Distribution of human PLUNC/BPI fold-containing (BPIF) proteins

Although gene expression studies have shown that human PLUNC (palate, lung and nasal epithelium clone) proteins are predominantly expressed in the upper airways, nose and mouth, and proteomic studies have indicated they are secreted into airway and nasal lining fluids and saliva, there is currently little information concerning the localization of human PLUNC proteins. Our studies have focused on the localization of three members of this protein family, namely SPLUNC1 (short PLUNC1), SPLUNC2 and LPLUNC1 (long PLUNC1). Western blotting has indicated that PLUNC proteins are highly glycosylated, whereas immunohistochemical analysis demonstrated distinct patterns of expression. For example, SPLUNC2 is expressed in serous cells of the major salivary glands and in minor mucosal glands, whereas SPLUNC1 is expressed in the mucous cells of these glands. LPLUNC1 is a product of a population of goblet cells in the airway epithelium and nasal passages and expressed in airway submucosal glands and minor glands of the oral and nasal cavities. SPLUNC1 is also found in the epithelium of the upper airways and nasal passages and in airway submucosal glands, but is not co-expressed with LPLUNC1. We suggest that this differential expression may be reflected in the function of individual PLUNC proteins.     

Tissue distribution of the secretory protein, SPLUNC1, in the human fetus

We previously identified a tissue-specific gene, short palate, lung, and nasal epithelium clone 1 (SPLUNC1), in nasopharyngeal epithelial tissues. SPLUNC1 was differentially expressed in nasopharyngeal carcinoma. Bioinformatic analysis revealed that SPLUNC1 has the bactericidal permeability-increasing protein/lipid-binding protein (BPI/LBP) domain and a 19 amino acid signal peptide, which suggest that it is a secretory protein. Its precise cellular localization in the respiratory tract is mainly in mucous cells and ducts of submucosal glands. However, little is known about its expression pattern in various human tissues. We generated a highly specific antibody and analyzed its distribution in the human fetus by immunohistochemistry to more precisely determine SPLUNC1 protein localization in human tissues. The results were further validated by RT-PCR. Our results showed that SPLUNC1 protein is expressed at not only the serous glands and epithelium of the upper respiratory tract and digestive tract, but also in the oculi of human embryos. Interestingly, we also found positive staining in fetus adipose tissue, a result not previously reported in studies of adult human tissues. Western blot analysis detected a 24 kDa SPLUNC1 protein in the compounds of nasopharyngeal secretions. This secretory protein was also detected in saliva and tears. Our research suggests that SPLUNC1 protein may not only be an antimicrobial peptide that plays an important role in the maintenance of homeostasis in the upper respiratory tract, oculi, and alimentary tract, it may also be important in the development and lipid metabolism of the adipose tissue.     

Differential localisation of BPIFA1 (SPLUNC1) and BPIFB1 (LPLUNC1) in the nasal and oral cavities of mice

Despite being initially identified in mice, little is known about the sites of production of members of the BPI fold (BPIF) containing (PLUNC) family of putative innate defence proteins in this species. These proteins have largely been considered to be specificaly expressed in the respiratory tract, and we have recently shown that they exhibit differential expression in the epithelium of the proximal airways. In this study, we have used species-specific antibodies to systematically localize two members of this protein family; BPIFA1 (PLUNC/SPLUNC1) and BPIFB1 (LPLUNC1) in adult mice. In general, these proteins exhibit distinct and only partially overlapping localization. BPIFA1 is highly expressed in the respiratory epithelium and Bowman??s glands of the nasal passages, whereas BPIFB1 is present in small subset of goblet cells in the nasal passage and pharynx. BPIFB1 is also present in the serous glands in the proximal tongue where is co-localised with the salivary gland specific family member, BPIFA2E (parotid secretory protein) and also in glands of the soft palate. Both proteins exhibit limited expression outside of these regions. These results are consistent with the localization of the proteins seen in man. Knowledge of the complex expression patterns of BPIF proteins in these regions will allow the use of tractable mouse models of disease to dissect their function.     

