Simultaneous determination of the heat and the quantity of vapor sorption using a novel microcalorimetric method

PURPOSE

In this study, instrumentation for measuring vapor sorption enthalpies and sorption uptakes simultaneously with an isothermal microcalorimeter is introduced. Various pharmaceutical model substances undergoing phase transitions when exposed to humid conditions (25 degrees C), were employed to evaluate the usefulness and sensitivity of the constructed experimental method.

METHODS

The sample is placed in the sample vessel of a RH cell and the moisture content of the air flow is controlled. From the RH cell the air flow is conducted into a subsequent perfusion cell in which a saturated salt solution has been loaded. The RH cell and perfusion cells are positioned in the sample sides of two twin calorimetric units. Depending on the moisture content in the outlet flow leaving the preceding RH cell, the heat flow signal from the subsequent perfusion cell will vary. By means of blank measurement with identical settings, the rate of water sorption can be calculated and, by integration, the amount of sorbed water is obtained.

RESULTS

Amorphous lactose and cefadroxil undergo recrystallization when the moisture level in the surroundings exceeds the threshold values specific to each compound. During the sorption phase, heat is evolved fairly linearly as a function of consumed moisture, and also after the recrystallization, the heats indicate linear behavior. The heat values for the desorption phase of amorphous lactose and the adsorption of crystalline lactose coincide. With the different anhydrous forms of theophylline, the hydration takes place more rapidly in the metastable form 1, and generally, the process is more energetic in form 1. In all cases, the gravimetric results agree with the water sorption uptakes calculated from the calorimetric data.

CONCLUSIONS

The technique introduced offers a rapid and sensitive method to gain new insights into the transitions in which vapors are involved. In addition, different kinds of surfaces with various energetics can now be studied more closely.

Genotypic, phenotypic and functional analysis of CD4+CD7+ and CD4+CD7- T lymphocyte subsets in Sézary syndrome

The expansion of CD4+CD7- T cells in the peripheral blood of Sézary syndrome (SS) is well known. It remains unclear whether this population contains the dominant T cell clone. Peripheral blood mononuclear cells (PBMC) of five SS patients were sorted by fluorescence-activated cell sorting into CD4+CD7- and CD4+CD7+ populations. These populations were analysed separately for clonality of the T cell receptor gamma chain (TCR-gamma) by PCR-DGGE. The cytokine profile of both populations was investigated by RT-PCR ELISA for IFN-gamma, IL-2, IL-4, IL-5, IL-10, IL-13 and IL-15. In three other patients with known Vbeta-usage, the dominant T cell clones were phenotypically characterized by double staining. PCR-DGGE of TCR-gamma demonstrated that all patients had a clonal population in their blood and that this population was present in CD4+CD7- and CD4+CD7+ populations. Concerning mRNA cytokine transcription, the two populations did not show any consistent differences. In three patients with identified clones (Vbeta 3.1, 5.3 and 6.7), double staining revealed positivity for CD2, CD3, CD4, CD5, CD45RO and CD7 in a significant proportion (at least 35%). We conclude that the CD4+CD7- population does not represent the dominant T cell clone in patients with SS. An increase in this population of PBMC in SS might account for deviations in the T cell functions of the patients.

IL-12 directly up-regulates the expression of HLA class I, HLA class II and ICAM-1 on human melanoma cells: a mechanism for its antitumor activity?

IL-12 enhances cytolytic activity and proliferation of NK and T cells, and induces cytokines such as IFN-gamma. No direct effects on non-hematopoietic cells have been shown. This study investigates the effects of IL-12 on melanoma cells in vitro. We analyzed 15 melanoma cell cultures and 1 melanoma cell line. Out of 16 samples 13 expressed the beta chain of the IL-12 receptor (IL-12Rbeta). Preincubation with IL-12 increased the surface levels of human leukocyte antigen (HLA) class I, HLA class II and intercellular adhesion molecule (ICAM)-1 of those cultures with IL-12Rbeta expression. The effects of IL-12 on HLA class I could be blocked by an IL-12-neutralizing monoclonal antibody (mAb), but not by an mAb against IFN-gamma. Melanoma cells transduced with IL-12 expressed enhanced levels of HLA class I, HLA class II and ICAM-1 compared to controls. Co-incubation of the melanoma cells with allogeneic peripheral blood mononuclear cells (PBMC) resulted in enhanced proliferation and increased production of IL-2 and IFN-gamma after pretreatment with IL-12. IL-12 pretreatment increased the susceptibility of melanoma cells to lysis by prestimulated autologous PBMC. Since IL-12 induced immunocritical surface molecules on melanoma cells, it might be beneficial during immune interventions in melanoma patients.

