Otitis Media: Immunosuppressive and Pro-Inflammatory Lymphocytes Strike a Balance Between Bacterial Colonization and Mucosal Inflammation

Andrew W. Taylor-Robinson

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

Abstract

Otitis media, inflammation of the middle ear, is a major cause of pain and impaired auditory acuity in children. Recurrent episodes may hinder development of speech, learning and social behaviour. The presence of the bacteria Streptococcus pneumoniae, non-typeable Haemophilus influenzae and Moraxella catarrhalis is often implicated. These three species colonize the nasopharynx asymptomatically but host tolerance of high nasopharyngeal load contributes to onset of inflammation. Immunosuppression is evident in susceptible children which may contribute to tolerance and hence to progression to chronic disease. While the causative factors involved in the immunosuppressive response are currently unknown, evidence from other mucosal sites indicates that a subset of T helper (TH) lymphocytes, T regulatory (Treg) lymphocytes, contribute to regulation of immunosuppression to commensal bacteria and promote advancement of infection. The principal function of Treg lymphocytes is induction of immune tolerance through immunosuppression in the periphery to self and foreign and antigens. They have been identified in adenoids and tonsils and are recognised to have a positive association with pneumococcus nasopharyngeal colonization. Of note, the pro-inflammatory TH17 lymphocyte response to S. pneumoniae is reduced in pneumococcalpositive children. Moreover, inadequate T lymphocyte proliferation to non-typeable H. influenzae is evident in otitis media-prone children. A restricted T lymphocyte repertoire in young children may explain high nasopharyngeal bacterial carriage observed in this population. Yet, TH17 and TH1 lymphocyte responses may be reduced due to Treg lymphocyte suppression. As discussed in this chapter, the immune factors regulating nasopharyngeal colonization are not characterized clearly. Further research is needed to establish how host immunity underpins development of otitis media.

Original languageEnglish
Title of host publicationAdvances in Health and Disease. Volume 45
EditorsLowell T. Duncan
Place of PublicationHauppauge, NY
PublisherNova Science Publishers, Inc.
Chapter3
Pages135-185
Number of pages51
Volume45
Edition1
ISBN (Electronic)9781685072186
DOIs
Publication statusPublished - 1 Jan 2021

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