Functional morphology of the mucosa of the middle ear and Eustachian tube

Genome-wide association study indicates novel associations of annexin A13 to secretory and GAS2L2 with mucous otitis media

To evaluate the genetics of chronic nonsuppurative otitis media (OM). We performed a genome-wide association study of 429,599 individuals included in the FinnGen study using three different case definitions: combined chronic nonsuppurative OM (7034 cases) (included serous and mucous chronic OM), mucous chronic OM (5953 cases), and secretory chronic OM (1689 cases). Individuals without otitis media were used as controls (417,745 controls). We used immunohistochemistry (IHC) of the murine middle ear to evaluate the expression of annexin A13. Four loci were significantly associated (p < 1.7 × 10-8) with nonsuppurative OM. Three out of the four association signals included missense variants in genes that may play a role in otitis media pathobiology. According to our subtype-specific analyses, one novel locus, located near ANXA13, was associated with secretory OM. Three loci (near TNFRSF13B, GAS2L2, and TBX1) were associated with mucous OM. Immunohistochemistry of murine middle ear samples revealed annexin A13 expression at the apical pole of the Eustachian tube epithelium as well as variable intensity of the secretory cells of the glandular structure in proximity to the Eustachian tube. We demonstrated that secretory and mucous OM have distinct and shared genetic associations. The association of GAS2L2 with ciliary epithelium function and the pathogenesis of dysfunctional mucosa in mucous OM is suggested. The abundant expression of annexin A13 in the Eustachian tube epithelium, along with its role in apical transport for the binding and transfer of phospholipids, indicates the role of annexin A13 and phospholipids in Eustachian tube dysfunction.

NLRP3 Inflammasome Activation During Acute Negative Pressure Injury in the Middle Ear of Mice

HYPOTHESIS

The present study was conducted to explore the role of the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome in mouse otic barotrauma models.

BACKGROUND

Previous studies suggest that the NLRP3 inflammasome plays an important role in the pathogenesis of middle ear disease. However, whether middle ear negative pressure injury underlies NLRP3 inflammasome activation remains unclear.

METHODS

Wild-type and Nlrp3 -/- mice were randomly assigned to control and pressure injury groups, respectively. Pressure loading was performed using a pressure cabin with the pressure level set to 20 kPa higher than that of the ambient atmosphere. This was achieved in approximately 15 seconds and maintained for 10 minutes. Hematoxylin and eosin staining was performed to detect morphological changes of the middle ear mucosa, tissue IL-1β was measured via an enzyme-linked immunosorbent assay, and cleaved caspase-1 was detected by Western blot.

RESULTS

We found that the maturation of caspase-1 and IL-1β production in the middle ear significantly increased after otic barotrauma. In Nlrp3 -/- mice, inflammasome activation is downregulated and mucosal hyperplasia is reduced compared with those of wild-type mice during recovery.

CONCLUSION

The NLRP3 inflammasome likely plays an important role in the pathogenesis of otic barotrauma. Controlling activation of the NLRP3 inflammasome may promote middle ear recovery after negative pressure injury.

HB-EGF Plays a Pivotal Role in Mucosal Hyperplasia During Otitis Media Induced by a Viral Analog

Otitis media (OM), the most common childhood illness, can be caused by bacterial and/or viral infection. Hyperplasia of the middle ear (ME) mucosa is an important component of OM that contributes to its deleterious sequelae. Our previous research revealed that ME mucosal hyperplasia in bacterially induced OM was associated with expression of the heparin-binding epidermal growth factor (HB-EGF) gene, and that HB-EGF induced the proliferation of ME mucosal explants in culture. We used single-cell RNA-Seq to identify ME cells that express Hbegf and related genes involved in mediating responses to this factor. To determine the degree to which a viral infection might induce mucosal hyperplasia, and to assess the role of HB-EGF in hyperplasia in vivo, we used, Poly(I:C) to simulate a ME viral infection, Western blotting to confirm ME protein expression, and a specific inhibitor to block the effects of HB-EGF during OM. Genes for HB-EGF and its receptor were expressed in the ME primarily by epithelial, stromal and endothelial cells. Poly(I:C) induced prominent ME mucosal hyperplasia, peaking two days after ME injection. Immunostaining revealed that cleavage of proHB-EGF into its soluble form (sHB-EGF) was strongly induced in response to Poly(I:C). Inhibition of the sHB-EGF receptor dramatically reduced the hyperplastic response of the mucosa. The results demonstrate that a synthetic analog of viral double-stranded RNA interaction can induce OM including a strong proliferative response of the ME mucosa, independent of bacteria. They also indicate that HB-EGF is the dominant growth factor responsible for ME mucosal hyperplasia in vivo.

Cochlear Immune Response in Presbyacusis: a Focus on Dysregulation of Macrophage Activity

Age-related hearing loss, or presbyacusis, is a prominent chronic degenerative disorder that affects many older people. Based on presbyacusis pathology, the degeneration occurs in both sensory and non-sensory cells, along with changes in the cochlear microenvironment. The progression of age-related neurodegenerative diseases is associated with an altered microenvironment that reflects chronic inflammatory signaling. Under these conditions, resident and recruited immune cells, such as microglia/macrophages, have aberrant activity that contributes to chronic neuroinflammation and neural cell degeneration. Recently, researchers identified and characterized macrophages in human cochleae (including those from older donors). Along with the age-related changes in cochlear macrophages in animal models, these studies revealed that macrophages, an underappreciated group of immune cells, may play a critical role in maintaining the functional integrity of the cochlea. Although several studies deciphered the molecular mechanisms that regulate microglia/macrophage dysfunction in multiple neurodegenerative diseases, limited studies have assessed the mechanisms underlying macrophage dysfunction in aged cochleae. In this review, we highlight the age-related changes in cochlear macrophage activities in mouse and human temporal bones. We focus on how complement dysregulation and the nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 inflammasome could affect macrophage activity in the aged peripheral auditory system. By understanding the molecular mechanisms that underlie these regulatory systems, we may uncover therapeutic strategies to treat presbyacusis and other forms of sensorineural hearing loss.

