John L. Ninnemann

Immunologic Defenses Against Infection: Alterations Following Thermal Injuries

It is generally recognized that infection is one of the most important barriers to the successful treatment of major thermal injuries. Indeed, clinical effectiveness is sometimes limited by our lack of understanding of the complex immunologic interactions that predispose burn patients to life-threat

Prostaglandins and immunity

The prostaglandins are a family of biologically active compounds generated from unsaturated fatty acids. They are produced and found in every tissue of the body and their diverse biological activities and possible role in human disease processes are receiving much attention. There is increasing evidence that these compounds are a vital component of the balance achieved by normal immunoregulatory mechanisms. How this balance is achieved, the cells involved, and the consequence of an imbalance in prostaglandin production or consumption are the subject of the articles which follow.

Endotoxemia after burn injury: effect of early excision on circulating endotoxin levels.

Serial circulating endotoxin measurements (quantitative chromogenic limulus assay) were performed in sera from 19 burned patients to determine the profile of circulating serial circulating endotoxin after burn and the effect of early wound excision on serial circulating endotoxin level. Results indicate an early endotoxemia with the peak serial circulating endotoxin levels 7 to 12 hours and 4 days after burn. More importantly, the level of circulating serial circulating endotoxin can be diminished by early excision; late wound excision was associated with a transient increase of serial circulating endotoxin level. Early excision, therefore, may play a critical role in limiting endotoxemia after burn injury.

Suppression ofin vitro lymphocyte and neutrophil responses by a low molecular weight suppressor active peptide from burn-patient sera

Thermal injury produces profound pathophysiological changes in the severely burned patient. Primary among these is the modulation of immunity, leading to episodes of immunosuppression and thus increasing the risk of sepsis and possible death. We herein report the isolation of a low molecular weight suppressor active peptide (SAP) which appears to be responsible for many of the observed immunologic changes in burned patients. SAP suppressed T-lymphocyte blastogenesis in the mixed lymphocyte reaction (MLR) and inhibited neutrophil chemotaxis (CTX)in vitro. Characterization of SAP revealed a complex structure comprised of (1) a peptide component rich in glycine, serine, and alanine; (2) a carbohydrate component containing sialic acid; and (3) a fatty acid component, tentatively identified as prostaglandin E. The immunosuppressive activity of SAP is dependent upon the presence of all three structural components. The molecular weight of SAP was estimated to be 3654 as determined by Amicon cell ultrafiltration and amino acid analysis. The isoelectric point of SAP was estimated by chromatofocusing and ion-exchange chromatography to be between 3.2 and 3.6. We hypothesize that the suppressor active peptide may be comprised of cellular or tissue components released into the circulation at the time of injury.

Trauma peptide induction of lymphocyte changes predictive of sepsis

Post-trauma immunosuppression is characterized by T-cell subpopulation changes and the presence of a low molecular weight suppressive active peptide (SAP), which suppresses T-cell blastogenesis and neutrophil chemotaxis. This study evaluated post-trauma T-cell antigens and suppressive active peptide/T-cell interactions to determine if the suppressive active peptide concentrations predictive of sepsis can cause changes in antigen expression predictive of sepsis. Human lymphocyte markers and differentiation antigens were analyzed post-trauma using flow cytometry for markers predictive of sepsis. Changes induced by purified suppressive active peptide incubated with normal human lymphocytes were similarly analyzed by flow cytometry. SAP concentrations for incubation were chosen which correlated with concentrations in patients developing clinical sepsis. Significant T-cell changes in patients who developed sepsis include: decreased total T-cells, decreased helper cells, decreased natural killer cells, increased Ia expressing mononuclear cells, increased activated T-cells, (L22) and increased IL-2 expressing cells (TAC). Suppressive active peptide can activate T-cells and cause significant increased expression of IL-2 receptors and natural killer cells. Other T-cell changes following trauma predictive of sepsis seem to occur independent of in vitro incubation with suppressive active peptides. IL-2 expressing cells are known to be more readily suppressed by the suppressive peptide. Suppressive peptide activation and subsequent inhibition of T-cells suggests a potential way to explain suppressive peptide-induced immunosuppression following trauma.

