Carol L. Miller

Changes in Lymphocyte Activity after Thermal Injury: THE ROLE OF SUPPRESSOR CELLS

The high incidence of fatal septicemia associated with severe thermal injury is believed to result from a loss of immunocompetence. To detect burn-mediated immune defects, lymphocyte function in peripheral blood leukocytes from 18 individuals sustaining 20-80% full thickness thermal burns was investigated. We examined the kinetics of the mitogen responses, the development of suppressive activity, and the correlation of mononuclear cell functional abnormalities with the incidence of sepsis. Patients were divided into three groups corresponding to their clinical course. The phytohemagglutinin responses of Ficoll-Hypaque purified leukocytes from eight of these patients (group III) were normal at day 1-2 after injury, but were significantly depressed (mean 16% of normal) at days 5-10 after injury. All of these group III patients experienced multiple, severe, septic episodes, and septic mortality was 75%. The other 10 burned individuals showed either augmented (group II) or unaltered (group I) mitogen responsiveness. Concomitant with evaluation of their mitogen responses, the cells of burn patients were assessed for development of suppressive activity by addition to on-going normal mixed leukocyte reactions (MLR). Only the addition of mononuclear cells with depressed phytohemagglutinin responsiveness (group III) significantly decreased MLR proliferation (mean 80% reduction) by the previously highly responsive, normal MLR combinations. Addition of cells from group III burn patients collected immediately after injury had no suppressive effect. Addition of cells from patients in group I or II or of normal individuals cells had no suppressive effect. These experimental results strongly suggest that a suppressive mononuclear cell is at least partially responsible for the decreased immunocompetence of burn patients.

DMPK dosage alterations result in atrioventricular conduction abnormalities in a mouse myotonic dystrophy model

Myotonic dystrophy (DM) is the most common form of muscular dystrophy and is caused by expansion of a CTG trinucleotide repeat on human chromosome 19. Patients with DM develop atrioventricular conduction disturbances, the principal cardiac manifestation of this disease. The etiology of the pathophysiological changes observed in DM has yet to be resolved. Haploinsufficiency of myotonic dystrophy protein kinase (DMPK), DM locus-associated homeodomain protein (DMAHP) and/or titration of RNA-binding proteins by expanded CUG sequences have been hypothesized to underlie the multi-system defects observed in DM. Using an in vivo murine electrophysiology study, we show that cardiac conduction is exquisitely sensitive to DMPK gene dosage. DMPK-/- mice develop cardiac conduction defects which include first-, second-, and third-degree atrioventricular (A-V) block. Our results demonstrate that the A-V node and the His-Purkinje regions of the conduction system are specifically compromised by DMPK loss. Importantly, DMPK+/- mice develop first-degree heart block, a conduction defect strikingly similar to that observed in DM patients. These results demonstrate that DMPK dosage is a critical element modulating cardiac conduction integrity and conclusively link haploinsufficiency of DMPK with cardiac disease in myotonic dystrophy.

The Immune Consequences of Trauma

This articles provides an overview of current knowledge of trauma-mediated alterations of host defense mechanisms.

Suppressor T-cell activity induced as a result of thermal injury

Abstract Many thermally injured patients survive their initial trauma only to succumb to infection at 2 to 4 weeks after the burn. Both clinical and experimental data have suggested that acute thermal insult compromises immune function. In this report we have sequentially examined the ability of thermally injured mice to generate a specific in vitro primary antibody-forming cell (AFC) response to sheep red blood cells (SRBC) at various times after thermal injury. Thermally injured mice appear to lose the ability to generate de novo antibody-forming cells in vitro after thermal injury. The defect was dissected as to the involvement of macrophage (φ), thymus-derived cell (T-cell), or bursal equivalent (B-cell) defects. Murine B cells from burned animals exhibited normal immunological function in the in vitro AFC system. T cells from burned mice were demonstrated as not only dysfunctional in the generation of immune AFC, but also as able to suppress generation of an AFC response by syngeneic normal cells.

Inhibited neutrophil apoptosis: proteasome dependent NF-kappaB translocation is required for TRAF-1 synthesis.

Neutrophil (PMN) apoptosis regulates local and systemic inflammation during sepsis. Tumor necrosis factor receptor-associated factors (TRAFs) have been implicated as mediators of apoptosis; however, the signaling pathways for their production in stimulated PMN are unclear. We hypothesize that NF-kappaB translocation is necessary for the induction of TRAF-1 in PMNs with prolonged survival. Neutrophils were isolated from the blood of healthy volunteers by Ficoll gradient centrifugation and red blood cell sedimentation. Neutrophil NF-kappaB was inhibited with a proteasome inhibitor, PSI-I. Cells were treated with PSI-I (30 microM) or vehicle (DMSO 0.2%) for 50 min then incubated over an 18-h time course with LPS (10 to 1000 ng/mL), tumor necrosis factor alpha (TNFalpha) (2 to 20 ng/mL) or control media. In vitro apoptosis was quantified by propidium iodide FACS analysis. Total cellular TRAF-1 was detected by Western blot analysis of cell lysates. Steady state TRAF-1 mRNA was detected by RPA. NF-kappaB activity was determined by Western blot analysis for nuclear p65. Means and standard errors were calculated; data were analyzed by ANOVA. Lipopolysaccharide (LPS) and TNFalpha increased PMN nuclear p65 and steady state TRAF-1 mRNA. Apoptosis was inhibited by TNFalpha and LPS at 12 and 18 h (P < 0.01). Incubation of cells in the NF-kappaB inhibitor PSI-I blocked LPS and TNFalpha-induced inhibition of apoptosis (P < 0.05) and the induction of both nuclear p65 and TRAF-1 mRNA. These data demonstrate that inhibition of PMN apoptosis and TRAF-1 induction by LPS and TNFalpha is NF-kappaB dependent.

