Verlyn M. Peterson

Early neutrophil sequestration after injury: a pathogenic mechanism for multiple organ failure.

Polymorphonuclear neutrophils (PMNs) play a pivotal role in the inflammation that precedes multiple organ failure (MOF). In a rat model of MOF, PMNs become primed for enhanced superoxide anion (O2-) release and CD11b expression, sequester in end organs, and produce organ failure. Therefore, we hypothesized that circulating PMNs harvested in the first 24 hours after injury from trauma patients at risk for MOF would (1) exhibit a primed O2- release, (2) upregulate CD11b expression, and (3) show evidence of sequestration in tissues. Extracellular PMN O2- release and CD11b receptor expression were measured at 3, 6, 12, and 24 hours after injury in 33 torso trauma patients with Injury Severity Scores > 15; eight patients (24%) developed MOF. Healthy adults served as controls. PMNs after injury were primed for enhanced in vitro O2- release at 3, 6, 12, and 24 hours after injury, indicating prior in vivo priming. CD11b expression was also increased at 6, 12, and 24 hours after injury. Circulating PMN numbers increased sharply at 3 hours after injury, before decreasing dramatically at 6 and 12 hours, suggesting end organ sequestration. At 12 hours after injury, declines in circulating PMNs were significantly greater in MOF than in non-MOF patients (p < 0.05). These data indicate that PMNs are quickly mobilized into the circulation after injury and then primed for enhanced O2- release and CD11b expression. PMN priming appears to be a necessary preamble to PMN sequestration in patients with major torso trauma. Upregulation of PMN function, accompanied by subsequent end organ sequestration, may represent an important early event in the pathogenesis of MOF after injury.

Base deficit after major trauma directly relates to neutrophil CD11b expression: a proposed mechanism of shock-induced organ injury

Objective: To determine whether expression of neutrophil integrin receptors is related to the degree of post-traumatic shock. Design: Data were collected prospectively on patients with major trauma admitted to the surgical intensive care unit. Setting: Denver General Hospital, Colorado. Patients and participants: 17 severely injured adults. Measurements and results: The mean fluorescence intensity and per cent positive of neutrophil integrin receptors CD11 b, CD18 and CD11 a, and systolic blood pressure, blood transfusion, lactate and base deficit as indices of shock. CD11 b expression on circulating neutrophils was increased 6 and 12 h after trauma. After correcting for the other shock indices, base deficit predicted CD11 b expression at 12 h. CD11 b expression was negatively correlated with the circulating neutrophil count. Conclusions: The degree of metabolic acidosis after trauma correlates directly with CD11 b receptor expression on circulating neutrophils. This relation may be the mechanism whereby post-traumatic shock results in neutrophil sequestration and neutrophil-mediated organ injury and failure.

Characterization of the immunosuppressive effect of burned tissue in an animal model

The immunosuppressive effect of burned tissue was studied using a mouse burn model. To evaluate the immunologic status an in vivo measure of cell-mediated immunity (CMI) involving contact sensitization of mice by painting the skin with dinitrofluorobenzene was used; mice were challenged 5 days later by painting the ear with the same antigen. Ear swelling in response to antigenic challenge was used as a quantitative measure of CMI; diminution in ear swelling in treatment mice compared to sensitized, unburned control mice indicated the degree of immunosuppression. A full-thickness steam burn covering 20% body surface ares (BSA) was profoundly immunosuppressive as reflected by ear swelling of 45 to 60% of that found in normal mice; partial thickness burns and burns of 10% BSA extent were not significantly immunosuppressive. Transfer into unburned mice of burned skin equivalent in size to a 20% BSA burn eschar resulted in marked immunosuppression, but transfer of smaller amounts of burned skin, or of larger amounts of unburned skin and normal and burned liver tissue, did not produce immunosuppression. Mice receiving a very high-temperature (300 degrees C), dry burn were only slightly more suppressed than mice receiving a standard steam burn. Normal immunity was preserved in burned mice which received daily application of cerium nitrate to the wound for 7 days, but application of other topical agents commonly used in burn treatment did not preserve immunity. Postburn immunosuppression thus appears related quantitatively to toxic factors in burned skin, and these toxic factors can be abrogated in burned mice by the topical application of cerium nitrate.

