Inflammatory cells in mucoid effusion of secretory otitis media

Construction of an MRI-based decision tree to differentiate autoimmune and autoinflammatory inner ear disease from chronic otitis media with sensorineural hearing loss

Autoimmune and autoinflammatory inner ear diseases (AIED/AID) are characterized by the symptom of sensorineural hearing loss (SNHL). To date, standardized diagnostic tools for AIED/AID are lacking, and clinically differentiating AIED/AID from chronic otitis media (COM) with SNHL is challenging. This retrospective study aimed to construct a magnetic resonance imaging (MRI)-based decision tree using classification and regression tree (CART) analysis to distinguish AIED/AID from COM. In total, 67 patients were enrolled between January 2004 and October 2019, comprising AIED/AID (n = 18), COM (n = 24), and control groups (n = 25). All patients underwent 3 T temporal bone MRI, including post-contrast T1-weighted images (postT1WI) and post-contrast FLAIR images (postFLAIR). Two radiologists evaluated the presence of otomastoid effusion and inner ear contrast-enhancement on MRI. A CART decision tree model was constructed using MRI features to differentiate AIED/AID from COM and control groups, and diagnostic performance was analyzed. High-intensity bilateral effusion (61.1%) and inner ear enhancement (postFLAIR, 93.8%; postT1WI, 61.1%) were the most common findings in the AIED/AID group. We constructed two CART decision tree models; the first used effusion amount as the first partitioning node and postT1WI-inner ear enhancement as the second node, whereas the second comprised two partitioning nodes with the degree of postFLAIR-enhancement of the inner ear. The first and second models enabled distinction of AIED/AID from COM with high specificity (100% and 94.3%, respectively). The amount of effusion and the degree of inner ear enhancement on MRI may facilitate the distinction between AIED/AID and COM with SNHL using decision tree models, thereby contributing to early diagnosis and intervention.

Eosinophilic otitis media: CT and MRI findings and literature review

Eosinophilic otitis media (EOM) is a relatively rare, intractable, middle ear disease with extremely viscous mucoid effusion containing eosinophils. EOM is associated with adult bronchial asthma and nasal allergies. Conventional treatments for otitis media with effusion (OME) or for chronic otitis media (COM), like tympanoplasty or mastoidectomy, when performed for the treatment of EOM, can induce severe complications such as deafness. Therefore, it should be differentiated from the usual type of OME or COM. To our knowledge, the clinical and imaging findings of EOM of temporal bone are not well-known to radiologists. We report here the CT and MRI findings of two EOM cases and review the clinical and histopathologic findings of this recently described disease entity.

HIF-VEGF pathways are critical for chronic otitis media in Junbo and Jeff mouse mutants

Otitis media with effusion (OME) is the commonest cause of hearing loss in children, yet the underlying genetic pathways and mechanisms involved are incompletely understood. Ventilation of the middle ear with tympanostomy tubes is the commonest surgical procedure in children and the best treatment for chronic OME, but the mechanism by which they work remains uncertain. As hypoxia is a common feature of inflamed microenvironments, moderation of hypoxia may be a significant contributory mechanism. We have investigated the occurrence of hypoxia and hypoxia-inducible factor (HIF) mediated responses in Junbo and Jeff mouse mutant models, which develop spontaneous chronic otitis media. We found that Jeff and Junbo mice labeled in vivo with pimonidazole showed cellular hypoxia in inflammatory cells in the bulla lumen, and in Junbo the middle ear mucosa was also hypoxic. The bulla fluid inflammatory cell numbers were greater and the upregulation of inflammatory gene networks were more pronounced in Junbo than Jeff. Hif-1α gene expression was elevated in bulla fluid inflammatory cells, and there was upregulation of its target genes including Vegfa in Junbo and Jeff. We therefore investigated the effects in Junbo of small-molecule inhibitors of VEGFR signaling (PTK787, SU-11248, and BAY 43-9006) and destabilizing HIF by inhibiting its chaperone HSP90 with 17-DMAG. We found that both classes of inhibitor significantly reduced hearing loss and the occurrence of bulla fluid and that VEGFR inhibitors moderated angiogenesis and lymphangiogenesis in the inflamed middle ear mucosa. The effectiveness of HSP90 and VEGFR signaling inhibitors in suppressing OM in the Junbo model implicates HIF–mediated VEGF as playing a pivotal role in OM pathogenesis. Our analysis of the Junbo and Jeff mutants highlights the role of hypoxia and HIF–mediated pathways, and we conclude that targeting molecules in HIF–VEGF signaling pathways has therapeutic potential in the treatment of chronic OM.

