Temporal Changes in Innate and Adaptive Immunity During Sepsis as Determined by ELISpot.

Background: The inability to evaluate host immunity in a rapid quantitative manner in patients with sepsis has severely hampered development of novel immune therapies. The ELISpot assay is a functional bioassay that measures the number of cytokine-secreting cells and the relative amount of cytokine produced at the single-cell level. A key advantage of ELISpot is its excellent dynamic range enabling a more precise quantifiable assessment of host immunity. Herein, we tested the hypothesis on whether the ELISpot assay can detect dynamic changes in both innate and adaptive immunity as they often occur during sepsis. We also tested whether ELISpot could detect the effect of immune drug therapies to modulate innate and adaptive immunity. Methods: Mice were made septic using sublethal cecal ligation and puncture (CLP). Blood and spleens were harvested serially and ex vivo IFN-γ and TNF-α production were compared by ELISpot and ELISA. The capability of ELISpot to detect changes in innate and adaptive immunity due to in vivo immune therapy with dexamethasone, IL-7, and arginine was also evaluated. Results: ELISpot confirmed a decreased innate and adaptive immunity responsiveness during sepsis progression. More importantly, ELISpot was also able to detect changes in adaptive and innate immunity in response to immune-modulatory reagents, for example dexamethasone, arginine, and IL-7 in a readily quantifiable manner, as predicted by the reagents known mechanisms of action. ELISpot and ELISA results tended to parallel one another although some differences were noted. Conclusion: ELISpot offers a unique capability to assess the functional status of both adaptive and innate immunity over time. The results presented herein demonstrate that ELISpot can also be used to detect and follow the in vivo effects of drugs to ameliorate sepsis-induced immune dysfunction. This capability would be a major advance in guiding new immune therapies in sepsis.

Differential effects of physiologically relevant hypoxic conditions on T lymphocyte development and effector functions.

Direct measurements revealed low oxygen tensions (0.5-4.5% oxygen) in murine lymphoid organs in vivo. To test whether adaptation to changes in oxygen tension may have an effect on lymphocyte functions, T cell differentiation and functions at varying oxygen tensions were studied. These studies show: 1) differentiated CTL deliver Fas ligand- and perforin-dependent lethal hit equally well at all redox conditions; 2) CTL development is delayed at 2.5% oxygen as compared with 20% oxygen. Remarkably, development of CTL at 2.5% oxygen is more sustained and the CTL much more lytic; and 3) hypoxic exposure and TCR-mediated activation are additive in enhancing levels of hypoxia response element-containing gene products in lymphocyte supernatants. In contrast, hypoxia inhibited the accumulation of nonhypoxia response element-containing gene products (e.g., IL-2 and IFN-gamma) in the same cultures. This suggests that T cell activation in hypoxic conditions in vivo may lead to different patterns of lymphokine secretion and accumulation of cytokines (e.g., vascular endothelial growth factor) affecting endothelial cells and vascular permeabilization. Thus, although higher numbers of cells survive and are activated during 20% oxygen incubation in vitro, the CTL which develop at 2.5% oxygen are more lytic with higher levels of activation markers. It is concluded that the ambient 20% oxygen tension (plus 2-ME) is remarkably well suited for immunologic specificity and cytotoxicity studies, but oxygen dependence should be taken into account during the design and interpretation of results of in vitro T cell development assays and gene expression studies in vivo.

Regulation of chicken gizzard ecto-ATPase activity by modulators that affect its oligomerization status.

The major ectonucleoside triphosphate phosphohydrolase in the chicken gizzard smooth muscle membranes is an ecto-ATPase, an integral membrane glycoprotein belonging to the E-ATPase (or E-NTPDase) family. The gizzard ecto-ATPase is distinguished by its unusual kinetic properties, temperature dependence, and response to a variety of modulators. Compounds that promote oligomerization of the enzyme protein, i.e., concanavalin A, chemical cross-linking agent, and eosin iodoacetamide, increase its activity. Compounds that inhibit some ion-motive ATPases, e.g., sulfhydryl reagents, xanthene derivatives, NBD-halides, and suramin, also inhibit the gizzard ecto-ATPase, but not another E-ATPase, the chicken liver ecto-ATP-diphosphohydrolase, which contains the same conserved regions as the ecto-ATPase. Furthermore, inhibition of the gizzard ecto-ATPase by these compounds as well as detergents is not prevented by preincubation of the membranes with the substrate, ATP, indicating that their interaction with the enzyme occurs at a locus other than the catalytic site. On the other hand, the inhibitory effect of these compounds, except suramin, is abolished or reduced if the membranes are preincubated with concanavalin A. It is concluded that these structurally unrelated modulators exert their effect by interfering with the oligomerization of the ecto-ATPase protein. Our findings suggest that, under physiological conditions, the gizzard smooth muscle ecto-ATPase may exhibit a range of activities determined by membrane events that affect the status of oligomerization of the enzyme.