Innate Immunity in the Middle Ear Mucosa

Otitis media (OM) encompasses a spectrum of clinical presentations ranging from the readily identifiable Acute OM (AOM), which is characterised by otalgia and fever, to chronic otitis media with effusion (COME) where impaired hearing due to middle ear effusion may be the only clinical symptom. Chronic suppurative OM (CSOM) presents as a more severe form of OM, involving perforation of the tympanic membrane. The pathogenesis of OM in these varied clinical presentations is unclear but activation of the innate inflammatory responses to viral and/or bacterial infection of the upper respiratory tract performs an integral role. This localised inflammatory response can persist even after pathogens are cleared from the middle ear, eustachian tubes and, in the case of respiratory viruses, even the nasal compartment. Children prone to OM may experience an over exuberant inflammatory response that underlies the development of chronic forms of OM and their sequelae, including hearing impairment. Treatments for chronic effusive forms of OM are limited, with current therapeutic guidelines recommending a "watch and wait" strategy rather than active treatment with antibiotics, corticosteroids or other anti-inflammatory drugs. Overall, there is a clear need for more targeted and effective treatments that either prevent or reduce the hyper-inflammatory response associated with chronic forms of OM. Improved treatment options rely upon an in-depth understanding of OM pathogenesis, particularly the role of the host innate immune response during acute OM. In this paper, we review the current literature regarding the innate immune response within the middle ear to bacterial and viral otopathogens alone, and as co-infections. This is an important consideration, as the role of respiratory viruses as primary pathogens in OM is not yet fully understood. Furthermore, increased reporting from PCR-based diagnostics, indicates that viral/bacterial co-infections in the middle ear are more common than bacterial infections alone. Increasingly, the mechanisms by which viral/bacterial co-infections may drive or maintain complex innate immune responses and inflammation during OM as a chronic response require investigation. Improved understanding of the pathogenesis of chronic OM, including host innate immune response within the middle ear is vital for development of improved diagnostic and treatment options for our children.

Histopathology of the Mucosa of Eustachian Tube Orifice at the Middle Ear in Chronic Otitis Media With Effusion: Possible Insight Into Tuboplasty Failure

INTRODUCTION

Balloon dilation of the cartilaginous segment of the Eustachian tube has emerged as a means to directly augment tubal dilatory function, and this has been applied as a potential treatment for otitis media with effusion (OME). Although results of clinical studies involving this modality appear promising, there are still a moderate number of ears affected by OME that do not respond. The purpose of this study was to investigate the status of mucosa of the Eustachian tube at the middle ear orifice in OME as it may relate to some cases of tuboplasty failure.

METHODS

Twenty-three temporal bone specimens with OME were identified within an institutional archived collection. Each specimen was inspected for the presence of a fixed obstruction at the level of the Eustachian tube orifice at the protympanum. In addition, the mucosa at the tubal orifice was graded on a 4-point scale.

RESULTS

Overall, 3 cases (13%) were normal (Grade 1), 6 cases (26%) were mildly thickened (Grade 2), 11 (48%) were severely thickened (Grade 3), and 3 (13%) were severely thickened with polypoid degeneration (Grade 4). A single case was noted to have a complete fixed obstruction in the form of a mucosal web.

CONCLUSION

In ears affected by OME, the mucosa of the Eustachian tubal orifice at the middle ear is most often severely thickened. Normal mucosa, mucosa with severe polypoid changes, or a complete fixed obstruction are possible but uncommon. The majority of specimens studied had sufficiently diseased mucosa to raise questions regarding whether thickened mucosa in the tubal orifice may act as a barrier to middle ear ventilation that would not be directly addressed by cartilaginous Eustachian tube balloon dilation.

Genome-wide association and HLA region fine-mapping studies identify susceptibility loci for multiple common infections

Infectious diseases have a profound impact on our health and many studies suggest that host genetics play a major role in the pathogenesis of most of them. We perform 23 genome-wide association studies for common infections and infection-associated procedures, including chickenpox, shingles, cold sores, mononucleosis, mumps, hepatitis B, plantar warts, positive tuberculosis test results, strep throat, scarlet fever, pneumonia, bacterial meningitis, yeast infections, urinary tract infections, tonsillectomy, childhood ear infections, myringotomy, measles, hepatitis A, rheumatic fever, common colds, rubella and chronic sinus infection, in over 200,000 individuals of European ancestry. We detect 59 genome-wide significant (P < 5 × 10⁻⁸) associations in genes with key roles in immunity and embryonic development. We apply fine-mapping analysis to dissect associations in the human leukocyte antigen region, which suggests important roles of specific amino acid polymorphisms in the antigen-binding clefts. Our findings provide an important step toward dissecting the host genetic architecture of response to common infections.

Susceptibility to infectious diseases is, among others, influenced by the genetic landscape of the host. Here, Tian and colleagues perform genome-wide association studies for 23 common infections and find 59 risk loci for 17 of these, both within the HLA region and non-HLA loci.

Cilia distribution and polarity in the epithelial lining of the mouse middle ear cavity

The middle ear conducts sound to the cochlea for hearing. Otitis media (OM) is the most common illness in childhood. Moreover, chronic OM with effusion (COME) is the leading cause of conductive hearing loss. Clinically, COME is highly associated with Primary Ciliary Dyskinesia, implicating significant contributions of cilia dysfunction to COME. The understanding of middle ear cilia properties that are critical to OM susceptibility, however, is limited. Here, we confirmed the presence of a ciliated region near the Eustachian tube orifice at the ventral region of the middle ear cavity, consisting mostly of a lumen layer of multi-ciliated and a layer of Keratin-5-positive basal cells. We also found that the motile cilia are polarized coordinately and display a planar cell polarity. Surprisingly, we also found a region of multi-ciliated cells that line the posterior dorsal pole of the middle ear cavity which was previously thought to contain only non-ciliated cells. Our study provided a more complete understanding of cilia distribution and revealed for the first time coordinated polarity of cilia in the epithelium of the mammalian middle ear, thus illustrating novel structural features that are likely critical for middle ear functions and related to OM susceptibility.