Otitis media with effusion (OME) is the commonest cause of hearing loss in children, and treatment using grommets remains the commonest surgical procedure in children. Chronic forms of OM are known from human population studies to have a significant genetic component, but little is known of the underlying genes or pathways involved. We have analyzed two chronic OM mouse models, the Junbo and Jeff mutants, and have found that both demonstrate hypoxia and hypoxia-inducible factor (HIF) mediated responses. There is upregulation of inflammatory pathways in the mutant middle ears and in Junbo elevation of cytokines that modulate Hif-1α. Hif-1α levels are raised in the middle ear as well as downstream targets of HIF such as Vegfa. We explored the effects of small-molecule inhibitors of HSP90 and VEGF receptor signaling in the Junbo mutant and found significant reductions in hearing loss, the occurrence of bulla fluid, and moderation of vascular changes in the inflamed middle ear mucosa with the VEGF receptor inhibitors. The study of the Junbo and Jeff mutants demonstrates the role of hypoxia and HIF mediated pathways in OM pathogenesis, and it indicates that targeting the HIF–VEGF pathway may represent a novel approach to therapeutic intervention in chronic OM.

The role of inflammatory mediators in the pathogenesis of otitis media and sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K⁺ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

[Characteristics of migrating cells in effusion of the middle ear in patients with "eosinophilic otitis media"]

Otitis media with effusion (OME) is known to be a disease that frequently afflicts children. Recently, numerous reports of intractable OME associated with bronchial asthma have been reported, generally referred to as "eosinophilic otitis media". To comprehend the cause and pathogenesis of this disease, we conducted an electron-microscope analysis of the effusion. The subjects were 5 male and 1 female patients, 4 had aspirin-induced asthma and 2 had adult-onset asthma. The number of collapsed and intact eosinophils and other inflammatory cells in the middle ear effusion were counted, and their characteristics were reviewed. Most eosinophils in the middle ear effusion were collapsed, and a high percentage of eosinophils in the nasal discharge were also collapsed. The inflammatory cells were phagocytosed by macrophages at a high frequency in cases of otitis media with effusion, but only a low rate of phagocytosis was observed in cases with eosinophilic otitis media. It is known that necrotic cells are phagocytosed with difficulty, while apoptotic cells are phagocytosed easily by macrophages. Therefore, collapsed eosinophils persist for a long time in middle ear effusion and the released granule proteins from the eosinophils cause the tissue failure. Threfore, we believe that treatment directed at causing apoptosis of eosinophils can prevent exacerbation of the intractable inflammation in this condition.

The link between allergic rhinitis and otitis media

Past studies implicated allergy in the pathogenesis of otitis media. However, definitive proof of the assertion is lacking. Epidemiologic studies, including one recently published by Rylander and Megevand, consistently identify allergy as a risk factor for otitis media. Also, higher than expected frequencies of allergy are reported for patients with otitis media, but it is unclear if this is an epiphenomenon associated with referral bias. This possibility is exemplified by the results of two reviewed papers where Velepic and colleagues reported a 25% prevalence of allergy in otitis media patients while Alles and colleagues reported a prevalence of 89%. Other studies documented biochemical components of allergic inflammation in the effusions recovered from children with otitis media, and Hurst and colleagues published a recent paper continuing on that theme. However, it is not known if a local allergic reaction is required for the production of these components and if they are produced exclusive of other inflammatory products. Three published studies explored mechanisms by which allergy could cause otitis media. Tikkanen and colleagues reexamined at age 10 a group of 56 subjects with previously diagnosed milk allergy and showed that despite decreased reactivity to milk protein a high prevalence of otitis media was retained. This suggests that it is the allergic condition, not the specific allergy to milk that increases otitis media risk. Downs and colleagues exposed the middle ears of rats to histamine and provoked changes in the pressure regulating and clearance functions of the Eustachian tube. Those changes could prolong an otitis media episode, but middle ear histamine is not limited to the allergic condition. Gentile and colleagues challenged the nose of allergic and nonallergic subjects with histamine followed by interleukin-6 or placebo and measured nasal, pulmonary, Eustachian tube and middle ear functions. Interleukin-6 did not change the Eustachian tube or middle ear functions but did cause increased secretions in allergic patients.