Aquaporins in complex tissues. II. Subcellular distribution in respiratory and glandular tissues of rat

The molecular pathways for fluid transport in pulmonary, oral,and nasal tissues are still unresolved. Here we use immunocytochemistry and immunoelectron microscopy to define the sites of expression of fouraquaporins in the respiratory tract and glandular epithelia, where theyreside in distinct, nonoverlapping sites. Aquaporin-1 (AQP1) is presentin apical and basolateral membranes of bronchial, tracheal, andnasopharyngeal vascular endothelium and fibroblasts. AQP5 is localizedto the apical plasma membrane of type I pneumocytes and the apicalplasma membranes of secretory epithelium in upper airway and salivaryglands. In contrast, AQP3 is present in basal cells of tracheal andnasopharyngeal epithelium and is abundant in basolateral membranes ofsurface epithelial cells of nasal conchus. AQP4 resides in basolateralmembranes of columnar cells of bronchial, tracheal, and nasopharyngealepithelium; in nasal conchus AQP4 is restricted to basolateralmembranes of a subset of intra- and subepithelial glands. These sitesof expression suggest that transalveolar water movement, modulation ofairway surface liquid, air humidification, and generation ofnasopharyngeal secretions involve a coordinated network of aquaporinwater channels.

     

Characterisation and expression of SPLUNC2, the human orthologue of rodent parotid secretory protein

We recently described the Palate Lung Nasal Clone (PLUNC) family of proteins as an extended group of proteins expressed in the upper airways, nose and mouth. Little is known about these proteins, but they are secreted into the airway and nasal lining fluids and saliva where, due to their structural similarity with lipopolysaccharide-binding protein and bactericidal/permeability-increasing protein, they may play a role in the innate immune defence. We now describe the generation and characterisation of novel affinity-purified antibodies to SPLUNC2, and use them to determine the expression of this, the major salivary gland PLUNC. Western blotting showed that the antibodies identified a number of distinct protein bands in saliva, whilst immunohistochemical analysis demonstrated protein expression in serous cells of the major salivary glands and in the ductal lumens as well as in cells of minor mucosal glands. Antibodies directed against distinct epitopes of the protein yielded different staining patterns in both minor and major salivary glands. Using RT-PCR of tissues from the oral cavity, coupled with EST analysis, we showed that the gene undergoes alternative splicing using two 5′ non-coding exons, suggesting that the gene is regulated by alternative promoters. Comprehensive RACE analysis using salivary gland RNA as template failed to identify any additional exons. Analysis of saliva showed that SPLUNC2 is subject to N-glycosylation. Thus, our study shows that multiple SPLUNC2 isoforms are found in the oral cavity and suggest that these proteins may be differentially regulated in distinct tissues where they may function in the innate immune response.     

Trachea,lung, and tracheobronchial lymph nodes are the major sites where antigen-presenting cells are detected after nasal vaccination of mice with human papillomavirus type 16 virus-like particles

Vaccination by the nasal route has been successfully used for the induction of immune responses. Either the nasal-associated lymphoid tissue (NALT), the bronchus-associated lymphoid tissue, or lung dendritic cells have been mainly involved. Following nasal vaccination of mice with human papillomavirus type 16 (HPV16) virus-like-particles (VLPs), we have previously shown that interaction of the antigen with the lower respiratory tract was necessary to induce high titers of neutralizing antibodies in genital secretions. However, following a parenteral priming, nasal vaccination with HPV16 VLPs did not require interaction with the lung to induce a mucosal immune response. To evaluate the contribution of the upper and lower respiratory tissues and associated lymph nodes (LN) in the induction of humoral responses against HPV16 VLPs after nasal vaccination, we localized the immune inductive sites and identified the antigen-presenting cells involved using a specific CD4(+) T-cell hybridoma. Our results show that the trachea, the lung, and the tracheobronchial LN were the major sites responsible for the induction of the immune response against HPV16 VLP, while the NALT only played a minor role. Altogether, our data suggest that vaccination strategies aiming to induce efficient immune responses against HPV16 VLP in the female genital tract should target the lower respiratory tract.     

