Immune responses of adenoidal lymphocytes specific to Haemophilus influenzae in the nasopharynx.

<bold>Objectives: </bold>Investigate immune responses of adenoidal lymphocytes against outer-membrane protein P6 purified from nontypeable Haemophilus influenzae (HI). Clarify the role of adenoids in regulating the colonization of HI in the nasopharynx.<bold>Study Design: </bold>Microbiological and immunological examinations of adenoids obtained from 21 children, 15 boys and five girls, from 1 to 13 years of age (median, 5 y), suffering from adenoidal hypertrophy complicated by otitis media with effusion (OME).<bold>Methods: </bold>The incidence of HI in adenoids was compared with the number of P6-specific immunoglobulin (Ig) A-secreting cells in adenoids, determined by enzyme-linked immunoassay.<bold>Results: </bold>Quantitative culture assay showed significant correlation between the numbers of HI in adenoids and those in nasopharyngeal secretions (NS). In children aged 5 years and younger, the numbers of P6-specific IgA-secreting cells in adenoids were significantly correlated with IgA antibody titers in NS (r = 0.68, P < .05). The numbers of P6-specific IgG- and IgA-secreting cells were lower in children aged 6 years and older than in children aged 5 years and younger. Furthermore, the number of P6-specific IgA-secreting cells was significantly increased in HI-negative subjects when compared with HI-positive subjects (P < .05).<bold>Conclusions: </bold>Adenoids play an important role as an effector site of the mucosal immune system in the upper respiratory tract. IgA immune responses in adenoids are responsible for the clearance of HI from the nasopharynx. [ABSTRACT FROM AUTHOR]