Clinical characteristics of so called eosinophilic otitis media

OBJECTIVE

Although "eosinophilic otitis media" is not as uncommon a condition as was previously believed, its cause and pathogenesis are not yet fully understood. The purpose of this study was to describe the clinical characteristics in patients with "eosinophilic otitis media" to clarify its pathogenesis.

METHODS

Seven adult patients with persistent and intractable otitis media with viscous middle ear effusion containing many eosinophils, who were also under treatment for bronchial asthma, were studied. The following examinations were conducted: nasopharyngeal endoscopy, pure-tone audiometry, eustachian tube function test, temporal bone CT scan, blood analysis, bacterial and fungal culture of middle ear effusion, histological study of the middle ear and nasal specimens, and measurement of eosinophilic cationic protein (ECP) in middle ear effusion.

RESULTS

Some patients had persistent perforation with papillomatous granulation tissue arising from the mesotympanic mucosa, and all the patients had nasal polyposis. The pure-tone audiometry showed the mixed-type of hearing loss in all the patients, and the hearing level deteriorated progressively during the course in some patients. The eustachian tube function was not always poor but was patulous in some cases. The most severely diseased areas were in the eustachian tube and mesotympanum by temporal bone CT images. All the seven patients had the high levels of total serum IgE, but the RAST scores were negative in three patients and low grade in three patients. The accumulation of eosinophils was observed in middle ear effusion, middle ear mucosa and nasal polyps, and the eosinophils were highly activated with degranulation. High level of ECP was also recovered from middle ear effusion.

CONCLUSIONS

Active eosinophilic inflammation occurs in the entire respiratory tract, including the middle ear in these patients. From our present investigation, we propose the criteria and clinical characteristics of "eosinophilic otitis media".

Efficacy of an antiallergic drug on otitis media with effusion in association with allergic rhinitis. An experimental study

The effect of an antiallergic drug on the evacuation of middle ear effusion (MEE) from the tubotympanum was investigated by means of an animal model with both otitis media with effusion (OME) and allergic rhinitis. Azelastine hydrochloride (AZ), an oral antiallergic drug, was administered and the presence of MEE was investigated. Serous MEE was seen in 12 of the 13 untreated control animals on the 11th day after the experimental OME was induced, whereas MEE was detected in 9 of the 13 animals administered 1 mg/kg of AZ, but only in 4 of the 13 animals administered 2 mg/kg of AZ. In addition, the effect of AZ on MEE production was also examined in an experimental OME animal model without allergic rhinitis. Middle ear effusion was observed in all OME animals that received 2 mg/kg AZ for 5 consecutive days, before and 3 days after the experimental OME was induced. Results of the present study indicate that AZ promotes the evacuation of MEE from the tubotympanum in the OME animal model associated with nasal allergy. These data suggest that an antiallergic drug may contribute to the therapy of OME patients in association with nasal allergy indirectly, by promoting evacuation of MEE due to inhibition of type I allergic reactions in the nasopharynx.

The role of IgE-mediated immunity in otitis media: fact or fiction?

As both OME and allergic rhinitis are common among young children, these disorders are occasionally seen in the same patients. Many clinical and experimental studies have denied the allergic etiology of OME, although type I allergic reactions in the nose cause tubal obstruction without inducing MEE because the induced obstruction remains for a short duration. An animal model study demonstrated that allergy-induced tubal obstruction disturbs the clearance of MEE significantly. Since a clinical and an experimental study showed the efficacy of allergic treatment in patients or animals having both diseases, allergy and OME should be treated simultaneously in patients with both diseases. Viral infections of the upper respiratory tract induce viral-specific IgE antibodies, which may cause mucosal inflammatory reactions similar to those seen in type I allergy. Viral infection also triggers bacterial infection. Consequently, viral infection is a critical factor in the etiopathogenesis of OME.