Thermal injury: Defects in immune response induction☆

Abstract The immunocompetence of leukocyte subpopulations from mice which had received a 10% scald burn has been examined following injury. Leukocytes from the burned animals were reduced 80% in their ability to generate de novo antibody-forming cells in vitro . When leukocytes from the injured animals were supplied with the immunologically active factors produced by normal A and T leukocytes, their immunocompetence was restored. These experiments indicate that: (i) Thermal injury directly reduces the immune activity of leukocytes; (ii) the thermal-induced leukocyte injury is time dependent; and (iii) the leukocyte subpopulation affected is not the antibody-forming B cell.

Inhibition of Neutrophil Apoptosis after Severe Trauma Is NF???? Dependent

Background: Systemic inflammation may inhibit neutrophil (PMN) apoptosis and promote multiple organ dysfunction syndrome. We hypothesize that severe trauma causes dysregulation of PMN apoptosis. Methods: Neutrophils were isolated from trauma patients (24-72 hours after injury; n = 16) and controls (healthy volunteers) and incubated for 18 hours. In separate experiments, control cells were treated ± the nuclear factor kappa beta (NFκβ) inhibitor pyrrolidinithiocarbamate then incubated with 25% patient or control plasma. Apoptosis was quantified by enzyme-linked immunosorbent assay for histone-associated DNA and annexin V fluorescence-activated cell sorter. NFκβ activation was determined by Western blot for phosphorylated Iκβ. Results: Apoptosis was inhibited in trauma patient PMN. Neutrophil apoptosis correlated with multiple organ dysfunction syndrome score, Acute Physiology and Chronic Health Evaluation II, and platelet count. Patient plasma inhibited apoptosis and induced phosphorylation of Iκβ in control cells. Inhibition of PMN apoptosis by patient plasma was blocked by pretreatment with pyrrolidinithiocarbamate. Conclusion: NFκβ-dependent inhibition of neutrophil apoptosis occurs after trauma. Early inhibition of PMN apoptosis is dependent on the magnitude of injury.

Dextran as a modulator of immune and coagulation activities in trauma patients

Low Mr dextran has been utilized as a prophylactic therapy in treatment of coagulopathy. There is evidence that monocyte dysfunctions are important contributors to hypercoagulability episodes, as well as to immunoincompetence post-trauma. Dextran is a known monocyte modulator. Consequently, we evaluated the efficacy of dextran infusion in moderating immune dysfunction, monocyte aberrations, and hypercoagulability episodes. Twenty-eight trauma patients were randomly divided into two groups. One group of 15 received dextran at 1 g/kg wt/24 hr for 5 days in addition to standard resuscitation and treatment. The control or nontreated patient group received only standard treatment. Trauma patients in the two groups were retrospectively matched by injury severity score (ISS) to ensure comparability. Blood samples were collected daily for some studies and at 3-day intervals for other assays. In vivo coagulation status was evaluated by assessing the changes in intravascular fibrinopeptide A (FPA). Immune reactivity to the mitogen phytohemagglutinin (PHA) was also evaluated. Both monocyte production of plasminogen activator (PA) and monocyte production of procoagulant activity (PCA) have been shown to correspond to and be augmented by monocyte-T lymphocyte interactions. Consequently, monocyte production of plasminogen activator and procoagulant activity were assessed as measures of monocyte immune activity as well as indicators of monocyte function in controlling the balance between fibrinolysis and coagulation. Only patients with ISS of greater than 25 experienced significant immune, coagulation, or monocyte aberrations. Of those having an injury severity score (ISS) score of 25-35, all of the control and two of the dextran patients had significant perturbations in their immune and monocyte functions.(ABSTRACT TRUNCATED AT 250 WORDS)

The immunomodulating effect of TP5 and indomethacin in burn-induced hypoimmunity☆

Hypoimmunity after major trauma and thermal injury appears to predispose to septicemia. An increase of immune suppressive T cells and the inhibitory monocytes product PGE2 has been demonstrated postburn and are suggested as contributing to postburn hypoimmunity. TP5, the biologically active part of thymopoientin, has an immunomodulating effect on T cells. Indomethacin, an irreversible blocker of the prostaglandin synthesis has been suggested to reduce the inhibitory monocytes-mediated immunosuppression. In this study strains 2 and 13 guinea pigs received 20-30% TBSA scald burn and were subsequently injected with either TP5 or indomethacin or a combination of both on the 3 following days postburn. The ability of splenocytes to produce a secondary immune response to SRBC was measured in the in vitro AFC assay. The animals who had received TP5 and indomethacin showed significant improvement in their ability to mount an immune response in the AFC assay.