Real time detection of photoreactivity in pharmaceutical solids and solutions with isothermal microcalorimetry

PURPOSE

In this study an irradiation cell made as an accessory for an isothermal microcalorimeter is introduced, and its suitability for detection photoreactivity in pharmaceutical solutions and solids is demonstrated. The pharmaceuticals employed are chosen as sample materials to evaluate the usefulness and stability of the irradiation cell.

METHODS

An irradiation cell has been constructed and tested in an isothermal microcalorimeter with pharmaceutical solutions and solids known to be sensitive to daylight or UV light. Light is produced with an Xe-arc lamp, split into two parts and introduced into calorimetric vessels with optical light cables. One of the vessels containing the reference sample gives the response to the heat absorbed by the material (radiant power), and the other vessel containing the sample material gives the response also to the photoreaction. The two irradiation cells are positioned in the sample sides of two separate twin microcalorimetric units.

RESULTS

Nifedipine and L-ascorbic acid were found to be photosensitive in solutions and solid states, the extent of the degradation depending on the irradiation intensity and wavelength. The threshold values of the wavelength for the photoreactions, as well as the wavelengths for the maximum reaction rates, were estimated via the scanning irradiation measurements. The ability of photons with different energies to produce heat in the photosensitive reaction of nifedipine was calculated using constant lambda measurements.

CONCLUSIONS

The technique introduced offers a rapid and versatile method to study the photosensitivity of materials in any state. In the measurements, various conditions can be simulated and thus provide information on the real behavior of materials.

Interleukin-15 is an autocrine/paracrine viability factor for cutaneous T-cell lymphoma cells

In this study we investigated the role of interleukin-15 (IL-15) in the immunobiology of cutaneous T-cell lymphoma (CTCL) cells. Using cell culture techniques, reverse transcriptase-polymerase chain reaction (RT-PCR), and immunhistochemistry we found that IL-15, like IL-7, is a growth factor for the Sézary cell line SeAx and that both cytokines prolonged the survival of malignant T cells directly isolated from Sézary syndrome (SS) patients. Both IL-15 and IL-7 were more potent than IL-2. IL-4 and IL-9, whose receptors share the same gamma chain with the receptors of IL-2, IL-7, and IL-15, did not sustain the growth of CTCL cells, indicating that signaling through the common gamma chain (gammac) is not sufficient for continuous growth. IL-13 and tumor necrosis factor-alpha (TNF-alpha) had no effect. IL-7 and IL-15 also supported the growth of SeAx cells in the presence of the apoptosis inducing agents dexamethasone and retinoic acid. The analysis of patient Sézary cells and three CTCL cell lines by RT-PCR showed that all these cells expressed IL-15 mRNA, but only a few (25%) produced IL-7 mRNA. Immunohistological analyses of skin biopsy samples of SS and Mycosis fungoides patients showed immunoreactivity for IL-15 in basal cell layer keratinocytes and in the infiltrating lymphocytes. We conclude that IL-15 is a growth or viability factor for CTCL-derived cell lines or shortly cultivated Sézary cells. The findings that IL-15 mRNA can be detected in Sézary syndrome peripheral blood mononuclear cells and that the IL-15 protein is detected in skin sections from CTCL patients suggest that IL-15 plays an important role in the biology of CTCL.

A kinetic study on crystallization of an amorphous lubricant

PURPOSE

The purpose of the work was to study the crystallization kinetics of amorphous sterotex K at different temperatures and with different methods, and to compare the obtained kinetic and thermodynamic results.

METHODS

Isothermal microcalorimetry was the principal technique to determine the crystallization behavior of sterotex K. X-ray powder diffraction and differential scanning calorimetry were employed to interpret the microcalorimetric heat flow curves and compare the kinetics and the calculated value for the transition enthalpy.

RESULTS

The best way to analyze the x-ray diffractograms was the statistic Wakelin's correlation method. The method gave consistent quantitative results with microcalorimetry and both methods showed crystallization to consist of two partially parallel part-processes, which attached probably to the different growing rates of the forms consisting of different lattice planes having the same spacing. The quantitative analysis of differential scanning calorimetry scans was troublesome to perform but the obtained average value of -51 J/g for the enthalpy of the crystallization was in good agreement with the values obtained with the other methods, the average being -52 J/g. Calculating heat flow versus released energy plots from the microcalorimetric data the crystallization mechanism was observed to change as a function of temperature.