Immunomodulation Following Burn Injury

Severe burn injury is accompanied by suppression of almost all the components of immunity; such suppression undoubedly contributes to infectious complications in the burned patient. There has now been substantial experimental progress made in devising approaches to prevent or minimize these immune defects; however, clinical application is still limited.

Granulocyte Stem Cells Are Decreased in Humans with Fatal Burns

The number of granulocytic stem cells (CFU-C) was measured in the peripheral blood of surviving and nonsurviving burned humans. It has been shown that the number of CFU-C in the peripheral blood of survivors increases over time and is elevated compared to the number found in normal humans. The number found in nonsurvivors, however, falls significantly in the later stages of burn injury, suggesting perhaps a defect in stem cell production and/or differentiation in patients with severe thermal injuries. The mechanism is unclear but its delineation may have an important bearing on understanding the nature of infectious complications following thermal injury.

The haematopoietic response to burning: studies in an animal model.

Changes in haematopoiesis which occur in humans after burning injury may have important effects on morbidity and mortality. Because of the heterogeneity of burn patients we studied the regulation of blood cell formation which occurs in an animal using an established mouse model. Mice received a 20 per cent third degree scald injury on the back. Serial studies of a variety of haematopoietic parameters including stem cell, bone marrow and peripheral blood findings were done post burn. Although anaemia occurred frequently after injury red blood cell survival studies and examination of the stool for occult blood showed that neither haemolysis nor blood loss were primary causes of the anaemia. Bone marrow erythroid stem cells fell markedly post burn and this was associated with the development of a substance in serum capable of inhibiting red cell colony formation but not white cell colony formation of normal marrow cells. Reticulocytosis occurred but was mild and the anaemia was primarily of the aregenerative type. Partial compensation for the depressed marrow erythropoiesis occurred in the spleen with an increase in erythroid colony-forming cells and erythroblasts. Marked granulocytosis occurred in the peripheral blood and bone marrow. There was an increase in splenic granulocytic stem cells post burn. Megakaryocytosis was striking in the bone marrow and spleen and there was an increase in peripheral blood platelet count. Evidence of immune stimulation included an increase in the size of the spleen and an increase in peripheral blood and splenic lymphocytes. Correlations of many of these findings suggested that the events were not occurring at random but that the changes in haematopoiesis were linked together. We speculate that the anaemia was the result of the increase in granulopoietic and thrombopoietic effort seen post burn.

The anemia of thermal injury: studies of erythropoiesis in vitro.

Anemia is invariably seen in patients who have been severely burned, and a number of factors have been implicated in its etiology. Prior studies have suggested that a depressed rate of erythropoiesis is involved. In order to study this, we evaluated the effect of serum from burned patients on red cell and white cell colony growth in vitro. We found that these sera were capable of inhibiting red cell, but not white cell, colony growth. Additional experiments indicated that this was related to the presence of some substance in the burned serum rather than the absence of a factor required for colony formation. Further studies, including review of clinical data, suggested that this effect was not due to topical medications nor to episodes of bacterial sepsis. Serial studies showed that inhibition was often not present in the immediate postburn period but developed gradually, reaching maximum intensity approximately 20 to 30 days following the burn and then returning toward normal as patients healed their injury. Our studies permit the hypothesis that inhibition of erythropoiesis plays a role in the pathogenesis of the anemia of thermal injury.

Vitamin E improves cell-mediated immunity in the burned mouse: A preliminary study

Profound immunosuppression occurs after major burn injuries. The ability of vitamin E to prevent post-burn immunosuppression was tested in mice using ear swelling in response to a challenge with 2,4-dinitrofluorobenzene (DNFB) as an in vivo measure of cell-mediated immunity (CMI). Vitamin E was administered to burned mice every other day for 14 days by either the topical or intraperitoneal route. Dimethyl sulphoxide (DMSO) was compared to white petroleum jelly (VAS) as a vehicle for topically administered vitamin E. Mean CMI +/- the standard error of the mean (SEM) was depressed to 55 +/- 4 per cent of normal control in untreated burned mice. Treatment with either parenteral vitamin E in corn oil or topical vitamin E in DMSO improved CMI dramatically compared to burned controls (P less than 0.005) while vitamin E in VAS had a less beneficial effect on CMI (P less than 0.05). We conclude that vitamin E is an effective immunomodulator in burned mice.