In vitro regulation of neutrophil migration by beta 2 integrins (LFA-1 and Mac-1) in patients with otitis media

Beta 2 integrins are located on the surface of neutrophils and have important roles in cell migration to an inflammatory site. We investigated the inhibitory effect of antibodies to the beta 2 integrin family for neutrophil migration into middle ear effusion (MEE) during acute otitis media in children and chronic otitis media with effusion in both children and adults. Neutrophil migration to MEE samples was assessed in vitro in a 48-well Boyden chamber. The migration index value and the activity of chemoattractants in MEE was found to be proportional to the number of infiltrated cells. Migration of activated neutrophils into MEE was significantly inhibited by blocking surface-expressed cell adhesion molecules (CAM) with anti-CD11b (Mac-1 alpha) and anti-CD18 (common beta 2 subunit) antibodies (P < 0.001) but not with anti-CD11a (LFA-1 alpha) antibody. These inhibitory effects of anti-CAM antibodies were found in all types of MEE in all age groups studied. A new therapeutic approach to inflammation has been considered recently that utilizes inhibition of neutrophil migration with a blocking antibody to CAM. Our in vitro data support a possible therapeutic effect of anti-CAM antibody, indicating that administration of anti-CD11b and CD18 antibodies may be useful for treating human otitis media.

Cell adhesion molecules of experimental otitis media in the rat

We examined the expression of cell adhesion molecules (CAM) in immune-mediated otitis media using keyhole limpet haemocyanin (KLH) in the rat, as well as the regulation of these CAM in peripheral blood polymorphonuclear leucocytes (PMN) and lymphocytes upon exposure to middle ear effusion (MEE). After general immunization, a topical antigen was introduced into the middle ear cavity. One day after exposure, CD18+ cells, primarily PMN, had maximally invaded the middle ear mucosa and mucosal epithelium. Mucosal epithelium strongly expressed intercellular adhesion molecule-1 (ICAM-1), only on the first day. The total number of cells in MEE reached a peak on day 3. On day 3, ICAM-1+ cells had reached a peak of 24.5% of the total cells. On day 2. CD18+ cells had reached a peak at 75.3% of the total cells. We examined the regulation of CAM in peripheral blood upon exposure to MEE. The percentage of fluorescent CD18+ PMN increased with MEE compared to those incubated in its absence, but those of L-selectin-positive PMN significantly decreased CAM on the surface lymphocytes did not change when incubated with MEE. The expression of CAM (CD18, ICAM-1) appears important for the initiation of otitis media. Moreover, it was thought that the interaction between the infiltrated PMN and MEE may modify the expression of CAM during the inflammatory process in the middle ear cavity.

Biochemical evidence of platelet-activating factor (PAF) in human middle ear effusions

Platelet-activating factor (PAF) is one of the most potent biological lipid mediators. This is especially true in relation to inflammation. In order to characterize the biochemical features of otitis media with effusion, the authors characterized and determined the concentration of the PAF present in human middle ear effusions obtained from 23 patients with otitis media with effusion. Each sample of middle ear effusion was divided into two groups: serous (n = 12) and mucoid effusions (n = 11). The platelet-activating factor activity was found mainly in mucoid middle ear effusions, and the amounts of PAF were higher in mucoid type (3.55 +/- 1.19 ng/g, mean +/- standard deviation [SD]) than in the serous type (0.44 +/- 0.19 ng/g). Phospholipids obtained from the middle ear effusions contained a large amount of lyso-platelet-activating factor, the biologically inactive precursor or breakdown product of platelet-activating factor. Based on these findings, it is suggested that platelet-activating factor may play an important role as a mediator of the inflammatory responses in the pathogenesis of otitis media with effusion.

