suggested a strong relationship between the complex/protein ratio and both onset and outcome of ARDS, it also suggests that the formation of anti-IL-8:IL-8 complexes is not a simple consequence of increased protein permeability in the lungs. An increase in the complex/protein ratio could be explained by local production of the anti-IL-8 autoantibody within the lungs. Lymphocyte concentrations in BAL fluid do not increase above normal at the onset of ARDS (our unpublished observations), so the production of specific anti-IL-8 antibody would have to occur either from the small number of existing B cells in the alveolar spaces, or from B cells in the interstitium or other lung lymphoid tissue.
Neither free IL-8 nor anti-IL-8:IL-8 complexes were related to the PMN concentration in BAL fluid at the beginning of ARDS. However, on Days 1, 3 and 5–7 of risk, and later in the course of ARDS, significant relationships between IL-8 and PMNs were found. This agrees with prior results in a different series of patients (6), and suggests that the intricate inflammatory response that occurs at the onset of ARDS is driven by a number of different factors. As the inflammatory response evolves, IL-8 becomes a dominant PMN chemoattractant in the lungs. Interestingly, the anti-IL-8:IL-8 complexes were significantly related to PMNs only on Day 3 of risk, and not during the course of ARDS. This is consistent with in vitro observations that IL-8 in anti-IL-8:IL-8 complexes is biologically inactive (7).
The function of autoantibodies to IL-8 is not known. Two previous studies showed that these autoantibodies acted as inhibitors of IL-8 activity in vitro (7, 8). In the present study, we found that the anti-IL-8:IL-8 complexes are related to disease activity, reflected by the onset and outcome of ARDS, but that they are not strongly related to the numbers of PMNs recoverable in BAL fluid. Other clinical studies have also found that anti-IL-8:IL-8 complexes are related to disease activity. For example, Shute and coworkers reported that increased concentrations of IgA:IL-8 in the bronchial mucosa are related to disease activity in patients with asthma (13). The IgA enhanced eosinophil responses to IL-8, including the release of granulocyte-macrophage colony-stimulating factor (GM-CSF) and chemotaxis (14). Elevated concentrations of IgA:IL-8 complexes are also correlated with the clinical severity of rheumatoid arthritis (15).
These observations suggest that there may be other mechanisms by which anti-IL-8:IL-8 complexes contribute to the pathogenesis of inflammation in the lungs. It has been suggested that IL-8 autoantibodies might act as carrier proteins, resulting in a longer half-life in the circulation and in tissue. Finkleman and coworkers reported that a monoclonal anti-interleukin 3 (IL-3) antibody prolonged the half-life of 125I-labeled IL-3 when antibody:IL-3 complexes were injected into rats (21). Similar results were obtained with IL-4 (21), IL-6 (22), and IL-7 (21), suggesting that the formation of antibody:cytokine complexes prolongs the circulation of cytokines. As an additional mechanism, the anti-IL-8:IL-8 complexes may trigger cytokine production by macrophages and other cells in the lungs. Immobilized IgG-containing immune complexes are capable of stimulating IL-8 production directly, or indirectly by augmenting IL-1β release (23, 24). Indeed, immobilized anti-IL-8:IL-8 complexes stimulated human alveolar macrophages to release IL-8 (our unpublished observations). Anti-IL-8:IL-8 complexes may have either cytotoxic or other immunological activity in vivo (25).
In summary, the data show that IL-8 and anti-IL-8:IL-8 complexes accumulate in the lungs as soon as patients are at risk for ARDS, as well as at the onset of ARDS. While IL-8 concentrations are related to PMN recruitment, the anti-IL-8:IL-8 complexes are not strongly related to either PMNs or total protein in the lungs. However, the anti-IL-8:IL-8 complex concentration is related to the course of the disease, as the concentration of anti-IL-8:IL-8 complexes is higher at the onset of ARDS than in patients at risk, and in patients with established ARDS who subsequently die. The biological activity of anti-IL-8:IL-8 complexes in the lungs needs to be determined, and the mechanisms that link anti-IL-8:IL-8 complexes with the course of disease in patients before and after the onset of ARDS merit further study.
Supported by NIH grants HL56768, HL30542, and AI29103 and by the Medical Research Service of the U.S. Department of Veterans' Affairs.