CONCLUSIONS

A sensitive isothermal microcalorimeter can give precise and fast knowledge about possible solid state transition mechanism, but the source of the heat flow signal must be verified with other analytical methods to avoid incorrect conclusions. Due to the sensitivity and the real-time data the microcalorimetry can show up the mechanism of the transition for varying as a function of temperature and reveal the uselessness of the conventional Arrhenius relationship for extrapolations.

Interleukin-10 is a growth factor for human melanoma cells and down-regulates HLA class-I, HLA class-II and ICAM-1 molecules

IL-10 is a cytokine which shows various effects including inhibition of T-cell proliferation or HLA-dependent antigen presentation. In this study, we analysed the effects of exogenous or autocrine IL-10 on proliferation and expression of immunocritical surface molecules. Fourteen cultures of human melanoma cells were established from primary melanomas, locoregional lymph-node or distant metastases. In 5 melanoma cell cultures, proliferation in the presence of IL-10, anti-IL-10 antibodies (Ab) or control Ab was assessed with colorimetric and [3H]thymidine uptake assays. Flow cytometric analysis was used to quantify the expression of human leukocyte antigen (HLA) class-I, HLA class-II and intercellular adhesion molecule (ICAM)-1 and the IL-10 receptor (IL-10R). IL-10 production of melanoma cells was documented by RT-PCR and IL-10 protein was detected in the supernatants by means of ELISA. IL-10 enhanced proliferation and prolonged survival of melanoma cells in 5 out of 5 cultures. Anti-IL-10 Ab decreased proliferation. IL-10R expression was found in 12 out of 14 (86%) melanoma cell cultures. The expression of HLA-I, HLA-II and ICAM-1 on all melanoma cells that were positive for IL-10R showed a reduction of 10-60% by IL-10, whereas the surface levels of HLA-I, HLA-II and ICAM-1 in 5 out of 5 cell cultures revealed an increase of 10-170% by anti-IL-10 Ab. These findings suggest that IL-10 is an autocrine growth factor with significant impact on immunocritical molecules in melanoma. IL-10 effects have to be considered when planning therapeutic immunointerventions in melanoma patients.

Interleukin-10 is a growth factor for human melanoma cells and down-regulates HLA class-I, HLA class-II and ICAM-1 molecules

IL-10 is a cytokine which shows various effects including inhibition of T-cell proliferation or HLA-dependent antigen presentation. In this study, we analysed the effects of exogenous or autocrine IL-10 on proliferation and expression of immunocritical surface molecules. Fourteen cultures of human melanoma cells were established from primary melanomas, locoregional lymph-node or distant metastases. In 5 melanoma cell cultures, proliferation in the presence of IL-10, anti-IL-10 antibodies (Ab) or control Ab was assessed with colorimetric and [3H]thymidine uptake assays. Flow cytometric analysis was used to quantify the expression of human leukocyte antigen (HLA) class-I, HLA class-II and intercellular adhesion molecule (ICAM)-1 and the IL-10 receptor (IL-10R). IL-10 production of melanoma cells was documented by RT-PCR and IL-10 protein was detected in the supernatants by means of ELISA. IL-10 enhanced proliferation and prolonged survival of melanoma cells in 5 out of 5 cultures. Anti-IL-10 Ab decreased proliferation. IL-10R expression was found in 12 out of 14 (86%) melanoma cell cultures. The expression of HLA-I, HLA-II and ICAM-1 on all melanoma cells that were positive for IL-10R showed a reduction of 10-60% by IL-10, whereas the surface levels of HLA-I, HLA-II and ICAM-1 in 5 out of 5 cell cultures revealed an increase of 10-170% by anti-IL-10 Ab. These findings suggest that IL-10 is an autocrine growth factor with significant impact on immunocritical molecules in melanoma. IL-10 effects have to be considered when planning therapeutic immunointerventions in melanoma patients.

