title: Accumulation of Regulatory T Cells and Chronic Inflammation in the Middle Ear in a Mouse Model of Chronic Otitis Media with Effusion Induced by Combined Eustachian Tube Blockage and Nontypeable Haemophilus influenzae Infection.
abstract: Nontypeable Haemophilus influenzae (NTHi) is associated with chronic otitis media (COM). In this study, we generated a murine model of COM by using eustachian tube (ET) obstruction and NTHi (10(7) CFU) inoculation into the tympanic bulla, and we investigated the relationship between regulatory T cells (Treg) and chronic inflammation in the middle ear. Middle ear effusions (MEEs) and middle ear mucosae (MEM) were collected at days 3 and 14 and at 1 and 2 months after inoculation. Untreated mice served as controls. MEEs were used for bacterial counts and to measure the concentrations of cytokines. MEM were collected for histological evaluation and flow cytometric analysis. Inflammation of the MEM was prolonged throughout this study, and the incidence of NTHi culture-positive MEE was 38% at 2 months after inoculation. The levels of interleukin-1β (IL-β), tumor necrosis factor alpha, IL-10, and transforming growth factor β were increased in the middle ear for up to 2 months after inoculation. CD4(+) CD25(+) FoxP3(+) Treg accumulated in the middle ear, and the percentage of Treg in the MEM increased for up to 2 months after inoculation. Treg depletion induced a 99.9% reduction of bacterial counts in MEEs and also significantly reduced the ratio of NTHi culture-positive MEE. The levels of these cytokines were also reduced in MEEs. In summary, we developed a murine model of COM, and our findings indicate that Treg confer infectious tolerance to NTHi in the middle ear.
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Oita University, Oita, Japan thirano@oita-u.ac.jp suzukim@oita-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirano
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Oita University, Oita, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Kodama
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Oita University, Oita, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kawano
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Oita University, Oita, Japan thirano@oita-u.ac.jp suzukim@oita-u.ac.jp.
authors.forename: Masashi
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D004432:Ear, Middle / Q000276:immunology* / Q000473:pathology; D005064:Eustachian Tube / Q000473:pathology; D006192:Haemophilus Infections / Q000276:immunology* / Q000382:microbiology; D006193:Haemophilus influenzae / Q000276:immunology*; D007249:Inflammation / Q000276:immunology; D016753:Interleukin-10 / Q000276:immunology; D053583:Interleukin-1beta / Q000276:immunology; D018655:Lymphocyte Count; D051379:Mice; D008807:Mice, Inbred BALB C; D009092:Mucous Membrane / Q000276:immunology / Q000382:microbiology; D010034:Otitis Media with Effusion / Q000276:immunology* / Q000382:microbiology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: C556062:IL10 protein, mouse; C587672:IL1B protein, mouse; D053583:Interleukin-1beta; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10