Interleukin-1 beta and tumor necrosis factor-alpha induce MUC5AC overexpression through a mechanism involving ERK/p38 mitogen-activated protein kinases-MSK1-CREB activation in human airway epithelial cells

Mucin hypersecretion is commonly observed in many inflammatory diseases of the respiratory tract. MUC5AC is generally recognized to be a major airway mucin because MUC5AC is highly expressed in the goblet cells of human airway epithelium. Moreover, it is regulated by various inflammatory cytokines. However, the mechanisms by which the interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha induce MUC5AC gene expression in normal nasal epithelial cells, and the signal molecules involved, especially in the downstream signaling of mitogen-activated protein (MAP) kinases, remain unclear. Here we show that pharmacologic or genetic inhibition of either ERK or p38 MAP kinase pathway abolished IL-1beta- and TNF-alpha-induced MUC5AC gene expression in normal human nasal epithelial cells. Our results also indicate that the activation of mitogen- and stress-activated protein kinase 1 (MSK1) and cAMP-response element-binding protein and cAMP-response element signaling cascades via ERK and p38 MAP kinases are crucial aspects of the intracellular mechanisms that mediate MUC5AC gene expression. Taken together, these studies give additional insights into the molecular mechanism of IL-1beta- and TNF-alpha-induced MUC5AC gene expression and enhance our understanding on mucin hypersecretion during inflammation.     

Combined oral/nasal immunization protects mice from Sendai virus infection

Based on the concept of a common mucosal immune system wherein mucosal associated lymphocytes traffic among the various mucous membranes, the murine gastrointestinal tract was immunized with Sendai virus antigens in order to elicit a virus-specific immune response in the respiratory tract. Multiple intragastric (oral) administration of live or killed Sendai virus induced IgA and IgG antiviral antibodies in both gastrointestinal secretions and serum. When cholera toxin as an adjuvant was included along with virus, gut IgA and IgG as well as serum IgA responses were enhanced. Antiviral antibodies induced in respiratory secretions by oral killed virus plus cholera toxin, however, were variable and protection from virus challenge was not demonstrated. Significantly higher levels of respiratory antiviral antibodies were induced if immunization with oral killed Sendai virus/cholera toxin was combined with intranasal administration of small amounts of killed virus. The combined immunization also resulted in protection of both the upper and lower respiratory tracts from virus infection. Protection of the upper respiratory tract was correlated with the presence of IgA antiviral antibodies in nasal washings. On the other hand, protection of the lower respiratory tract was correlated with IgG antiviral antibodies in bronchoalveolar lavage fluids. Immunization with intranasal killed virus alone conferred partial protection to the lower respiratory tract and no protection to the upper respiratory tract. Thus, oral immunization with killed virus antigen could prime for a protective immune response in the murine respiratory tract and this protective response included IgA antibodies.     

Expression of taste receptors in Solitary Chemosensory Cells of rodent airways

Background

Chemical irritation of airway mucosa elicits a variety of reflex responses such as coughing, apnea, and laryngeal closure. Inhaled irritants can activate either chemosensitive free nerve endings, laryngeal taste buds or solitary chemosensory cells (SCCs). The SCC population lies in the nasal respiratory epithelium, vomeronasal organ, and larynx, as well as deeper in the airway. The objective of this study is to map the distribution of SCCs within the airways and to determine the elements of the chemosensory transduction cascade expressed in these SCCs.

Methods

We utilized a combination of immunohistochemistry and molecular techniques (rtPCR and in situ hybridization) on rats and transgenic mice where the Tas1R3 or TRPM5 promoter drives expression of green fluorescent protein (GFP).

Results

Epithelial SCCs specialized for chemoreception are distributed throughout much of the respiratory tree of rodents. These cells express elements of the taste transduction cascade, including Tas1R and Tas2R receptor molecules, α-gustducin, PLCβ2 and TrpM5. The Tas2R bitter taste receptors are present throughout the entire respiratory tract. In contrast, the Tas1R sweet/umami taste receptors are expressed by numerous SCCs in the nasal cavity, but decrease in prevalence in the trachea, and are absent in the lower airways.

Conclusions

Elements of the taste transduction cascade including taste receptors are expressed by SCCs distributed throughout the airways. In the nasal cavity, SCCs, expressing Tas1R and Tas2R taste receptors, mediate detection of irritants and foreign substances which trigger trigeminally-mediated protective airway reflexes. Lower in the respiratory tract, similar chemosensory cells are not related to the trigeminal nerve but may still trigger local epithelial responses to irritants. In total, SCCs should be considered chemoreceptor cells that help in preventing damage to the respiratory tract caused by inhaled irritants and pathogens.     