D1 dopamine receptors are not expressed in human melanoma

D1 dopamine receptor mRNA has been demonstrated in mouse melanoma cells, and the expression of these G-protein-coupled receptors in human melanoma was therefore presumed when dopamine receptor binding radiopharmaceuticals were found to be useful for the detection of metastases in whole-body scintigraphy. The aim of this study was thus to investigate if D1 dopamine receptor mRNA or protein could be directly demonstrated in melanoma cells. The presence of D1 dopamine receptor mRNA was investigated in six human melanoma cell lines from metastases using reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, in vitro binding assays with the D1 dopamine receptor agonist 125I-Sch 23982 were performed in 19 melanoma metastases. No D1 dopamine receptor mRNA could be detected by RT-PCR. All melanotic metastases were found to accumulate 125I-Sch 23982, with the presence of binding sites and intensity of 125I-Sch 23982 labelling correlating to the amount of melanin present in the metastases. Two amelanotic melanomas did not accumulate 125I-Sch 23982. D1 dopamine receptors could not be detected by means of RT-PCR or in vitro binding assays in human melanomas. Detection of antagonists is best explained by non-specific binding to melanin.

Sézary syndrome T-cell clones display T-helper 2 cytokines and express the accessory factor-1 (interferon-gamma receptor beta-chain)

Sézary syndrome (SS) is a leukemic variant of low-grade cutaneous T-cell lymphomas (CTCLs). The clonal T cells in this lymphoproliferative disorder are poorly characterized. Using antibodies against the variable region of the T-cell receptor (TCR V alpha/beta), we identified four predominant T-cell clones (two V beta 8+ clones, one V beta 5.1+, and one V alpha 2(a)+) in peripheral blood mononuclear cells (PBMC) of SS patients. Their phenotype was CD3+, CD4+, CD5+, CD45RO+. Clonal T cells were purified, and cytokine transcription and secretion was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) followed by hybridization with biotinylated probes and enzyme-linked immunosorbent assays (ELISAs). The interleukin-10 (IL-10) PCR product was cloned and sequenced and found to be identical to the published cDNA sequence. The presence of accessory factor-1 (AF-1, or interferon-gamma [IFN-gamma] receptor beta-chain) encoding mRNA was assessed by RT-PCR and immunostaining using serum of rabbits immunized with the extracellular domain of a recombinant human AF-1 protein followed by APAAP staining. Clonal T cells transcribe and secrete mainly T-helper 2 cytokines (IL-10, -5, and -13). mRNA from purified SS clones but not mRNA from SS total PBMC was positive for AF-1 in an agarose gel and/or after hybridization. AF-1 transcription was associated with membrane-bound immunoreactivity for AF-1 in SS clones. SS-derived T-cell clones display T-helper 2 cytokines. This weakens cell-mediated immunosurveillance, and explains the clinical and immunologic abnormalities in SS patients. The T-helper 2 cytokine spectrum of all clones investigated is associated with overexpression of AF-1. This suggests that AF-1 is a potential marker for these clones (and eventually other T-helper 2 lymphocytes) and might represent a target for treatment of the disease.

Role of virus and host variables in virus persistence or immunopathological disease caused by a non-cytolytic virus

C57BL/6 mice infected with increasing doses of the Armstrong isolate of lymphocytic choriomeningitis virus (LCMV) or a variant Cl 13-Armstrong, derived from LCMV-Armstrong, exhibited distinct phenotypes with respect to clearance of virus and to cytotoxic CD8+ T cell (CTL)-dependent immunopathological disease. Low (10(2) p.f.u.) and high doses (10(7) p.f.u.) of LCMV-Armstrong were cleared rapidly from immunocompetent mice. Inoculation of a high dose (10(7) p.f.u.) of LCMV Cl 13-Armstrong temporarily induced a partial deletion of the antiviral CTL precursors (CTL-p) leading to chronic infection in several organs. Although virus was cleared from most organs by day 90-150 post-infection, it persisted in the kidney. The few remaining CTL-p were able to expand and eventually clear the virus. Systemic viral titres correlated inversely with the number of CTL-p. However, in contrast LCMV-Docile injected at high dose was able to cause complete exhaustion of CTL-p resulting in long term viral persistence. LCMV-Aggressive, derived from the same parental LCMV-WE (UBC) as Docile, showed a phenotype comparable to wild-type virus. Doses of < 10(7) p.f.u. of both Armstrong virus and of Cl 13-Armstrong failed to exhaust CTL-p and caused lethal CD8+ T cell-dependent choriomeningitis and a substantial footpad swelling after local infection. By contrast, doses > 10(3) p.f.u. of LCMV-Docile failed to cause lethal choriomeningitis in C57BL/6 mice. When Cl 13-Armstrong virus (but not LCMV-Armstrong) was injected intravenously in addition to intracerebrally or into the foot, the local immunopathology was abrogated in a dose-dependent fashion. The suppression of immunopathology paralleled the extent of exhaustion of the specific CD8+ T cell response. Nucleotide sequence analysis of the viral S-RNA fragments coding for CTL epitopes in H-2b mice revealed an asparagine to serine change of amino acid 280 in the CTL epitope 275-286 of the LCMV-Docile glycoprotein (GP) in comparison to LCMV-Aggressive or wild-type WE. This change reduced overall CTL activity and thereby probably contributes to exhaustion of CTL responses in C57BL/6 (H-2b) mice. Thus, local versus systemic antigen distribution, viral characteristics and immunological parameters determine induction and exhaustion of CD8+ T cells and the course and extent of immunopathological disease.

