Immune Cellular interactions During Sepsis and Septic injury

Histopathological and cytological examination of autopsy cases with multiple organ dysfunction syndromes

To evaluate the role of small scavenger receptor A (SRA)-positive (SRA(+)) cells and large SRA(+) cells in the peripheral blood (PB) in the pathophysiological mechanisms underlying multiple organ dysfunction syndromes (MODS), 24 autopsy cases with MODS were examined. In addition to histopathological and immunohistochemical examination, cytokine levels of cardiac blood, the SRA index (number of small SRA(+) cells in 10 high power fields, upper limit <30), and appearance of large SRA(+) cells in PB were examined. The SRA index exceeded 30 in all cases. Large SRA(+) cells and tumor necrosis factor (TNF)-alpha(+) cells were detected in PB in all cases. Macrophage colony stimulating factor (M-CSF), interleukin (IL)-6 and IL-8 levels exceeded the normal level in all cases, and 18 and 15 cases had TNF-alpha and IL-1beta levels above the normal threshold, respectively. Lung injury and necrosis of cardiac myocyte were observed in all cases. Neutrophils and platelets accumulated in the capillaries of injured organs and endothelial cells were extensively injured. From these results, large SRA(+) cells differentiated from monocytes in PB were considered to play an important role in the development of MODS, and necrosis of cardiac myocytes together with lung injury might be the leading cause of death in MODS patients.

Differential production of intracellular gamma interferon in alpha beta and gamma delta T-cell subpopulations in response to peritonitis

Flow cytometry was used to measure T-cell intracellular gamma interferon and surface interleukin 2 re-ceptor expression in response to peritonitis in rats. Interleukin 2 receptor expression levels were similar in the two T-cell subsets, but gamma interferon production was increased fivefold in gamma delta T cells compared with pro-duction in alpha beta T cells. Our results provide further evidence of an early and vigorous gamma delta T-cell response to bac-terial infection.

Pathogenic aspects of circulatory shock

Shock has been described and defined by the inciting cause. This method of categorization does little to clarify common pathophysiologic changes known to occur regardless of the etiology. Each type of shock involves different stages that are determined by the inciting cause, its duration, severity of the initial result, susceptibility of the patient, and adequacy of treatment.

Cytokines in plasma and ultrafiltrate during continuous arteriovenous haemofiltration

Cytokines are considered to be important mediators in the pathophysiology of sepsis and septic shock. We investigated if continuous arteriovenous haemofiltration (CAVH) could be used to remove excessive amounts of the cytokines tumour necrosis factor-alpha (TNF alpha), interleukin (IL)-1 alpha and IL-6 from peripheral blood in critically ill patients. Nine septic patients with renal failure were treated with CAVH. Ultrafiltrate and plasma were tested for cytokines by ELISA. All patients had detectable TNF alpha and IL-6 plasma levels, ranging from 10-750 pg/ml and 50-4,575 pg/ml, respectively. TNF alpha was removed by the ultrafiltrate with concentrations ranging from 10-1,000 pg/ml. The TNF alpha levels were significantly higher in the ultrafiltrate samples than in the corresponding plasma samples (P < 0.003). IL-6 was undetectable in the ultrafiltrate from five of the patients despite concomitant high plasma levels. IL-1 alpha was detectable in both plasma and ultrafiltrate in four patients. All patients developed multi-organ failure and septic shock and seven died. It is concluded that TNF alpha and IL-1 alpha but not IL-6 can be removed by CAVH in patients with sepsis.

Acute lung injury: what have we learned from animal models?

In 1950, Carl John Wiggers, philosopher and physiologist, wrote, "Reactions to definite types of stimulation may be observed or recorded, and concealed phenomena may be revealed by the use of apparatus that transforms them into forms that are recognizable by human senses. But complete understanding of physiological reactions often necessitates extensive operative procedures and sometimes the ultimate sacrifice of life. For this reason experimentation on animals is indispensable." Acute lung injury is still a significant cause of death in the developed world, and modern pharmacology and intensive care have failed to alter the clinical course of this complex condition. In the past decade, there was an explosion in understanding of the pathophysiology of acute lung injury, and with this has come the development of a new generation of agents that may provide a tool with which to combat this disorder. Use of animal model systems led to this greater understanding and is currently at the heart of evaluating the new therapeutic agents. This review briefly addresses the contribution animal model systems have made to what appear to be a watershed in attempts to obviate the effects of this mortal condition.

Role of the neutrophil in adult respiratory distress syndrome

Adult respiratory distress syndrome (ARDS) remains a significant cause of morbidity and mortality in surgical practice. Despite the continued advance of surgical technique and therapy, the mainstay of treatment of ARDS remains supportive. In the past decade cytokines have been found to be primary chemical mediators of the host response to inflammatory disease. The polymorphonuclear leucocyte has also emerged as a possible cellular mediator of the end-organ damage that characterizes these inflammatory processes. The role of the neutrophil as the primary cellular mediator of alveolar capillary membrane injury in ARDS remains controversial. This article reviews the relevant current literature and considers the implications of the prevailing evidence on future management of this syndrome.

Perspectives for the future

The pathophysiology of sepsis and septic shock is extremely complex and ultimately involves every physiological pathway. The initiating event is the entrance of endotoxin or similar substances into the blood which initiates the release of multiple mediators. These are designed to react locally and to protect the organism. Their constant release, however, sets in motion up- and down regulations, ultimately resulting in "metabolic anarchy". Tumor necrosis factor alpha and other cytokines trigger several systems, especially coagulation to yield DIC, and the complement system. Many treatment modalities have been developed, most recently those which substitute inhibitors of various systems. Antithrombin III concentrates and potentially protein C concentrates are designed to arrest DIC. C1-esterase inhibitor concentrates should intercept the activation of the complement system and the contact phase of coagulation and its relationship to kinin generation. Even newer approaches entail antibodies to tumor necrosis factor alpha or endotoxin itself. The complex process of sepsis will undoubtedly require a multifaceted therapeutic approach.

The Inflammatory Response

Inflammation is a critical component of the normal healing process. In the patient with extensive injury or infection, however, this same process may lead to organ dysfunction and failure as seen in adult respiratory distress syndrome and multiple organ failure syndrome. In this article we review: (1) the evolution of current concepts of inflammation; (2) individual elements of the host response to inflammatory stimuli; and (3) current strategies for the prevention and treatment of adult respiratory distress syndrome and multiple organ failure syndrome.

From the Department of Surgery, University of Washington School of Medicine, Harborview Medical Center, Seattle, WA.