Enhanced susceptibility of nasal polyp tissues to avian and human influenza viruses

Background

Influenza viruses bind and infect respiratory epithelial cells through sialic acid on cell surface. Differential preference to sialic acid types contributes to host- and tissue-tropism of avian and seasonal influenza viruses. Although the highly pathogenic avian influenza virus H5N1 can infect and cause severe diseases in humans, it is not efficient in infecting human upper respiratory tract. This is because of the scarcity of its receptor, α2,3-linked sialic acid, in human upper airway. Expression of sialic acid can be influenced by various factors including inflammatory process. Allergic rhinitis and nasal polyp are common inflammatory conditions of nasal mucosa and may affect expression of the sialic acid and susceptibility to influenza infection.

Methodology/Principal Finding

To test this hypothesis, we detected α2,3- and α2,6-linked sialic acid in human nasal polyp and normal nasal mucosal tissues by lectin staining and infected explants of those tissues with avian influenza viruses H5N1 and seasonal influenza viruses. We show here that mucosal surface of nasal polyp expressed higher level of α2,3- and α2,6-linked sialic acid than normal nasal mucosa. Accordingly, both H5N1 avian influenza viruses and seasonal influenza viruses replicated more efficiently in nasal polyp tissues explants.

Conclusions/Significance

Our data suggest a role of nasal inflammatory conditions in susceptibility to influenza infection, especially by avian influenza viruses, which is generally inefficient in infecting human upper airway. The increased receptor expression may contribute to increased susceptibility in some individuals. This may contribute to the gradual adaptation of the virus to human population.     

The expression of the eotaxins IL-6 and CXCL8 in human epithelial cells from various levels of the respiratory tract

Airway epithelium acts as multifunctional site of response in the respiratory tract. Epithelial activity plays an important part in the pathophysiology of obstructive lung disease. In this study, we compare normal human epithelial cells from various levels of the respiratory tract in terms of their reactivity to pro-allergic and pro-inflammatory stimulation. Normal human nasal, bronchial and small airway epithelial cells were stimulated with IL-4 and IL-13. The expressions of the eotaxins IL-6 and CXCL8 were evaluated at the mRNA and protein levels. The effects of pre-treatment with IFN-γ on the cell reactivity were measured, and the responses to TNF-α, LPS and IFN-γ were evaluated. All of the studied primary cells expressed CCL26, IL-6 and IL-8 after IL-4 or IL-13 stimulation. IFN-γ pre-treatment resulted in decreased CCL26 and increased IL-6 expression in the nasal and small airway cells, but this effect was not observed in the bronchial cells. IL-6 and CXCL8 were produced in varying degrees by all of the epithelial primary cells in cultures stimulated with TNF-α, LPS or IFN-γ. We showed that epithelial cells from the various levels of the respiratory tract act in a united way, responding in a similar manner to stimulation with IL-4 and IL-13, showing similar reactivity to TNF-α and LPS, and giving an almost unified response to IFN-γ pre-stimulation.     

Morphology of the nasal fossae and associated structures of the hamster (Mesocricetus auratus)

The hamster nasal cavity consists of vestibular, non-olfactory and olfactory portions. Much of the non-olfactory nasal cavity surface is lined by cuboidal, stratified cuboidal, and low columnar epithelia, devoid of cilia. Goblet cells and ciliated respiratory epithelium are present over only a small portion of the nasal cavity surface. The largest glandular masses in the hamster nose are the maxillary recess glands, the vomeronasal glands and the lateral nasal gland 1; these three glands contain neutral mucopolysaccharides (PAS-positive). Other nasal glands contain both acidic and neutral mucopolysaccharides; the staining reaction for acidic mucopolysaccharide is stronger in goblet cells and olfactory glands than in the other nasal glands. The ducts which open into the nasal vestibule are the excretory ducts of compound tubuloacinar serous glands. The one major PAS-positive gland whose duct opens into the nasal vestibule is the lateral nasal gland 1. The ducts of the compound tubuloacinar vomeronasal glands open into the lumen of the vomeronasal organ, which is connected to the ventral nasal meatus by means of the vomeronasal duct. The ducts of the branched tubuloacinar maxillary recess glands open into the maxillary recess. Few ducts open into the caudal half of the nasal cavity.     

