Effect of Alloiococcus otitidis and three pathogens of otitis media in production of interleukin-12 by human monocyte cell line

Alloiococcus otitidis is detected in middle ear effusion of otitis media wi th effusion (OME). Only a limited number of studies are available concernin g the immunological profile of A. otitidis. We have studied the ability of A. otitidis and three other representative pathogens of otitis media to sti mulate the production of interleukin-12 (IL-12) from a monocytic cell line THP-1. Viable A. otitidis induced the production of IL-12 in THP-1 cells bu t IL-12 production was reduced if glutaraldehyde-fixed bacteria were used a s stimulants. When viable bacteria were physically separated from THP-1 cel ls during the stimulation period, remarkable reductions of IL-12 secretion were shown after challenge with Sram-positive bacteria A. otitidis and S. p neumoniae. When stimulated with soluble extracts of A. otitidis, THP-I secr eted IL-12 in a dose-dependent manner. The subfraction with a molecular mas s over 100 kDa showed a strong ability to induce IL-12 production. Our resu lts show that A. otitidis has immunostimulatory capacity with regard to IL- 12 production. We also show that soluble antigen(s) of A. otitidis can modu late the immune response in OME. (C) 2000 Federation of European Microbiolo gical Societies. Published by Elsevier Science B.V. All rights reserved.