Cellular events in relation to bacteria-specific antibodies in middle ear effusion during acute otitis media

The proportions of neutrophils and lymphocytes, the total number of viable lymphocytes and their spontaneous proliferating activity as well as the proportion of B-cells were determined in 238 middle ear effusion (MEE) samples from 124 ears and in 40 serum samples of 85 children in relation to the presence of bacteria-specific antibodies in MEE and the clinical outcome of acute otitis media (AOM) during the course of AOM. The percentage of lymphocytes was higher, and that of the neutrophils lower, in the ears with bacteria-specific antibodies than in the ears with no antibodies. The higher proportion of MEE lymphocytes and the presence of antibodies correlated to the faster resolution of AOM. Moreover, the total number of viable lymphocytes and the proliferating activity of these cells were related to the presence of specific antibodies in MEE. The findings of this study underline the importance of local mucosal immunity taking place in the middle ear in connection with bacteria-specific antibodies in resting AOM.

Prostaglandin content in human middle ear effusions

The concentrations of prostaglandins (PGs) were measured by a radioimmunoassay in human middle ear effusions (MEEs) obtained from patients with otitis media with effusions. Each sample of MEE was divided into two groups: serous effusions and mucoid ones. The main PG in both the serous and mucoid effusions was TXB2 (375 and 857 pg/ml, respectively), followed by PGE2 (173 and 459 pg/ml, respectively). Smaller quantities of PGD2 (35 and 64 pg/ml, respectively), PGF2 alpha (139 and 183 pg/ml, respectively), and 6ketoPGF1 alpha (129 and 201 pg/ml, respectively) were also found in the MEEs. The amounts of each PG in the mucoid effusions were 2 or 3 times higher than those found in the serous effusions, while protein concentrations and the profile of these PGs in the MEEs were almost the same in the mucoid and serous groups. These results suggest that PGs may play an important role as a mediator of the inflammatory responses in the pathogenesis of MEEs.

Effects of middle ear effusion on neutrophil function

The neutrophil chemotactic activity of middle ear effusions (MEE) was measured in patients with pediatric chronic, adult chronic, and acute otitis media with effusion (OME). Chemotactic activity differed significantly among the three groups of otitis media in the following order: adult chronic less than pediatric chronic less than acute. Culture-positive effusions had higher chemotactic activity than did those that tested culture negative, suggesting that bacterial infection is related to neutrophil chemotactic activity. The chemotactic function of normal peripheral neutrophils was not enhanced by preincubation with MEE, but their bactericidal function was enhanced. In conclusion, bacterial infection in the middle ear is one of the major determining factors of neutrophil infiltration during OME, and MEE enhances the bactericidal function of neutrophils.

Finnish approach to the treatment of acute otitis media. Report of the Finnish Consensus Conference

The theme of the first consensus conference to be held in Finland was the treatment of acute otitis media. The statements and recommendations accepted by the conference, which was organized according to the National Institutes of Health model, are presented in this report. On the basis of scientific knowledge, clinical experience, and conditions in Finland, the conference delegates concluded that penicillin V, in large doses, is still the drug of first choice in this disease. The importance of surgical drainage of the middle ear was stressed, as was the necessity of careful follow-up of the patient until the condition is completely healed. Decongestants were considered rather useless. In the prevention of recurrent attacks, adenoidectomy but not tonsillectomy was regarded as being of help, tympanostomy of probable benefit, antimicrobial (sulfonamide) prophylaxis worth considering in selected cases, but the effect of pneumococcal vaccination poor. The conference delegates agreed that uncomplicated acute otitis media should, as before, usually be treated by physicians taking care of children at the primary health care level.

A bacteriological study of the middle ear and upper respiratory tract in children with chronic secretory otitis media

Middle ear effusions and swabs from the external auditory meatus, nasopharynx and anterior nares have been collected from 100 children with chronic secretory otitis media. Isolates of Haemophilus influenzae and Streptococcus pneumoniae were typed and in vitro sensitivities to commonly used antibiotics were determined for these species and Staphylococcus aureus. Positive middle ear cultures were obtained from 21 children (27 effusions). Haemophilus influenzae and S. pneumoniae were the commonest organisms isolated, both from the middle ear and upper respiratory tract. When one or other of these species was isolated from the middle ear, the same organism was generally found in the upper respiratory tract, but not in the ear canal. The serotypes isolated from the different sites were also the same. Type 19 was the commonest Pneumococcal serotype isolated, while type e was the commonest capsulated strain of H. influenzae. Thirty-six per cent of strains of H. influenzae were resistant to penicillin and 25% of those of S. pneumoniae were resistant to trimethaprim. Eighty-one per cent of isolates of S. aureus were penicillin resistant. There was no difference in the incidence of either S. pneumoniae or H. influenzae in the post nasal spaces of children who had had their adenoids removed and those who had not.