Functional roles of SPLUNC1 in the innate immune response against Gram-negative bacteria

PLUNC (palate, lung and nasal epithelium clone)-associated gene originally referred to one gene, but now has been extended to represent a gene family that consists of a number of genes with peptide sequence homologies and predicted structural similarities. PLUNC-like proteins display sequence homology with BPI (bactericidal/permeability-increasing protein), a 456-residue cationic protein produced by precursors of polymorphonuclear leucocytes that have been shown to possess both bactericidal and LPS (lipopolysaccharide)-binding activities. The human PLUNC is also known as LUNX (lung-specific X protein), NASG (nasopharyngeal carcinoma-related protein) and SPURT (secretory protein in upper respiratory tract). The gene originally named PLUNC is now recognized as SPLUNC1. Its gene product SPLUNC1 is a secretory protein that is abundantly expressed in cells of the surface epithelium in the upper respiratory tracts and secretory glands in lung, and in the head and the neck region. The functional role of SPLUNC1 in innate immunity has been suggested but not clearly defined. The present review describes recent findings that support antimicrobial and anti-inflammatory functions of SPLUNC1 in Gram-negative bacteria-induced respiratory infection.     

Distribution of T-cell subsets and immunoglobulin-containing cells in nasal-associated lymphoid tissue (NALT) of chickens

The present study demonstrated the localization of the T-cell subsets (CD4+ and CD8+) and immunoglobulin (Ig)-containing cells (IgA, IgM, and IgG) in the nasal mucosa and its accessory structures. These lymphoid structures may be compared with nasal-associated lymphoid tissue (NALT) of rats and mice. In the chicken NALT, T-cell subsets were more widely distributed than Ig-containing cells, especially in large lymphoid accumulations restricted to the respiratory mucosa in the nasal cavity and the nasolacrimal duct. These lymphoid accumulations in the mucosa of the nasal cavity and nasolacrimal duct consisted of widely distributed CD8+ cells and deeply aggregated CD4+ cells adjacent to large germinal centers. In these lymphoid accumulations, IgG-containing cells were more frequently observed than IgM- and IgA-containing cells. T-cell subsets, predominantly CD8+ cells were more widely distributed in the duct epithelium of the lateral nasal glands than Ig-containing cells. Moreover, numerous CD8+ cells and a few Ig-containing cells were found in the chicken salivary glands, especially around the orifice of their ducts into the oral cavity. Therefore, it seems likely that the chicken NALT plays an important part in the upper respiratory tract, with a close relationship to the paraocular immune system.     

MUC16 is produced in tracheal surface epithelium and submucosal glands and is present in secretions from normal human airway and cultured bronchial epithelial cells

The gel-forming MUC5AC and MUC5B mucins have been identified as major components of human airway mucus but it is not known whether additional mucin species, possibly with other functions, are also present. MUC16 mucin is a well-known serum marker for ovarian cancer, but the molecule has also been found on the ocular surface and in cervical secretions suggesting that it may play a role on the normal mucosal surface. In this investigation, the LUM16-2 antiserum (raised against a sequence in the N-terminal repeat domain) recognized MUC16 in goblet and submucosal gland mucous cells as well as on the epithelial surface of human tracheal tissue suggesting that the mucin originates from secretory cells. MUC16 mucin was present in 'normal' respiratory tract mucus as well as in secretions from normal human bronchial epithelial (NHBE) cells. MUC16 from NHBE cells was a high-molecular-mass, monomeric mucin which gave rise to large glycopeptides after proteolysis. N- and C-terminal fragments of the molecule were separated on gel electrophoresis showing that the MUC16 apoprotein undergoes a cleavage between these domains, possibly in the SEA domain as demonstrated for other transmembrane mucins; MUC1 and MUC3. After metabolic labeling of NHBE cells, most of the secreted monomeric, high-molecular-mass [(35)S]sulphate-labelled molecules were immunoprecipitated with the OC125 antibody indicating that MUC16 is the major [(35)S]sulphate-labelled mucin in NHBE cell secretions.     