Anti CD163+, Iba1+, and CD68+ Cells in the Adult Human Inner Ear: Normal Distribution of an Unappreciated Class of Macrophages/Microglia and Implications for Inflammatory Otopathology in Humans

HYPOTHESIS

Identification, characterization, and location of cells involved in the innate immune defense system of the human inner ear may lead to a better understanding of many otologic diseases and new treatments for hearing and balance-related disorders.

BACKGROUND

Many otologic disorders are thought to have, as part of their disease process, an immune component. Although resident macrophages are known to exist in the mouse inner ear, the innate immune cells in the human inner ear are, to date, unknown.

METHODS

Primary antibodies against CD163, Iba1, and CD68 (markers known to be specific for macrophages/microglia) were used to immunohistochemically stain celloidin embedded archival temporal bone tissue of normal individuals with no known otologic disorders other than changes associated with age.

RESULTS

Cells were positively stained throughout the temporal bone within the connective tissue and supporting cells with all three markers. They were often associated with neurons and on occasion entered the sensory cell areas of the auditory and vestibular epithelium.

CONCLUSIONS

We have immunohistochemically identified an unappreciated class of cells in the normal adult inner ear consistent in staining characteristics and morphology with macrophages/microglia. As in other organ systems, it is likely these cells play an essential role in organ homeostasis that has not yet been elucidated within the ear.

Autologous human nasal epithelial cell sheet using temperature-responsive culture insert for transplantation after middle ear surgery

Postoperative mucosal regeneration of the middle ear cavity and the mastoid cavity is of great importance after middle ear surgery. However, the epithelialization of the mucosa in the middle ear is retarded because chronic inflammation without epithelialization aggravates gas exchange and clinical function. These environmental conditions in the middle ear lead to postoperative retraction and adhesion of the newly-formed tympanic membrane. Therefore, if the mucosa on the exposed middle ear bone surface can be rapidly regenerated after surgery, the surgical treatments for cholesteatoma and adhesive middle ear disease can potentially be improved. In this study, we successfully generated a cell sheet designed for the postoperative treatment of cholesteatoma. We used nasal cells to create an artificial middle ear mucosal cell sheet with a three-dimensional (3D) configuration similar to that of the middle ear mucosa. The sheets consisted of multi-layered mucosal epithelia and lower connective tissue and were similar to normal middle ear mucosa. This result indicates that tissue-engineered mucosal cell sheets would be useful to minimize complications after surgical operations in the middle ear and future clinical applications are expected. Copyright © 2015 John Wiley & Sons, Ltd.

Middle Ear and Eustachian Tube Mucosal Immunology

Mucosal immune responses within the middle ear and eustachian tube generally provide an effective and efficient response to the presence of microbial pathogens, with approximately 80% of clinically recognizable middle ear infections resolved within 7 days. Particularly for young children aged less than 3 years of age, the proximity and direct connection of the middle ear, via the eustachian tube, to the nasopharynx provide increased risk of commensal bacteria and upper respiratory tract viruses infecting the middle ear. Mucosal immunological defense in the middle ear and eustachian tube utilizes a number of mechanisms, including physicochemical barriers of mucus and the mucosal epithelial cells and innate immune responses such as inflammation, cellular infiltration, effusion, and antimicrobial protein secretions, in addition to adaptive host immune responses. Recent advances in otopathogen recognition via microbial pattern recognition receptors and elucidation of complex signaling cascades have improved understanding of the coordination and regulation of the middle ear mucosal response. These advances support vaccine development aiming to reduce the risk of otitis media in children.

Morphology and ciliary motion of mucosa in the Eustachian tube of neonatal and adult gerbils

The Eustachian tube is a small canal that connects the tympanic cavity with the nasal part of the pharynx. The epithelial lining of the Eustachian tube contains a ciliated columnar epithelium at the tympanic cavity and a pseudostratified, ciliated columnar epithelium with goblet cells near the pharynx. The tube serves to equalize air pressure across the eardrum and drains mucus away from the middle ear into the nasopharynx. Blockage of the Eustachian tube is the most common cause of all forms of otitis media, which is common in children. In the present study, we examined the epithelial lining of the Eustachian tube in neonatal and adult gerbils, with a focus on the morphological and functional development of ciliated cells in the mucosa. The length of the tube is ∼8.8 mm in adult gerbils. Scanning electron microscopy showed that the mucosal member near the pharyngeal side contains a higher density of ciliated cells and goblet cells than that near the tympanic side. The cilia beat frequency is 11 Hz. During development, the length of the Eustachian tube increased significantly between postnatal day 1 (P1) and P18. Scanning electron microscopy showed that the mucosa contained a high density of ciliated cells with a few goblet cells at P1. The density of ciliated cells decreased while the density of goblet cells increased during development. At P18, the mucosa appeared to be adult-like. Interestingly, the ciliary beat frequency measured from ciliated cells at P1 was not statistically different from that measured from adult animals. Our study suggests that the Eustachian tube undergoes significant anatomical and histological changes between P1 and P18. The tube is morphologically and functionally mature at P18, when the auditory function (sensitivity and frequency selectivity) is mature in this species.

Otitis media as a presenting complaint in childhood immunodeficiency diseases

Otitis media is one of the most common childhood infections and may result from a variety of underlying problems. Suspicion of immunodeficiency should increase when ear infections are frequent; suppurative; unresponsive to antibiotics; caused by unusual organisms; or seen in the context of other frequent infections, severe eczema, or failure to thrive. Humoral immune deficiencies, particularly with an inability to make antibody to encapsulated organisms, are the immunodeficiencies most likely to cause increased otitis media. Immune system evaluation should concentrate on humoral immunodeficiency disorders, but the presenting history and physical findings also should be considered when designing the work-up. Treating the underlying immune deficiency is usually necessary to adequately control the ear infections.

Induction of beta defensin 2 by NTHi requires TLR2 mediated MyD88 and IRAK-TRAF6-p38MAPK signaling pathway in human middle ear epithelial cells

Background

All mucosal epithelia, including those of the tubotympanium, are secreting a variety of antimicrobial innate immune molecules (AIIMs). In our previous study, we showed the bactericidal/bacteriostatic functions of AIIMs against various otitis media pathogens. Among the AIIMs, human β-defensin 2 is the most potent molecule and is inducible by exposure to inflammatory stimuli such as bacterial components or proinflammatory cytokines. Even though the β-defensin 2 is an important AIIM, the induction mechanism of this molecule has not been clearly established. We believe that this report is the first attempt to elucidate NTHi induced β-defensin expression in airway mucosa, which includes the middle ear.