Inflammatory changes reflected in middle ear effusion in otitis media

Otitis media (OM) is an extremely wide-spread disease, and the presence of middle ear effusion (MEE) is a common phenomena in OM. The analyses of MEE provide important information for better understanding of etiology and evaluation of inflammatory stages of the middle ear cavity. Well investigated etiologic factors of OM have included negative pressures within the middle ear cavity secondary to Eustachian tube dysfunction, and bacterial or viral infection. It is quite conceivable that the biochemical, cytological and immunochemical products found in the middle ear mucosa (MEM) and MEE during OM may contribute to the clinical course of the disease. The sources of these inflammatory components include: inflamed epithelial cells of MEM, cells of the subepithelial space, vasogenic origins, bacterial and/or inflammatory cell products in MEE. In animal studies (serous otitis media [SOM] and purulent otitis media [POM]), interesting correlations between sequential biochemical and cytological findings have been observed. The vasodilation, increased blood vessel permeability, and the release of intracellular products both from inflamed middle ear mucosa and inflammatory cells are determining factors for the biochemical changes of MEE. Recently, the importance of the role of the subepithelial space (SES) in the pathogenesis of various types of OM has been emphasized in human studies. A strong cellular-immune response with proliferation of fibroblasts, collagen fibers, plasma cells, lymphocytes, macrophages, along with an increase in capillary networks have been characterized with SES changes in OM. Analysis of MEE by biochemical and immunochemical markers (prostaglandins, immunoglobulins, intracellular enzymes) have reflected inflammatory changes in the MEM of various types and stages of OM.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefaclor in the treatment of otitis media with effusion

A randomized clinical trial in which 91 children with chronic OME participated was performed. Cefaclor 20 mg/kg body weight b.i.d. was given to the treated group (n = 46) during 10 days preceding the day appointed for surgery. The control group (n = 45) remained untreated. On the day scheduled for surgery 24 (52%) of the treated cases had healed, compared to 5 (11%) of the untreated cases, a significant difference (p less than 0.001). The long term effects showed that in the treated group 18 of the 24 primarily healed remained unoperated at a median follow-up period of 20 months. In the untreated group two of the five that originally resolved later relapsed and were subjected to surgery.

Histamine levels in middle ear effusions

The presence of histamine in 131 middle ear effusions was determined by the fluorometric assay technique. This potent mediator of inflammation was found in significant amounts in most of the samples, suggesting that it may play an important role in the pathogenesis of otitis media with effusion. It is postulated that mast cells located in the lamina propria of the tympanic mucoperiosteum are triggered to degranulate and release histamine by anaphylatoxin derived from activation of the complement system.

Aspects of biological potentials of mononuclear cells in middle ear effusions

Mononuclear phagocytes are cells common in the subepithelial space of the mucosa of the middle ear and in middle ear effusion during an attack of otitis media. Here we review studies to date on biological potentials of aural macrophages in the pathogenesis of otitis media. The origin of aural macrophages may be in the circulating pool of monocytes in the blood, in the pre-existing population of macrophages in the mucosa of the middle ear, in proliferation of macrophages in the middle ear, or in nasopharyngeal and tonsillar tissues. Macrophages demonstrate great phagocytic activity in eliminating tissue-debris, bacteria, and viruses. It seems likely that the secretory products of macrophages--such as lysozyme, components of complement, prostaglandins, collagenase, and other biologically active agents--play an important part in the pathogenesis of otitis media. There is also evidence available that aural macrophages play an important role in the regulation of lymphocytic response to antigens in active otitis media.