Changes in solid-state structure of cyclophosphamide monohydrate induced by mechanical treatment and storage

The effects of mechanical treatment and various storage conditions on the structure of cyclophosphamide monohydrate were evaluated by thermal and X-ray analyses and molecular modeling. The monohydrate form of cyclophosphamide was found to convert to the anhydrous form through a metastable phase. Metastable forms were produced by mechanical treatment and by desiccation. These forms could be detected in differential scanning calometric thermograms as endothermic peaks, at approximately 39 degrees C, and X-ray powder diffractometric analysis, e.g.; by a characteristic reflection at 15.3 degrees (2 theta). Molecular modeling was used to study molecular interactions and putative metastable structures. The dehydration enthalpies of the cyclophosphamide monohydrate obtained from quantum chemical calculations and DSC analysis were 51.6 and 36.1 J/g, respectively. In a unit cell of the stable monohydrate, a water molecule is held by O(7) of the cyclophosphamide molecule and N(6)H of a neighboring cyclophosphamide molecule, with hydrogen bonds enabling existence of a water tunnel. The metastable form of cyclophosphamide is detected when a sterically formed block in the possible tunnel is removed, and the water molecules are allowed to leave the system one by one.

Resistance of lymphocytic choriomeningitis virus to alpha/beta interferon and to gamma interferon

The susceptibility to alpha/beta interferon (IFN-alpha/beta) or to gamma interferon (IFN-gamma) of various lymphocytic choriomeningitis virus (LCMV) strains was evaluated in C57BL/6 mice and in various cell lines. Anti-IFN-gamma treatment in vivo revealed that the LCMV strains Armstrong, Aggressive, and WE were most susceptible to IFN-gamma whereas Traub, Cl 13-Armstrong, and Docile were resistant. The same pattern of susceptibility to recombinant IFN-gamma was observed in vitro. In vivo treatment with anti-IFN-alpha/beta showed a sizeable increase in replication of Aggressive, Armstrong, and WE; effects were less pronounced for Docile, Cl 13-Armstrong, or Traub. Correspondingly, WE, Armstrong, and Aggressive were all relatively sensitive to purified IFN-alpha/beta in vitro, and Cl 13-Armstrong, Docile, and Traub were more resistant. Overall, there was a good correlation between the capacity of LCMV strains to establish a persistent infection in adult immunocompetent mice and their relative resistance to IFN-gamma and IFN-alpha/beta.

Peripheral clonal deletion of antiviral memory CD8+ T cells

Antiviral cytotoxic memory CD8+ T cells adoptively transferred to mice which are persistently infected with lymphocytic choriomeningitis virus WE or DOCILE initially proliferated extensively; they either caused the death of the recipient or, alternatively, disappeared within a few days. Apparently, the complete and coordinated induction and stimulation by widely distributed viral antigen caused these memory T cells to die before virus had been eliminated from the host. Thus memory T cells are as susceptible to peripheral exhaustion/deletion as unprimed T cells. These results indicate possible limitations of exclusively CD8+ T cell-mediated adoptive immunotherapy against viral infections or tumors.

[Novel possibilities for treatment of parkinsonian tremor and other abnormal movements by stimulation of the nucleus ventralis intermedius thalami]

Chronic thalamic stereotactic stimulation has been performed in 22 patients with disabling tremor and poor response to drug therapy: 17 parkinsonian tremors and 5 essential tremors. Our first results are presented with a mean follow-up of 26 months. Parkinsonian tremors 17 = complete disappearance: 12, clear improvement: 5. Essential tremors 5 = complete disappearance: 3, clear improvement: 1, failure 1 cured by thalamotomy. Choreic or ballistic dyskinesias 7 = complete disappearance: 5, clear improvements: 2. Dystonic dyskinesias 3 = complete disappearance: 2, failure: 1. This new stereotactic procedure permits to control easily not only tremor but also L-Dopa induced dyskinesias: choreic or ballistic dyskinesias and biphasic dystonic dyskinesias. The place of this surgical treatment among the other therapeutic possibilities is discussed.

