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

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).

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.

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.

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.