Perforin is required for primary immunity to Histoplasma capsulatum.

Protective immunity against primary and secondary infection by the fungus Histoplasma capsulatum (HC) is multifactorial, requiring cells of the innate and adaptive immune response. Effector mechanisms that could mediate intracellular killing of HC include cytokines such as IFN-gamma and TNF-alpha and/or direct cytolytic activity by T and NK cells. In this regard, although previous work has clearly demonstrated a critical role for IFN-gamma and TNF-alpha in limiting fungal growth in primary HC infection, less is known regarding the role of cytolytic mechanisms. The studies reported here first address the role of perforin in mediating immunity to HC. Remarkably, perforin-deficient knockout (PfKO) mice were shown to have accelerated mortality and increased fungal burden following a lethal or sublethal primary challenge. These data established an essential role for perforin in primary immunity systemic HC infection. Interestingly, depletion of CD8(+) T cells in PfKO mice caused a further increase in fungal burden and accelerated mortality, suggesting a perforin-independent role for CD8(+) T cells. Moreover, adoptive transfer of CD8(+) T cells from PfKO mice into IFN-gamma(-/-) mice caused a reduction in fungal burden following infectious challenge compared with control IFN-gamma(-/-) mice. Together, these data suggest that CD8(+) T cells can mediate immunity to HC through both perforin-dependent and -independent mechanisms.

Ecto-protein kinases: ecto-domain phosphorylation as a novel target for pharmacological manipulation?

An increasing number of studies document the presence of protein kinases facing outwards at the cell surface of a diverse array of cells. These ecto-protein kinases phosphorylate cell-surface proteins and soluble extracellular substrates, and thus could affect many physiological processes involving cell-cell contacts, cellular differentiation and proliferation, ion fluxes and cellular activation. To date, only limited attention has been paid to exploring ecto-protein kinases as possible pharmacological targets. Here, the identification and physiological role of ecto-protein kinases in different biological systems is described; it is suggested that ecto-protein kinases are attractive and novel candidates for pharmacological manipulation under various (patho)physiological conditions.

Ectonucleotidases of avian gizzard smooth muscle and liver plasma membranes: a comparative study.

Extracellular nucleotides, e.g., ATP, ADP, and UTP, are important signaling molecules which elicit various physiological responses in different tissues. Their degradation is catalyzed by ectonucleotidases which are located on cell surfaces. Most tissues have a mixed population of ectonucleotidases. In this report, the ATP and ADP hydrolyzing ectonucleotidases of chicken gizzard smooth muscle and liver plasma membranes were studied. The two membranes exhibited marked differences in the ratio of ATPase/ADPase activities, activation by divalent cations, thermal stability, responses to detergents and cross-linking agents, and sensitivity to several enzyme inhibitors. The ATPase activity of chicken gizzard membranes is (i) labile to heat and detergents; (ii) activated by concanavalin A and disuccinimidyl suberate, both cross-linking agents; (iii) inhibited by mercurials; and (iv) insensitive to high concentrations of azide, a known inhibitor of ecto-ATP diphosphohydrolases (ecto-ATP/Dase). In contrast, the liver membrane ATPase and ADPase activities are more stable to treatment by heat and detergents and insensitive to cross-linking agents and mercurials, but are inhibited by azide. A low ADP hydrolase activity in the gizzard membranes could be distinguished from both the gizzard ATPase and the liver ATPase/ADPase. This ADP hydrolase, which is markedly stimulated by NBD-Cl, accounts for most of the ADP hydrolysis activity in gizzard membranes. It is concluded that the major ectonucleotidase in the gizzard membranes is an ecto-ATPase whereas that in the liver membranes is an ecto-ATP/Dase. That both membranes contain a mixed population of the ecto-ATPase and ecto-ATP/Dase, but in different proportions, is further demonstrated by immunochemical characterization. The different composition of ectonucleotidases in the two membranes is expected to have an important effect on the regulation of hydrolysis of extracellular ATP as well as the concentration of extracellular adenine nucleotides in the gizzard and liver tissues.

Nicotine patch therapy for smoking cessation combined with physician advice and nurse follow-up. One-year outcome and percentage of nicotine replacement.