Recovery of plants from cryopreserved embryogenic cell suspensions of Pinus caribaea

Embryogenic cell suspension cultures of Pinus caribaea var. hondurensis have been cryopreserved in liquid nitrogen for up to four months, using sucrose and dimethylsulfoxide as cryoprotectants. Post-thaw growth was obtained after a short lag phase. Removal of the remaining liquid around the cells using a filter disc favoured subsequent regrowth of the cells. These reestablished cultures maintained an embryogenic potential similar to non-frozen cultures. The embryos produced were able to regenerate into plants, which are now growing in a greenhouse.

Resistance to influenza virus infection of Mx transgenic mice expressing Mx protein under the control of two constitutive promoters

Transgenic mice constitutively expressing in the brain the influenza virus resistance protein Mx1 controlled by the HMG (3-hydroxy-3-methylglutaryl coenzyme A reductase) promoter showed specific resistance against the neurotropic influenza A virus strain NWS. Control mice of the A2G strain express Mx1 protein in all organs, but only after induction by interferon type I upon or without viral infection. The extent of specific resistance in transgenic mice of the best-expressing line reached about two-thirds that of controls, most likely because of considerably less total-body Mx protein activity in the transgenic mice. Thus, the theoretical advantage in these mice of the continuous presence of Mx protein with early inhibitory potential to viral replication was apparently offset by restricted organ expression. Strong evidence that the Mx1 protein on its own is a specific anti-influenza A virus agent and that its efficiency in the experimental setting is independent of interferon actions could be derived from the treatment of experimental and control mice with anti-interferon antibodies at the time of virus tests. Whereas in A2G mice, Mx1 mRNA and Mx1 protein synthesis were abolished and viral resistance was markedly reduced or abolished, resistance in the transgenic mice persisted to almost the same degree. Transgenic mice generated with a mouse albumin/Mx1 cDNA construct showed liver-specific expression. However, in two expressing transgenic lines, Mx1 protein synthesis was suppressed after a few months. The mechanism of suppression could not be elucidated, but increasing methylation of the transgene's coding region was not the cause. It is possible that continuous Mx1 protein expression in the liver is less well tolerated than that in the brain. Whether this partial suppression and, with the HMG promoter, restricted organ expression are the organism's responses to interference of Mx1 with normal cellular activities such as nucleocytoplasmic transport of RNA and proteins cannot be determined until the molecular mechanisms of antiviral activity of Mx1 protein are understood.

The causes of hospital-treated acute lower respiratory tract infection in children

OBJECTIVE

To determine the etiologic agents in children with acute lower respiratory infection.

DESIGN

A survey of a series of patients.

SETTING

General pediatric hospital serving an urban population with and without referrals in Helsinki, Finland.

PARTICIPANTS

135 Finnish children aged 2 months to 15 years (mean, 1.75 years), with clinically defined acute lower respiratory infection (with difficulty of breathing), or found to have fever and a pneumonic infiltrate on chest roentgenogram.

SELECTION PROCEDURES

Consecutive sample on voluntary basis.

INTERVENTIONS

None.

MAIN RESULTS

Of 121 children with adequate samples, an etiologic diagnosis could be established in 84 (70%): 30 (25%) had bacterial, 30 (25%) viral, and 24 (20%) mixed infections. Antibody assays alone identified the agent in 91% of positive cases.

CONCLUSIONS

Bacterial infections are common but generally underestimated in acute lower respiratory infection; serologic methods add significantly to their detection.

Serum tumor necrosis factor-alpha concentrations in children hospitalized for acute lower respiratory tract infection

Tumor necrosis factor-alpha (TNF alpha) concentrations were measured by radioimmunoassay in sera of 118 children (median age, 1.7 years; range, 2 months-15 years) hospitalized for acute lower respiratory tract infection (ALRI). Both viral and bacterial ALRI were associated with elevated concentrations of TNF alpha. Concentrations greater than 40 ng/l were seen in children with bacterial or mixed ALRI in 64% and with viral ALRI in 50% of cases. Elevated concentrations were associated with longer duration of fever before admission (P less than .05) and with a higher serum C-reactive protein concentration (P less than .05). There were no significant differences in TNF alpha concentrations between gram-positive and gram-negative infections, nor was there an association with clinical severity of ALRI. TNF alpha concentrations decreased in most patients to normal within 5 days of hospitalization, irrespective of the etiology of the infection.