Methods

Monoclonal antibody blocking method was employed in monitoring the TLR-dependent NTHi response. Two gene knock down methods – dominant negative (DN) plasmid and small interfering RNA (siRNA) – were employed to detect and confirm the involvement of several key genes in the signaling cascade resulting from the NTHi stimulated β-defensin 2 expression in human middle ear epithelial cell (HMEEC-1). The student's t-test was used for the statistical analysis of the data.

Results

The experimental results showed that the major NTHi-specific receptor in HMEEC-1 is the Toll-like receptor 2 (TLR2). Furthermore, recognition of NTHi component(s)/ligand(s) by TLR2, activated the Toll/IL-1 receptor (TIR)-MyD88-IRAK1-TRAF6-MKK3/6-p38 MAPK signal transduction pathway, ultimately leading to the induction of β-defensin 2.

Conclusion

This study found that the induction of β-defensin 2 is highest in whole cell lysate (WCL) preparations of NTHi, suggesting that the ligand(s) responsible for this up-regulation may be soluble macromolecule(s). We also found that this induction takes place through the TLR2 dependent MyD88-IRAK1-TRAF6-p38 MAPK pathway, with the primary response occurring within the first hour of stimulation. In combination with our previous studies showing that IL-1α-induced β-defensin 2 expression takes place through a MyD88-independent Raf-MEK1/2-ERK MAPK pathway, we found that both signaling cascades act synergistically to up-regulate β-defensin 2 levels. We propose that this confers an essential evolutionary advantage to the cells in coping with infections and may serve to amplify the innate immune response through paracrine signaling.

The role of Fas-mediated apoptosis in otitis media: observations in the lpr/lpr mouse

Apoptosis, or programmed cell death, is a critical regulatory mechanism involved in the function, homeostasis and stimulus response of many organ systems. In the middle ear, apoptosis could participate in mucosal remodeling or leukocyte clearance during otitis media (OM). Fas is a death receptor that can contribute to apoptosis in a variety of cell types. To assess the role of Fas signaling in OM, we probed for expression of Fas and Fas ligand (FasL) by polymerase chain reaction (PCR) during bacterial OM in the rat. In addition, we assessed the response of the middle ear to endotoxin, an inflammatory bacterial product that has been used as a model for otitis media in the mouse, in normal and Fas deficient mice. We saw evidence of increased expression of Fas and Fas ligand during bacterial OM. Moreover, the intensity of the mucosal response to endotoxin was significantly greater and the resolution of the response was prolonged in Fas deficient mice. Prolonged resolution of mucosal hyperplasia may reflect reduced apoptosis of the hyperplastic mucosal cells. Elucidation of the pathways that regulate the mucosal hyperplastic response during otitis media brings us closer to manipulating them in the interest of reducing the chronic complications of this disease.

Radiopaque contrast dye in nasopharynx reaches the middle ear during swallowing and/or yawning

CONCLUSION

Contrast dye in the nasopharynx reaches the middle ear during swallowing and yawning in normal adults. This suggests that displacement of bacteria in nasopharyngeal secretion to the middle ear may occur frequently during sleep.

OBJECTIVE

The middle ear is sterile under normal conditions. The purpose of this study was to examine by means of CT whether radiopaque contrast dye in the nasopharynx would reflux into the middle ear of normal adults during swallowing and/or yawning.

MATERIAL AND METHODS

Six normal adult volunteers were studied. Contrast dye was kept at the orifices of the Eustachian tube during swallowing and/or yawning by placing volunteers in either a head-down or lateral decubitus position. Reflux was determined by the presence of contrast dye in the middle ear on CT scanning of the temporal bone.

RESULTS

Two of the three volunteers in each group (four out of six in total) had contrast material detected in one or both middle ear cavities.

Antimicrobial activity of innate immune molecules against Streptococcus pneumoniae, Moraxella catarrhalis and nontypeable Haemophilus influenzae

Background

Despite its direct connection to the nasopharynx which harbors otitis media pathogens as part of its normal flora, the middle ear cavity is kept free of these bacteria by as yet unknown mechanisms. Respiratory mucosal epithelia, including those of the middle ear and eustachian tube, secrete antimicrobial effectors including lysozyme, lactoferrin and β defensins-1 and -2. To elucidate the role of these innate immune molecules in the normal defense and maintenance of sterility of respiratory mucosa such as that of the middle ear, we assessed their effect on the respiratory pathogens nontypeable Haemophilus influenzae (NTHi) 12, Moraxella catarrhalis 035E, and Streptococcus pneumoniae 3, and 6B.

Methods

Two assay methods, the radial assay and the liquid broth assay, were employed for testing the antimicrobial activity of the molecules. This was done in order to minimize the possibility that the observed effects were artifacts of any single assay system employed. Also, transmission electron microscopy (TEM) was employed to evaluate the effect of antimicrobial innate immune molecules on OM pathogens. For the statistical analysis of the data, Student's t-test was performed.

Results

Results of the radial diffusion assay showed that β defensin-2 was active against all four OM pathogens tested, while treatment with β defensin-1 appeared to only affect M. catarrhalis. The radial assay results also showed that lysozyme was quite effective against S. pneumoniae 3 and 6B and was partially bacteriostatic/bactericidal against M. catarrhalis. Lysozyme however, appeared not to affect the growth of NTHi. Thus, lysozyme seems to have a more pronounced impact on the growth of the Gram-positive S. pneumoniae as compared to that of Gram-negative pathogens. Lactoferrin on the other hand, enhanced the growth of the bacteria tested. The results of the radial assays were confirmed using liquid broth assays for antimicrobial activity, and showed that lysozyme and β defensin-2 could act synergistically against S. pneumoniae 6B. Moreover, in the liquid broth assay, β defensin-1 showed a modest inhibitory effect on the growth of S. pneumoniae 6B. As assessed by ultrastructural analysis, lysozyme and β defensin-2, and to a much lesser extent, β defensin-1, appeared to be able to cause damage to the bacterial membranes.