Trauma, Sepsis, and the Immune Response

Burn patients, multiple trauma patients, and patients undergoing major surgical operations often suffer from acquired immunologic deficits that predispose them to life-threatening sepsis. This paper reviews the current research in this area, with emphasis on identifying the components of the immune response affected by injury, elucidating the mediators of immunologic change, and determining new therapeutic approaches for correcting immunologic deficits. Lessons learned from the study of immune deficiency disease are reviewed, as are basic observations of burn- and trauma-induced immune depression.

Trauma peptide-mediated prostaglandin E2 biosynthesis: a potential mechanism for trauma-induced immunosuppression

In vitro exposure of peripheral-blood-adherent mononuclear cells or amnion cells to nanomolar quantities of a trauma-associated immunosuppressive peptide resulted in an increased biosynthesis of prostaglandin E2 (PGE2). Trauma peptide enhanced prostaglandin E2 biosynthesis by as much as 425% compared to buffer controls. The addition of trauma peptide to mixed lymphocyte cultures significantly inhibited [3H]thymidine incorporation by human peripheral blood lymphocytes. Addition of indomethacin (an inhibitor of prostaglandin biosynthesis) to mixed lymphocyte cultures did not significantly abrogate the immunosuppressive activity of the peptide. These results indicate that suppression of T lymphocyte blastogenesis by trauma peptide is probably mediated by at least two mechanisms: (1) by increased PGE2 biosynthesis, induced by trauma peptide, and (2) through a non-cyclooxygenase-mediated pathway.

Generation and Activity of Suppressor Peptides Following Traumatic Injury

Severe trauma is known to produce pathophysiologic changes leading to the generation of immunosuppressive compounds. With recent advances in biotechnology, a number of these factors have been identified and characterized. Many of these substances have been found to be degradation products of normal serum and tissue proteins. These degradation products have profound biologic activity both in vivo and in vitro. This report briefly focuses on a number of these factors and summarizes the current work involved in the determination of the identity and mechanisms of a previously reported suppressor-active peptide isolated from the serum of trauma patients.

Toxic epidermal necrolysis complicated by severe wound sepsis: a case study.

The case of a 74-year-old female who developed toxic epidermal necrolysis (30% TBSA) is presented. Despite early, aggressive treatment, the patient developed severe wound sepsis and multiple-system organ failure. The fulminant wound sepsis was preceded by early endotoxemia. Patient serum suppressed T lymphocyte blastogenesis in the mixed lymphocyte reaction test and neutrophil chemotaxis in vitro. Endotoxin removal (affinity chromatography) resulted in a reverse of serum suppressive activity against T lymphocytes but did not reverse inhibition of PMN chemotaxis. Circulating endotoxin levels remained detectable during the entire course while blood cultures remained negative. It is our belief that early endotoxemia (detected before clinical signs of wound sepsis becomes apparent) leads to immunosuppression and other systemic complications.

Deletion of immunoregulatory cells during ficoll-sodium metrizoate isolation of human peripheral blood lymphocytes

Abstract The separation of cells using 1.077 g/ml density Ficoll-sodium metrizoate may not be appropriate for the study of lymphocyte mitogen responses, or probably other tests as well, as it appears to selectively delete an immunoregulatory lymphocyte subpopulation. We have evaluated two common methods of separating lymphocytes for study from peripheral whole blood, Ficoll-sodium metrizoate centrifugation and simple sedimentation/cotton column purification, which yield cell populations quite similar in viability and in proportion of E-rosetting cells. Yet cultures of lymphocytes isolated by the two methods differ considerably in their response to PHA stimulation and in the suppressibility of this response by the addition of serum from cancer patients. By sequentially separating peripheral blood first by sedimentation/cotton column purification, then again by Ficoll-sodium metrizoate centrifugation, two distinct populations of cells were obtained, neither of which could respond well to PHA stimulation alone, nor exhibit suppression by cancer serum supplementation. However, when the two lymphocyte populations were mixed in proportions similar to those found in whole blood, PHA stimulatory and suppressor activities were restored. The lymphocyte subpopulation with density greater than the 1.077 g/ml Ficoll-sodium metrizoate was found to regulate in vitro lymphocyte response to PHA.