New method to assess dilution of secretions for immunological and microbiological assays

Intersession repeatability of a novel nasal lavage technique

This study describes a novel nasal lavage method using a pediatric tracheostomy tube and examines intersession repeatability for several clinically and technically relevant parameters. Fourteen healthy subjects were included in this study. Both nasal cavities were washed using a standard amount of saline solution (7 mL) via a pediatric tracheostomy tube, and the 2 samples were pooled for measurement of cytokine concentrations and cell count. Recovery volume was also recorded. For each subject, measurements were repeated on 5 consecutive days. Intersession repeatability of recovery volume, cell count, and cytokine concentrations interleukin (IL)-6 and IL-8 were expressed in terms of mean coefficient of variation, intraclass correlation coefficient, and interitem correlations. Intraclass correlation coefficients and interitem correlation coefficients indicated almost perfect agreement for cell count and IL-8 concentrations. Recovery volume and IL-6 concentrations were more variable. The mean coefficient of variation was low for cell count (2%), IL-8 concentration (3%), and recovery volume (3%), whereas the mean percentage recovery was high (87%). This newly developed nasal lavage technique is repeatable over successive sessions for cytokine concentrations and cell counts in nasal secretions of healthy subjects. This method might be valuable in the study of inflammatory conditions involving the upper respiratory tract.

Cytolytic complement activity in otitis media with effusion

Otitis media with effusion (OME) is a chronic inflammation persisting in the middle ear cavity of at least 8 weeks duration. Middle ear effusion (MEE; n = 38), samples from children suffering from OME were investigated for their direct cytolytic activity or an ability to enhance complement lysis of unsensitized bystander cells. Thirteen of the 38 MEEs had direct endogenous haemolytic activity and 27 samples had an ability to enhance serum-initiated lysis. Using an enzyme immunoassay, high levels of terminal complement complexes (TCC) were detected in the MEE samples (mean 34.1 microg/ml, range 5--89 microg/ml). This indicated strong local complement activation that had progressed to the terminal stage. As one potential factor promoting complement activation we identified both monomeric and trimeric properdin in MEE by Western blotting. By stabilizing C3 and C5 convertases properdin accelerates the alternative and terminal pathways of complement. On the other hand, the membrane attack complex (MAC) inhibitor CD59, which was found to be extensively shed into the MEE in a functionally active form, may control excessive cytotoxicity of the MEE. In conclusion, intense complement activation, up to the terminal level, maintains ongoing inflammation in the middle ear cavity and can pose a threat to the local epithelium.

Complement C3 cleavage and cytokines interleukin-1beta and tumor necrosis factor-alpha in otitis media with effusion

OBJECTIVES

To analyze whether complement C3a anaphylatoxin, other C3 fragments, interleukin-1beta (IL-1beta), or tumor necrosis factor-alpha (TNF-alpha) contributes to inflammation in chronic otitis media with effusion (OME).

METHODS

The amount of C3a was measured by enzyme-linked immunoassay. Further breakdown of C3 was analyzed by Western blotting. IL-1beta and TNF-alpha concentrations were measured by radioimmunoassay. Bacteria were analyzed by culture and polymerase chain reaction.

RESULTS

Highly elevated levels of C3a and other C3 cleavage fragments were found in all middle ear effusion (MEE) samples. The mean values (+/- SEM, n = 26) for C3a, IL-1beta, and TNF-alpha were 5,973 +/- 1,124 ng/mL, 1,043 +/- 490 pg/mL, and 79 +/- 14.3 pg/mL, respectively. Comparison to an average C3 level of 555 (+/-108) microg/mL indicated that at least 40.5% +/- 6% of total C3 had become activated within the MEE. C3a concentrations were higher in the group in which the effusion had been present in the middle ear for a prolonged period (> or =4 mo) (P = .04). Children with multiple tube insertions had higher C3 (P = .006) and TNF-alpha (P = .04) concentrations in their MEE samples than those receiving their first tubes. C3 and C3a concentrations in MEE correlated to each other (correlation coefficient [r] = 0.513, P = .0056), as did concentrations of IL-1beta and TNF-alpha (r = 0.7016, P < .0001). No significant correlation was found between complement C3 or C3a levels and IL-1beta, TNF-alpha, or bacterial growth.

CONCLUSIONS

Highly elevated levels of C3a in MEE indicate ongoing complement activation, which is stronger than in almost any other disease demonstrated previously. Elevated C3a levels contribute to chemotactic and inflammatory potential in the MEE and correlate with the chronicity of the disease.

Quantification of cytokines and inflammatory mediators in samples of nasopharyngeal secretions with unknown dilution

In the study of inflammatory mechanisms in the upper respiratory tract, the unknown dilution of collected samples of nasal secretions poses a serious problem for interpretation of the measured concentrations of various substances in the specimens. We investigated the magnitude of the dilution problem in a true clinical research situation and determined the validity of using the levels of total protein, albumin, and secretory IgA in nasal secretions to correct for the unknown dilution. The study samples consisted of simultaneously obtained nasopharyngeal aspirates and nasal lavage specimens from 52 children with upper respiratory tract infection. The dilution factors of the nasal lavage specimens varied widely between 1.8 and 432 (median, 11.2). Of the three proteins studied, total protein had the narrowest inter-subject variation in the nasal secretions of the children and thus seemed to provide the best standardization method for comparing levels of substances between individuals. Concentrations of IL-6 standardized with total protein correlated significantly better with the true IL-6 concentrations in the nasal secretions than did IL-6 levels measured in the nasal lavage specimens without standardization (p = 0.049). These findings suggest that the most common current practice of measuring substances in nasopharyngeal specimens, i.e. measuring without correction for the dilution, may produce "false-negative" results. Potentially important information on inflammatory mechanisms may be undetected if false-negative results mask real differences between groups. The use of exogenous markers of dilution might improve the accuracy of quantifying substances in nasal secretions.

Dilution assessment of cervicovaginal secretions obtained by vaginal washing for immunological assays

Local immunological defense mechanisms in the cervicovaginal mucosa currently remain incompletely defined, especially from a quantitative point of view. Addition of an inert substance, lithium chloride (LiCl), into the washing buffer used to carry out the vaginal washing for collecting cervicovaginal secretions and measurement of its concentration with a flame absorption spectrophotometer, before and after the specimen is sampled, permits the quantification of the volume of cervicovaginal secretions collected and the approximation of the dilution factor of a soluble component introduced by the washing. Lithium, at a concentration of 10 mM, gives the best precision of measurement and has no effect on the results of the immunoassays. In a population of 27 nonpregnant women (age range, 18 to 45 years), the volume of cervicovaginal secretions collected by vaginal washing with 3 ml of LiCl-phosphate-buffered saline was 12% +/- 3.2% (mean +/- standard deviation) of the total volume and showed large interindividual variations (range, 5.6 to 18.8%); the mean dilution factor of a soluble component from the vaginal secretions was 9.9% +/- 2.8% (range, 6.3 to 18.8%). According to the date of the menstrual cycle, the mean volume of collected cervicovaginal secretions was significantly increased in the luteal phase in comparison with the follicular phase; conversely, the mean dilution factor of a soluble component was more important in the follicular than in the luteal phase. These features strengthen the need to quantify accurately the dilution factor introduced by vaginal washing when studying cervicovaginal immunity.