Mucosal Immune Responses of the Nasopharynx and Tonsils in Response to Bacterial Infection

Abstract

Adenoids and palatine tonsils are known to function as nasopharyngeal-associated lymphoreticular tissue for mucosal immune responses in the upper aerodigestive tract. In the present study, we investigated the immune responses of tonsillar lymphocytes in response to nontypeable Haemophilus influenzae (NTHi). Adenoids, palatine tonsils and nasopharyngeal secretions were obtained from patients who had undergone adenoidectomy or palatine tonsillectomy, and the numbers of NTHi in the samples were quantitated. The antibody activities against P6, one of the outer membrane proteins of NTHi, were determined by ELISA and the numbers of P6-specific antibody-producing cells were determined by ELISPOT. Production of cytokines from CD4⁺ T cells incubated with P6 was determined by ELISA and RT PCR. The results showed an increase of P6-specific IgA antibody activity and a decrease of NTHi in nasopharyngeal secretions with older age. The numbers of NTHi in the adenoids and the palatine tonsils decreased in samples having a large number of P6-specific IgA antibody-producing cells. CD4⁺ T cells more frequently produced Th2 type cytokines than Th1 type cytokines. The findings suggest that the adenoids and the palatine tonsils play an important role in regulating mucosal immune responses and the colonization of NTHi in the nasopharynx.