Conclusions

Here we report that lysozyme and the β defensins can inhibit the growth of clinical isolates of otitis media pathogens – namely NTHi strain 12, S. pneumoniae strains 3 and 6B and M. catarrhalis strain 035E – and cause ultrastructural damage to these pathogens. Moreover, we demonstrate that lysozyme and β defensin-2 can act synergistically against S. pneumoniae. These findings are consistent with the concept that secreted antimicrobial peptides and other components of innate immunity constitute the first line of defense protecting host mucosal surfaces, including the tubotympanal (eustachian tube and middle ear cavity) mucosa, against pathogens.

Growth factors and their receptors in the middle ear mucosa during otitis media

OBJECTIVE

The hyperplastic response of the middle ear mucosa during bacterial otitis media is thought to be mediated by the actions of growth factors and their respective receptors. The purpose of the study was to explore the expression of growth factors known to stimulate epithelial cells in other systems, as well as their receptors, in the middle ear mucosa during otitis media.

STUDY DESIGN

Expression of mRNA growth factors and receptors was measured over time after inoculation of the rat middle ear with bacteria.

METHODS

The middle ears of 12 male Sprague-Dawley rats were injected with 10(5)/mL Haemophilus influenzae strain 3655 (nontypeable, biotype II). Three rats were killed at 6, 24, 48, and 72 hours. Three untreated rats were also killed to serve as negative controls. The middle ear mucosa samples were surgically removed and homogenized. Reverse transcription-polymerase chain reaction was performed on each sample with primers for rat epidermal growth factor, epidermal growth factor receptor (ErbB), heparin binding epidermal-like growth factor, hepatocyte growth factor, hepatocyte growth factor receptor, keratinocyte growth factor, betacellulin, amphiregulin, and neuregulin-alpha.

RESULTS

Hepatocyte growth factor and epidermal growth factor receptor primers demonstrated polymerase chain reaction products of the expected size that were not displayed in the normal middle ear mucosa. Keratinocyte growth factor and hepatocyte growth factor receptor demonstrated polymerase chain reaction products at all time points tested. Betacellulin and neuregulin-alpha products were present at all time points except 72 hours after infection.

CONCLUSIONS

The results of the study support a role for growth factors in the middle ear mucosa during otitis media. These bioactive ingredients contribute to mucosal hyperplasia.

Growth Factors Influence Growth and Differentiation of the Middle Ear Mucosa

OBJECTIVE

Otitis media is a major cause of morbidity in pediatric and adult patients. This inflammatory condition is characterized by mucosal hyperplasia that is thought to be mediated by the complex actions of growth factors and their respective receptors. It was the purpose of this study to determine which growth factors might be responsible for the growth and differentiation of the middle ear epithelium during otitis media.

STUDY DESIGN

The effect of several growth factors on the expansion and differentiation of normal middle ear mucosa was evaluated in tissue culture.

MATERIALS AND METHODS

Explants of normal rat middle ear mucosa were exposed in vitro to six different growth factors known to influence epithelial cells in other tissues: epidermal growth factor, amphiregulin, betacellulin, heregulin-alpha, keratinocyte growth factor, and hepatocyte growth factor.

RESULTS

After 12 days, the growth and level of cytokeratin expression were analyzed for each of the explant outgrowths. Each factor appeared to have a significant, concentration-dependent effect on either the growth or differentiation of the cultured middle ear epithelial cells.

CONCLUSION

The results suggest that several of the tested growth factors may play a significant role in controlling hyperplasia of the middle ear mucosa during otitis media.

Detection of mucin gene expression in normal rat middle ear mucosa by reverse transcriptase-polymerase chain reaction

Hypersecretion of mucin is a common feature of chronic and mucoid otitis media which may play an important role in hearing loss. The mechanisms controlling mucin secretion in the middle ear are not completely understood. Our reverse transcriptase-polymerase chain reaction results demonstrate that mRNAs of MUC1, MUC2, MUC3, MUC4 and MUC5AC are expressed in normal rat middle ear mucosa. Moreover, the expression of mRNA of the secretory mucins MUC2, MUC3 and MUC5AC was threefold lower in normal middle ear mucosa than that in the intestine or trachea. In contrast, expression of the membrane-bound mucins MUC1 and MUC4 was approximately the same in both middle ear mucosa and the intestine or trachea. MUC5AC proteins were also identified immunohistochemically in normal rat middle car epithelium. The methodology used in this study provides useful baseline information for investigation of the mechanisms of regulation of mucin gene expression during otitis media.

Kinetics of the ascension of NTHi from the nasopharynx to the middle ear coincident with adenovirus-induced compromise in the chinchilla

To determine the kinetics of ascension of the eustachian tube (ET) by non-typeable Haemophilus influenzae (NTHi) in situ from the nasopharynx to the middle ear using an experimental model of otitis media (OM), we examined snap-frozen sections of chinchilla ET and middle ear mucosa for adherent bacteria over a 14 day time period. Via fluorescent- and transmission electron-microscopy, we found that NTHi preferentially adhered not to the epithelial cells but to the mucus in the ET and gradually ascended this tubal organ, reaching the middle ear approximately 10 days after intranasal inoculation of adenovirus-infected animals. The number of NTHi adherent to mucus at the pharyngeal portion of the ET increased significantly in the first 4 days after inoculation of the nares whereas the number of adherent bacteria in both the mid and tympanic portions of the ET increased more gradually over time. NTHi were not observed in the middle ear until approximately 7-10 days after inoculation of the nares which was coincident with the onset of clinical signs of OM. These data confirmed our earlier in vitro investigation which suggested that adherence to and growth within stagnant mucus within a ET compromised by adenovirus was a possible mechanism by which NTHi, resident in the nasopharynx, might gain access to the middle ear and induce OM.

Round window membrane. Structure function and permeability: a review

The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 mu latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane.