Nonolfactory surface epithelium of the nasal cavity of the bonnet monkey: a morphologic and morphometric study of the transitional and respiratory epithelium

The purpose of the present study was to characterize ultrastructurally the nonolfactory nasal epithelium of a nonhuman primate, the bonnet monkey. Nasal cavities from eight subadult bonnet monkeys were processed for light microscopy, and scanning and transmission electron microscopy. Nonolfactory epithelium covered the majority of the nasal cavity and consisted of squamous (SE), transitional (TE), and respiratory epithelium (RE). Stratified SE covered septal and lateral walls of the nasal vestibule, while ciliated pseudostratified RE covered most of the remaining nasal cavity. Stratified, nonciliated TE was present between SE and RE in the anterior nasal cavity. This epithelium was distinct from the other epithelial populations in abundance and types of cells present. TE was composed of lumenal nonciliated cuboidal cells, goblet cells, small mucous granule (SMG) cells, and basal cells, while RE contained ciliated cells, goblet cells, SMG cells, basal cells, and cells with intracytoplasmic lumina lined by cilia and microvilli. TE and RE contained similar numbers of total epithelial cells and basal cells per millimeter of basal lamina. TE was composed of more SMG cells but fewer goblet cells compared to RE. We conclude that nonolfactory nasal epithelium in the bonnet monkey is complex with distinct regional epithelial populations which must be recognized before pathologic changes within this tissue can be assessed adequately.     

Oral administration of cholera toxin-Sendai virus conjugate potentiates gut and respiratory immunity against Sendai virus

Successful oral immunization to prevent infectious diseases in the gastrointestinal tract as well as distant mucosal tissues may depend on the effectiveness of an Ag to induce gut immune responses. We and others have previously reported that cholera toxin possesses strong adjuvant effects on the gut immune response to co-administered Ag. To explore further adjuvant effects of cholera toxin, the holotoxin or its B subunit was chemically cross-linked to Sendai virus. The resulting conjugates, which were not infectious, were evaluated for their capacity to induce gut immune responses against Sendai virus after oral administration to mice. Conjugating cholera toxin to virus significantly enhanced the adjuvant activity of cholera toxin compared to simple mixing. Cholera toxin B subunit, however, did not show an adjuvant effect either by itself or conjugated with the virus. Oral administration of the Sendai virus-cholera toxin conjugate was also able to prime for protective anti-viral responses in the respiratory tract. Mice that were orally immunized with the conjugate and intra-nasally boosted with inactivated virus alone showed virus-specific IgA titers in nasal secretions that correlated with protection against direct nasal challenge with live Sendai virus. For comparison, s.c. immunization was also studied. Systemic immunization with the virus-cholera toxin conjugate induced virus-specific antibody responses in serum as well as in the respiratory tract but failed to protect the upper respiratory tract against virus challenge. Systemic immunization plus an intra-nasal boost did, however, confer a variable degree of protection to the upper respiratory tract, which correlated primarily with bronchoalveolar lavage (lung) antibody titers.     

Biosynthesis of respiratory-tract mucins. A comparison of canine epithelial goblet-cell and submucosal-gland secretions

1. A modified canine tracheal organ culture system was used to investigate differences between mucous secretions of epithelial goblet cells and the submucosal glands. 2. Denuded explants were prepared by removing goblet, ciliated and basal cells from the surface epithelium leaving an intact basement membrane and viable submucosa. 3. Denuded explants actively incorporated radioactive precursors into secreted macromolecules when cultured in medium 199 containing label. 4. Chromatography on Bio-Gel A-150m and electrophoresis on 1% agarose gels indicated that epithelial goblet cell secretions were relatively more sulphated than submucosal glandular secretions. 5. The glandular structures were shown to respond to a parasympathomimetic agent.     

Expression and localization of surfactant proteins in human nasal epithelium

Surfactant proteins (SPs), designated SP-A, SP-B, SP-C, and SP-D, play an important role in surfactant metabolism and host defense mechanisms in the lung. This study investigates expression of the different SP types in human nasal mucosa and cultured normal human nasal epithelial (NHNE) cells and whether the expression of SP mRNA is influenced by the degree of mucociliary differentiation. RT-PCR was performed with mRNA from cultured NHNE cells and nasal mucosa. Immunohistochemical staining for SPs was performed on nasal mucosa specimens. Western blot analysis was performed on cell lysates from cultured NHNE cells. SP-A2, SP-B, and SP-D mRNAs were expressed in normal NHNE cells and human nasal mucosa. SPs were localized in ciliated cells of the surface epithelium and serous acini of the submucosal glands. SP-A, SP-B, and SP-D proteins were expressed in cultured NHNE cells. The degree of mucociliary differentiation influenced expression of the SP gene. We demonstrate that SP-A, SP-B, and SP-D are expressed in human nasal mucosa and cultured NHNE cells. Further study of the functional role of SPs in the upper airway is required.