| 1. | Ware LB, Matthay MAThe acute respiratory distress syndrome. N Engl J Med342200013341349 |
| 2. | Weiland JE, Davis WB, Holter JF, Mohammed JR, Dorinsky PM, Gadek JELung neutrophils in the adult respiratory distress syndrome: clinical and pathological significance. Am Rev Respir Dis1331986218225 |
| 3. | Martin TR, Pistorese BP, Hudson LD, Maunder RJFunction of lung and blood neutrophils in patients with the adult respiratory distress syndrome: implications for the pathogenesis of lung infections. Am Rev Respir Dis1441991254262 |
| 4. | Holter JF, Weiland JE, Pacht ER, Gadek JE, Davis WBProtein permeability in the adult respiratory distress syndrome: loss of size selectivity of the alveolar epithelium. J Clin Invest78198615131522 |
| 5. | Miller EJ, Cohen AB, Nagao S, Griffith D, Maunder RJ, Martin TR, Weiner-Kronish JP, Sticherling M, Christophers E, Matthay MAElevated levels of NAP-1/interleukin-8 are present in the airspaces of patients with the adult respiratory distress syndrome and are associated with increased mortality. Am Rev Respir Dis1461992427432 |
| 6. | Goodman RG, Strieter RM, Martin DP, Steinberg KP, Milberg JA, Maunder RJ, Kunkel SL, Walz A, Hudson LD, Martin TRInflammatory cytokines in patients with persistence of the acute respiratory distress syndrome. Am J Respir Crit Care Med1541996602611 |
| 7. | Kurdowska A, Miller EJ, Baughman RP, Matthay MA, Brelsford WG, Cohen ABAnti-interleukin-8 autoantibodies in alveolar fluid from patients with the adult respiratory distress syndrome. J Immunol157199626992706 |
| 8. | Sylvester I, Yoshimura T, Sticherling M, Shröder JM, Ceska M, Peichl P, Leonard EJNeutrophil attractant protein-1–immunoglobulin G immune complexes and free anti-NAP-1 antibody in normal human serum. J Clin Invest901992471481 |
| 9. | Crabtree JE, Peichl P, Wyatt JI, Stachl U, Lindley IJDGastric interleukin-8 and IgA IL-8 autoantibodies in Helicobacter pylori infection. Scand J Immunol3719936570 |
| 10. | Steinberg KP, Milberg JA, Martin TR, Mauder RJ, Cockrill BA, Hudson LDEvolution of bronchoalveolar cell populations in the adult respiratory distress syndrome. Am J Respir Crit Care Med1501994113122 |
| 11. | Matute-Bello G, Liles WC, Radella F, Steinberg KP, Ruzinski JT, Jonas M, Chi EY, Hudson LD, Martin TRNeutrophil apoptosis in the acute respiratory distress syndrome. Am J Respir Crit Care Med156199719691977 |
| 12. | Bernard GR, Artigas A, Brigham KL, Carlet J, Falke K, Hudson L, Lamy M, LeGall JR, Morris A, Spragg RReport on American–European Consensus conference on acute respiratory distress syndrome: definitions, mechanisms, relevant outcomes, and clinical trial coordination. Consensus Committee. J Crit Care919947281 |
| 13. | Shute JK, Vrugt B, Lindley IJD, Holgate ST, Bron A, Aalbers A, Djukanovic RFree and complexed interleukin-8 in blood and bronchial mucosa in asthma. Am J Respir Crit Care Med155199718771883 |
| 14. | Shute JK, Lindley I, Peichl P, Holgate ST, Church MK, Djukanovic RMucosal IgA is an important moderator of eosinophil responses to tissue-derived chemoattractants. Int Arch Allergy Immunol1071995340341 |
| 15. | Peichl P, Pursch E, Bröll H, Lindley IJDAnti-IL-8 autoantibodies and complexes in rheumatoid arthritis: polyclonal activation in chronic synovial tissue inflammation. Rheumatol Int181999141145 |
| 16. | Donnelly SC, Strieter RM, Kunkel SL, Walz A, Robertson CR, Carter DC, Grant IS, Pollok AJ, Haslett CInterleukin-8 and development of adult respiratory distress syndrome in at-risk patient groups. Lancet3411993643647 |
| 17. | Chollet-Martin S, Montravers P, Gibert C, Elbim C, Desmonts JM, Fagon JY, Gougerot-Pocidalo MAHigh levels of interleukin-8 in the blood and alveolar spaces of patients with pneumonia and adult respiratory distress syndrome. Infect Immun61199345534559 |
| 18. | Meduri GU, Kohler G, Headly S, Tolley E, Stentz F, Postlethwaite AInflammatory cytokines in the BAL of patients with ARDS: persistent elevation over time predicts poor outcome. Chest108199513031314 |
| 19. | Jorens PG, Van Damme J, De Backer W, Bossaert L, De Jongh RF, Herman AG, Rampart MInterleukin-8 in the bronchoalveolar lavage fluid from patients with adult respiratory distress syndrome (ARDS) and patients at risk for ARDS. Cytokine41992592597 |
| 20. | Martin TR, Goodman RB. The role of chemokines in the pathophysiology of the acute respiratory distress syndrome (ARDS). In: Hebert CA, editor. Chemokines in disease, 1st ed. Totowa, NJ: Humana Press; 1999. p. 81–110. |
| 21. | Finkelman FD, Madden KB, Morris SC, Holmes JM, Boiani N, Katona IM, Maliszewski CRAnti-cytokine antibodies as carrier proteins: prolongation of in vivo effects of exogenous cytokines by injection of cytokine–anti-cytokine antibody complexes. J Immunol151199312351244 |
| 22. | May LT, Neta R, Moldawer LL, Kenney JS, Patel K, Sehgal PBAntibodies chaperone circulating IL-6. Paradoxical effects of anti-IL-6 “neutralizing” antibodies in vivo. J Immunol151199332253236 |
| 23. | Marsh CB, Gadek JE, Kindt GC, Moore SA, Wewers MDMonocyte Fc gamma receptor cross-linking induces IL-8 production. J Immunol155199531613167 |
| 24. | Marsh CB, Lowe MP, Rovin BH, Parker JM, Liao Z, Knoell DL, Wewers MDLymphocytes produce IL-1beta in response to Fc gamma receptor cross-linking: effects on parenchymal cell IL-8 release. J Immunol160199839423948 |
| 25. | Van der Meide PH, Schellekens HAnti-cytokine autoantibodies: epiphenomenon or critical modulators of cytokine action. Biotherapy1019973948 |