Growth factors during endotoxin-induced otitis media

The presence of growth factors in the middle ear fluid was examined during lipopolysaccharide-induced otitis media (OM) in the chinchilla. There was a progressive significant increase in the proliferative activity detected in the LPS-free MEF by five days in culture. We conclude that lps indirectly mediates hyperproliferative changes in the middle ear during OM by inducing growth factors.

The relationship between middle ear pressure and deviated nasal septum

The deviated nasal septum may be associated with middle ear problems, particularly on the side of nasal obstruction. This study aims to find out whether middle ear pressure (MEP) correlates with the degree of nasal obstruction secondary to a deviated nasal septum, and to examine changes in MEP following septal surgery. Patencies of the nasal passages (measured with a peak nasal inspiratory flowmeter) and MEP (measured with a tympanometer) of 55 patients were obtained prior to surgery and 7.5 (6-10) months post-operatively [median (range)]. Forty patients completed the study. Results were analysed by linear regression. In the ear on the side of nasal blockage, MEP was -25.7 +/- 28.4 mm water pre-operatively, and following surgery increased significantly to -2.9 +/- 30.4 mm water (mean +/- SD) (P < 0.001). Pre-operatively, it was inversely related to the difference in patencies between the two nasal passages (r = -0.32, P < 0.02). Post-operatively, its improvement correlated with the degree of reduction of asymmetry of airway patency (r = 0.56, P < 0.001).

Cytological and histological changes in the middle ear after inoculation of influenza A virus

Experimental otitis media induced in the chinchilla by inoculation of influenza A virus into the middle ear resulted in capillary engorgement, subepithelial hemorrhage, tissue edema and acute inflammatory cell infiltration. Quantitative morphometric measurements were made for 28 days. Ciliated cells appeared to be the primary target of this strain of influenza virus and demonstrated the greatest degree of damage. Three weeks were required to restore the ciliated epithelium in the tubotympanum to normal levels.

Growth factors during proliferation of the middle ear mucosa

The presence of growth factors during otitis media with effusion (OME), induced by antigenic stimulation of the middle ear, was explored in guinea pigs. There was a significant increase in heparin-binding proliferative activity detected in mucosal tissue. This heparin-binding activity was identified as basic fibroblast growth factor (FGF) using several criteria. First, the majority of this activity was eluted from heparin-Sepharose gels with 1.3-1.8 M NaCl, consistent with basic FGF. Second, these fractions are potent stimulators of endothelial cell proliferation, characteristic of basic FGF. Third, the fractions contain basic FGF-like immunoreactivity based on radioimmunoassay. Finally, Western blotting of tissue extracts reveals the presence of an 18 kDa protein that is indistinguishable from basic FGF. We conclude that basic FGF plays a major role in the proliferation of the middle ear mucosa during OME.

Developmental anatomy of the eustachian tube and middle ear in mice

PURPOSE

It is generally accepted that the development of the tubotympanum has significant bearing on the susceptibility to ear infection. A detailed study of the differentiation of ciliated cells in secretory elements will be useful in understanding both the normal physiology and the pathology of the tubotympanum.

METHOD

Serially sectioned temporal bones of 76 mice ranging from gestational age day 11 to postnatal day 21 were examined microscopically.

RESULTS

During the period of gestation, the tubotympanic recess was formed at the 12th day and began to extend to form the middle ear between the 13th and 14th days. A rapid increase in the volume of the tubotympanic recess was observed between the 15th and 16th days when a definitive division of the tubotympanic recess into the eustachian tube and middle ear cavity was observed. Postnatally the tubotympanum attained an adult form around day 9, and the maximum change of middle ear volume was noted on day 11, when the mesenchymal tissue in the middle ear cavity disappeared completely. Development of the ciliated cells was observed concurrently in both the eustachian tube and middle ear on the 16th gestational day, one day earlier than the appearance of the epithelial secretory cells in both the eustachian tube and middle ear. The number of ciliated cells and secretory cells increased rapidly after birth. Tubal glands were well developed with evidence of secretory activity around the time of birth.

CONCLUSIONS

Based on these findings, one can conclude that the mucociliary defense system starts to develop during the fetal stage and is well established immediately after birth.

Ciliary activity in the tubotympanum during type I allergic reaction

The immune system is active in the tubotympanum and some middle ear diseases might be partially or exclusively immunologically mediated. However, the effect of an allergic reaction on the tubotympanic cilia remains to be elucidated. The response of normal tubotympanic cilia from the guinea pig was investigated in an in vitro experimental system to evaluate ciliary responsiveness without the influence of secretions. Mucosal samples were obtained from three different tubotympanic locations (Eustachian tube, and middle ear close to the tube (proximal site) and more distal to the tube (distal site)). Each mucosal sample was cultured in 2 ml of RPMI 1640 and 1 ml of heparinized venous blood from a nonallergic human subject, a patient with ragweed-sensitive nasal allergy, or 3 patients with Dermatophagoides farinae-sensitive nasal allergy. One microgram of D. farinae extracts was added in each chamber to evoke an in vitro allergic reaction, and the ciliary activity of the most active cell in each culture was monitored for up to 120 min. When D. farinae extracts were added into the chamber containing blood from subjects without sensitivity to D. farinae, no changes were induced in ciliary activity throughout the examination. When the same dose of allergens was added into the chamber containing blood from D. farinae-sensitive subjects, ciliary excitation was induced in the culture from the Eustachian tube and the proximal site. The peak and plateau of this phenomenon were observed at 30-40 min after the addition of the allergen, and a gradual slowdown to the baseline level was observed after the plateau. No ciliary depression was induced by an allergic reaction in the culture from the Eustachian tube or the proximal site. Such ciliostimulatory effects were correlated with D. farinae induced-percent histamine release from whole blood. In the cultures from the distal site, however, a gradual ciliodepression followed the peak of ciliary excitation. In conclusion, an in vitro allergic reaction affected the ciliary activity in the distal site, but such ciliary dysfunction was not observed in the Eustachian tube or the proximal site during such a reaction.