OBJECTIVE: To determine the efficacy of a 22-mg nicotine patch combined with the National Cancer Institute program for physician advice and nurse follow-up in providing withdrawal symptom relief, 1-year smoking cessation outcome, and percentage of nicotine replacement. DESIGN: Randomized, double-blind, placebo-controlled trial. SUBJECTS: Two-hundred forty healthy volunteers who were smoking at least 20 cigarettes per day. INTERVENTIONS: Based on the National Cancer Institute program, subjects received smoking cessation advice from a physician. Follow-up and relapse prevention were provided by a study nurse during individual counseling sessions. Subjects were randomly assigned to 8 weeks of a 22-mg nicotine or placebo patch. MAIN OUTCOME MEASURES: Abstinence from smoking was verified by expired air carbon monoxide levels. Withdrawal symptoms were recorded during patch therapy, and the percentage of nicotine replacement was calculated by dividing serum nicotine and cotinine levels at week 8 of patch therapy by levels obtained while smoking. RESULTS: Higher smoking cessation rates were observed in the active nicotine patch group at 8 weeks (46.7% vs 20%) (P < .001) and at 1 year (27.5% vs 14.2%) (P = .011). Higher smoking cessation rates were also observed in subjects assigned to the active patch who had lower serum levels of nicotine and cotinine at baseline, and withdrawal symptom relief was better in the active patch group compared with placebo. CONCLUSIONS: Clinically significant smoking cessation can be achieved using nicotine patch therapy combined with physician intervention, nurse counseling, follow-up, and relapse prevention. Smokers with lower baseline nicotine and cotinine levels had better cessation rates, which provides indirect evidence that they had more adequate nicotine replacement with this fixed dose of transdermal nicotine than those smokers with higher baseline levels.

Dynamic trend monitoring of cerebral blood flow velocity in newborn infants.

A method for obtaining reproducible Doppler cerebral blood flow velocity (CBFV) measurements over several hours, utilizing a probe fixation technique and an on-line system for making beat-to-beat area under the curve (AUC) measurements, is described. Thirty heartbeat samples were collected at three time intervals over 3 hours in a group of 22 healthy preterm infants. The stability of the AUC measurements despite changes in behavioral state was demonstrated by randomized block ANOVA. The sampling error was +/- 6.92%, with 95% confidence intervals of +/- 13.1%. By facilitating reproducible serial measurements of CBFV, this trend monitoring technique encourages a dynamic view of cerebrovascular control, and may be used to probe central nervous system autoregulatory pathophysiology and to evaluate the effects of therapeutic interventions.

Intubation-related tracheal stenosis in very-low-birth-weight infants. Diagnosis and treatment.

Five infants who developed intubation-related tracheal stenosis were treated surgically with an anterior cricoid split instead of a tracheostomy. This surgery allowed early extubation and discharge of these patients who, on follow-up, have had adequate phonation and no further respiratory compromise. We suggest that this surgery be considered for all infants who develop intubation-related tracheal stenosis.

Osteomyelitis of the great toe secondary to phlebotomy.

A premature infant developed Staphylococcus osteomyelitis secondary to multiple punctures of the great toe for drawing blood. The infection responded well to antibiotic therapy.

A widespread epidemic of mild necrotizing enterocolitis of unknown cause.

Within a 28-day period, necrotizing enterocolitis (NEC) developed in 20 of 38 infants (53%). Patients with NEC were compared with the remaining 18 infants hospitalized at the same time who did not acquire the disease. Complications of pregnancy and labor-delivery and infant care practices did not differ between groups. Mean chronologic age was significantly different between patients with NEC and those without, 29 days v 77 days. Mean postconceptional age at the time of the outbreak was also significantly different, 33.4 weeks v 42.3 weeks. None of the cultures demonstrated a specific common pathogen. The low mortality (5%) and the large number of infants affected suggest an atypical out-break of NEC. We could not isolate a causative agent despite extensive epidemiologic investigation, and suggest that postconceptional age delineates those at risk.

Effects of assisted ventilation on echocardiographic findings in two infants with patent ductus arteriosus.

Echocardiography is a useful means of determining whether or not to ligate the patent ductus arteriosus (PDA) in premature infants with respiratory distress syndrome and PDA. The magnitude of the left-to-right ductal shunt can be gauged by measuring the diameter of the left atrium (LA) and aortic root (AO) echocardiographically and by determining the LA/AO ratio. An increase in this ratio during weaning from assisted ventilation is an indication for ligation of the PDA. We recently used this criterion in treating 2 infants with respiratory distress syndrome and PDA.