Search

The agent(s) and mechanism(s) responsible for suppression of neutrophil chemotaxis in association with major thermal injury have not been identified. We have proposed that the reduced random motility characterizing patients' cells may contribute to their generalized chemotactic dysfunction. Here we report that actin polymerization may be responsible for the loss of neutrophil motility associated with major thermal injury. Using a fluorescent ligand specific for polymerized or filamentous actin (NBD-phallacidin) in conjunction with flow cytometry, we have discovered that peripheral blood and exudate neutrophils from patients with major thermal injury contain increased levels of actin in a stably polymerized form. Because cyclic polymerization and depolymerization of actin is essential to cell motility, we suggest that actin polymerization may contribute in a major way to the attenuation of neutrophil random and chemotactic functions induced by major thermal injury.

At laparotomy, many surgeons routinely instill crystalloid solutions into the peritoneal cavity, presumably to dilute out necrotic debris, bacteria, and adjuvant substances which foster bacterial growth. We examined the effect on mortality, bacterial growth, clearance, and phagocytosis of various volumes of saline instilled into the peritoneal cavity of rats during Escherichia coli peritonitis. Minimal intraperitoneal bacterial growth was seen after the introduction of a nonlethal inoculum of viable E. coli in 1 ml of saline, while administration of an identical inoculum in 30 ml of saline intraperitoneally (i.p.) led to increased 48-hour mortality (p less than 0.01), and associated rapid bacterial proliferation (p less than 0.01). Clearance of nonviable radiolabelled E. coli from the peritoneal cavity was delayed, bacterial association with host peritoneal leukocytes was decreased, and blood uptake of radiolabelled bacteria was diminished in animals receiving 30 ml of saline i.p., compared to controls which received the identical inoculum in 1 ml of saline i.p. The clinical relevance of these studies is manifold: (1) they provide a possible explanation why patients with ascites due to cirrhosis or the nephrotic syndrome, or those patients undergoing peritoneal dialysis are more susceptible to primary and secondary bacterial peritonitis, possibly on the basis of impaired peritoneal clearance or diminished phagocytosis and, (2) although irrigation of the peritoneal cavity with crystalloid solution would seem prudent during laparotomy, these solutions must be removed prior to closure to prevent interference with normal peritoneal host defense mechanisms.

Thermal injury is well known to inhibit functions of the circulating neutrophil related to its role in host defense against infection, but the mechanism(s) of this phenomenon are not fully understood. To gain further clues to these mechanisms, the authors have studied patients with thermal injury in terms of altered expression of neutrophil cell membrane receptors for the opsonic complement-derived ligand C3bi--complement receptor Type 3, or CR3. CR3 expression was selected for study because an increase in the number of receptors on the cell surface can be stimulated by products of complement activation known to accumulate after thermal injury and because of the role of CR3 in phagocytic and adherence functions of the neutrophil. Expression of CR3 was monitored semiquantitatively by flow cytometry with the use of a murine monoclonal antibody (OKM1) specific for an antigen (CD11) associated with this receptor. Patients evaluated were limited in this study to those with minor degrees of thermal injury (second-degree burn involving less than 20% of total body surface area) so that possible confounding effects of major injury and its complications could be eliminated. It was observed that patient neutrophil CR3 becomes significantly up-regulated during the first week, as early as 1 day after injury. The maximum level of expression of CR3 averaged greater than 150% (range, 70-314%) of the respective minimum level observed for each patient. The minimum levels of expression of CR3 on patient neutrophils, reached 11-37 days after injury for 7 of 8 patients, were comparable to the level of expression of CR3 on unstimulated control neutrophils. Such temporal up-regulation of patient neutrophil CR3 suggests the early generation of stimuli of CR3 mobilization in response to thermal injury. Increased numbers of CR3 on patient neutrophils may augment microbicidal function and enhance or inhibit delivery of cells to the burn site.