Macrophage (monocyte)-derived mucous secretagougue (MMS) is released into the fluid of the middle ear of patients with otitis media with effusion

Macrophage (monocyte)-derived secretagogue (MMS) is a low molecular weight peptide released by activated macrophages. This substance can enhance incorporation of carbohydrates into protein and result in the production of glycoproteins. It is believed that increased glycoproteins lead to the increased tenaciousness of mucoid effusions. Sixteen of 28 middle ear effusions demonstrated significant amounts of MMS. It is suggested that MMS is produced by activated macrophages in MEE and may lead to the development of glycoprotein by secretory epithelial cells. This substance may lead to the development of the mucoid effusion in otitis media with effusion in children.

Ultracytochemical demonstration of phospholipids in the surface layer of the guinea pig eustachian tube

The surface layer, especially the extracellular mucous blanket, in the eustachian tube of adult guinea pigs, was preserved very effectively with an intravascular perfusion of twice diluted Karnovsky's fixative following overnight incubation in the same fixative containing 1% tannic acid. Multilamellar bodies were observed in both mucous lining layers of the tube and the epithelial cells of its lining, but neither reticular nor lattice-like ultrastructures could be detected. Mucous blankets on the pharyngeal portion were composed of an electron-dense surface film and a hypophase. The hypophase was marked heterogenous, and it could hardly be observed on the isthmus. The enzymic digestive method using a purified phospholipase A2 was applied to the middle portion of the tube, and the reaction products, probably phospholipids, could be seen both on the surface film of the lining layers and around some of the dark inclusion bodies in the secretory cells. These findings suggest that such phospholipids may play an important role in reducing surface tension of the eustachian tube.

Experimental studies on round window structure: function and permeability

Current research and an overall review of 12 years of round window membrane studies is presented. The approach, rationale, and concepts that have evolved from the studies are described. An ultrastructural study of the round window membrane of rhesus monkeys disclosed three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Morphologic evidence in monkeys, cats, and chinchillas suggests that these layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Cationic ferritin, horseradish peroxidase, 1-micron latex spheres, and neomycin-gold spheres placed in the middle ear of these experimental animals were observed to traverse the round window membrane through pinocytotic vesicles. Three-micron latex spheres and anionic ferritin were not incorporated by the membrane. Cationic ferritin and 1-micron latex spheres placed in perilymph were incorporated by the inner epithelial cells, suggesting absorptive capabilities of the round window membrane. Cationic ferritin was observed within the mesothelial cells underlying the scala tympani side of the basilar membrane, suggesting a role for these cells in the inner-ear defense system. A review of the subject and a general perspective from the author's viewpoint are discussed.

Middle ear cilia activity as a determinant of tympanostomy tube placement

Three hundred and twenty-six patients with diagnoses of serous otitis media--or mucoid otitis media--were reviewed for the presence or absence of middle ear cilia activity. This study strongly suggests that if active cilia can be observed, ventilating tubes are not needed. This easily observed activity in the anterior-inferior quadrant offers the otolaryngologist an accurate tool for determination of the future health of the middle ear.

Histamine-induced middle ear effusion and mucosal histopathology in the guinea pig

It has been suggested that immune responses and resultant generation or release of inflammatory mediators play a role in otitis media with effusion (OME). To explore the potential of one such mediator to contribute to OME, the effects of histamine injected into the middle ear cavity were examined. Injection of histamine into the guinea pig middle ear was found to produce dilation and endothelial disjunction in capillaries, leading to striking mucosal edema and effusion which persisted for at least several hours. This response could be partially blocked by pretreatment with either H1 or H2 antihistamines. It is suggested that histamine released during immune responses in the middle ear may contribute to the formation of effusion and submucosal edema as observed in OME.

Acute otitis media. An animal experimental study

This paper describes an investigation performed to study the middle ear events ensuing from Staphylococcus aureus induced infection in the middle ear cavity of the rat. To obtain an evaluation at both the cell and the tissue level, scanning electron microscopy, transmission electron microscopy and histology were used. Staphylococcus aureus infection appears to be characterized by five major events: (i) cellular response, (ii) humoral response, (iii) mucociliary response, (iv) fibroblastic response, (v) bony response. Since these occurrences correspond to the events witnessed in the human middle ear affected by acute otitis media, S. aureus achieved infection might prove a useful tool for the further study of this disease, by means of animal experiments.

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.

The fine surface view of the human adult eustachian tube

The distribution pattern of ciliated cells and goblet cells in the mucosa of the normal adult human eustachian tube has been determined by means of SEM. In general, the density of the ciliated cells decreased from the pharyngeal to the tympanic orifice, and from the tubal floor to its roof. Most ciliated cells possessed about 100-200 cilia, and the average length of the cilia was approximately 8 mu. It is interesting to note that their number and length had a tendency to diminish towards the tympanic orifice of the tube. The ciliated epithelial cells at the tubal floor and lower parts of the walls undoubtedly play an important part in providing an active mucociliary mechanism, as in other parts of the upper respiratory system.

Sem studies of the inflammatory changes of the middle ear mucosa

Mucosal specimens of the middle ear from patients who had chronic otitis media were studied and compared with normal middle ear specimens using a scanning electron microscope. The epithelia in chronic otitis media were usually thick and those surface structures varied depending on the area in which the biopsy was taken. Moreover, the structure was not uniform even in the same specimen. Some areas showed a great number of secretory cells, while others demonstrated high population of ciliated cells. Areas with loss of the superficial layer were also observed in a few cases. There were less ciliated cells than we expected. They were not evenly distributed, except for the eustachian tube region. Morphologically, most of these ciliated cells seemed to be normal, and a few isolated atrophic ones were also observed. In cholesteatoma cases, squamous epithelia with desquamating, flat and keratinized cells were observed.

Localization of antileukoprotease in middle ear mucosa

The localization of antileukoprotease was studied immunohistologically in normal middle ear mucosa specimens obtained at autopsy and in chronically inflamed middle ear mucosa specimens obtained at middle ear surgery for chronic otitis media. In the sections of normal as well as in the sections of chronically inflamed middle ear mucosa, antileukoprotease localization was confined to PAS-positive goblet cells of surface epithelium and to PAS-positive goblet-like cells of submucosal glands and crypts, whereas ciliated mucosal cells and stratified squamous epithelial cells were devoid of anti-leukoprotease. In comparison with normal middle ear mucosa, an increased number of goblet cells--and thus an increased number of cells containing antileukoprotease--was present in the chronically inflamed middle ear mucosa. Since antileukoprotease is a potent inhibitor of granulocyte elastase and Cathepsin G, it was concluded that this proliferation of the respiratory epithelium during inflammatory processes in the middle ear indicates an increased activity of the biologic defence system against the action of granulocyte proteases.

Quantitative bacteriology in adenoid tissue

Over the past several years the indications for adenoidectomy have become increasingly controversial. Attempts to justify the operation in recurrent otitis media by correlating cultures of the nasopharynx with cultures of middle ear fluid have been inconclusive. Using quantitative bacteriologic techniques, we have studied the levels of aerobic and anaerobic bacteria per gram of tissue in adenoids removed from 48 patients. In seven patients, adenoidectomy was performed for nasal obstruction alone, in 17 patients for chronic serous otitis media, and in 24 patients for recurrent suppurative and serous otitis media. Using the criterion that greater than 10(5) organisms/gm of tissue constitutes infection, we found that 83% (20) of patients in the third group had infected adenoids, as opposed to only 15% (4) in the first and second group combined. Adenoid size measured radiographically did not correlate with the presence of infection. Adenoid size measured radiographically did not correlate with the presence of infection. When recurrent suppurative and serous otitis media are unresponsive to medical therapy including antibiotics and decongestants, adenoidectomy should be considered in addition to myringotomy and ventilation tubes.

Experimental otitis media following middle ear inoculation of nonviable Streptococcus pneumoniae

The pathogenesis of otitis media is poorly understood, and the events leading to bacterial invasion of the middle ear cleft and resulting inflammation are a matter of conjecture. While Streptococcus pneumoniae is the most frequent microbe cultured from acute, purulent middle ear effusions, it is infrequently cultured from nonsuppurative serous and mucoid effusion. To explore the possibility that nonviable pneumococci persisting in the middle ear cleft might produce mucosal inflammation, a solution of heat-killed pneumococci was placed in the middle ear cavity of experimental animals. Mucoperiosteal pathology which followed inoculation included an active, early subepithelial inflammatory response, metaplasia of the lining epithelium and later new bone formation. Thus, nonviable pneumococci are capable of producing middle ear inflammation, and it is possible that persistence of whole nonviable organisms or subcellular components in either middle ear effusion or mucoperiosteum may lead to continued middle ear inflammation or nonsuppurative otitis media.

Cells involved in the middle ear defense system

Despite the high incidence and prevalence of otitis media, its pathogenesis is not thoroughly understood. In the last decade, many efforts have been made to provide a better understanding, and abundant information has become available. At the same time the field of immunology has advanced at an extremely rapid pace. We have followed the gradual cellular events in the defense reaction of the middle ear, utilizing eustachian tube obstruction to induce otitis. Seventy-five cats were divided in groups and sacrificed at intervals between one day and six months, and their temporal bones were studied. During an initial phase of inflammation, polymorphonuclears appear at three days in connective tissue; at the same time active fibroblasts synthesize tropocollagen and ground substance while epithelial cells secrete mucus and lysozymes. These cells, together with those involved in the mucociliary transport system and a patent functional eustachian tube, constitute the nonspecific system of defense. The transition cells are the macrophages which appear at one week to interact with T and B cells to produce the specific immune response. Plasma cells appear at two weeks to peak at one month with synthesis of immunoglobulins A, G and M. A secretory immune system is observed. At three and six months, lymphocytes are the predominant cells and occasional accumulations of mononuclears are observed. The reaction involves the entire middle ear, including mucoperiosteum, middle ear muscles and round window membrane. We believe that a better understanding of the middle ear defense system will lead in time to a practical clinical assessment of the immunological status during the evolution of each particular process or disease involving the middle ear, and a more rational approach to the treatment and, hopefully, prevention of chronic ear disease.

The role of bacterial enzymes in inducing inflammation in the middle ear cavity

Current knowledge of the pathophysiology of bacterial infections is elementary. Thie initial events leading to the invasion of host tissues are a matter of conjecture for many bacterial organisms. This is particularly true for pneumococci, the most frequent causative organisms of acute otitis media. Bacterial enzymes may account for the initial disruption of host tissues, and this study explored their role in the infectious process. As first step, pneumococcal cultures were analyzed, and significant levels of the enzymes lipase and hyaluronidase were demonstrated. Secondly, the presence of these enzymes in middle ear effusions was explored in an animal model of acute otitis media. The enzymes reached peak levels at seven days. The third and most important portion of the study examined the significance of these enzymes in producing inflammation and alterations in the middle ear cavity of normal experimental animals. This portion was a histologic comparison of temporal bone specimens and demonstrated that marked acute and chronic changes can be induced by placing solutions of these enzymes in the middle ear cavity. This study concludes that bacterial enzymes play an important role in the induction of acute otitis media.

Otitis media with effusion: a steroid and antibiotic therapeutic trial before surgery

Eustachian tube dysfunction has been considered the main factor in the etiology of otitis media with effusion (OME). A short-term systemic steroid therapy, with combined chemotherapeutics, yielded 53.1% cure in 160 children in which OME had been diagnosed, whereas only 12.5% of similar 116 children were cured by chemotherapeutic treatment alone. It is postulated that steroids, acting by a mechanism much similar to the one in the newborn lung, increase the level of a tubal surface active agent, thus enhancing Eustachian tube refunctioning. This combined treatment, we believe, deserves its place as a routine conservative trial before surgery.

Middle ear mucosa in cleft palate children. A scanning electron microscopic study

Twenty-three promontory mucosal specimens from cleft palate children were studied by scanning electron microscope. Comparative studies were made, using light and transmission electron microscopy. The mucosal lining was pseudostratified columnar with microvilli, a few ciliated cells with secretory granules and numerous goblet cells. A few mucous glands, could be seen in certain areas. Microvilli with bulging tips and cilia with microknobs were common phenomena. The submucosa were inflamed, with leukocytes, macrophages, plasma cells and lymphocytes, indicating the presence of both cellular and humeral defence mechanisms.