Distribution of immunocompetent cells in normal nasal mucosa: comparisons among germ-free, specific pathogen-free, and conventional mice

To better understand the role of immunocompetent cells in the defense mechanism of the upper respiratory tract against microbial invasions, the distribution patterns of those cells were investigated in nasal mucosa of mice maintained in three different conditions: germ-free (GF), specific pathogen-free (SPF), and conventional (CV) conditions. Immunostaining by the indirect peroxidase method and toluidine blue staining were employed for the detection of immunocompetent cells and mast cells. For immunostaining, anti-IgG, -IgA, and -IgM polyclonal antibodies and anti-Lyt-1, -Lyt-2, and -Mac-1 monoclonal antibodies were used as primary antibodies. In nasal mucosa of CV mice, Mac-1+ cells, mast cells, and all cell types of lymphocyte subsets were present. In nasal mucosa of SPF mice, all cell types were also positive, but fewer in number than those of CV mice. In nasal mucosa of GF mice, IgG+, IgA+, and Lyt-2+ cells were rare, although IgM+ and Lyt-1+ cells were present in small numbers. An electron microscopic study revealed that follicle-like lymphocyte aggregates with high endothelial venules were present in nasal mucosa close to the mucosal epithelia. These findings suggest that lymphocytes are mobilized to nasal mucosa, responding to continuous antigenic stimuli, and play an important role in the local defense mechanism of the upper respiratory tract.

Inhibition of bacterial adherence by nasopharyngeal secretions

The role of secretory immunoglobulin (Ig) A in nasopharyngeal secretions in the adherence of Streptococcus pneumoniae and Hemophilus influenzae to nasopharyngeal epithelial cells was investigated in vitro. The adherence was remarkably reduced by treating bacteria with nasopharyngeal secretions, and the antiadhesive activity was significantly greater in nasopharyngeal secretions having secretory IgA antibody activity against bacteria than in those having no activity. Noticeable changes were not observed in the antiadhesive activity caused by absorption of IgG from nasopharyngeal secretions. Results suggest that secretory IgA in nasopharyngeal secretions is related to bacterial adherence and adds to the prevention of nasopharyngeal infections.

Secretory IgA and serum type IgA in nasal secretion and antibody activity against the M protein

We studied IgA immunoglobulins in nasal secretions in order to clarify mucosal immunity of the nasal cavity and paranasal sinuses during chronic nasal infection. Secretory IgA and serum type IgA of 165 samples of nasal secretions were analyzed quantitatively by use of electroimmunodiffusion techniques, and the specific antibody activity of secretory IgA against the M protein of Streptococcus pyogenes was investigated by use of enzyme-linked immunosorbent assay. Results show that although the secretory IgA content in nasal secretions was elevated in chronic sinusitis, its specific antibody activity against the M protein was lower than that in normal subjects. This evidence suggests that nonspecific secretory IgA antibodies are predominantly produced in chronic sinusitis, and that mucosal immunity preventing the adherence of bacteria is impaired in the diseased mucosa.

Immunopathological study of the larynx. IgA distribution and secretory activity

Using immunofluorescent and histopathological techniques, we studied the distribution and secretory activity of the glands of the larynx from 55 humans. The cavity of the larynx was covered with secretory glandular cells with the exception of the true vocal cords, aryepiglottic folds and upper part of the laryngeal surface of the epiglottis. Immunofluorescent study revealed the presence of IgG and other immunoglobulins throughout the connective tissue ground in each laryngeal mucosa. The most striking was seen in the staining pattern of IgA. Diffuse fluorescence for IgA was observed not only in the submucosal or periglandular connective tissue area but also in the intraeptithelial or submucosa glands. Secretory component synthesis was found mainly in each serous-type glandular epithelium or acinus. In the submucosa or periglandular area, IgA producing plasma cells were numerous. Our observations suggest that IgA, produced locally, is secreted via the glandular cells as secretory component--SIgA. Secretory activity of SIgA in these glandular tissues indicates that the larynx is possibly an immunologically active organ in the upper respiratory tract.

Local immune system of nasal nucosa in inflammation. IgA distribution and secretory activity

The local immune system of human mucosa (inferior turbinates and nasal polyps) from 53 humans with chronic inflammation was studied by examining the distribution and secretory activity of IgA using an immunofluorescent technique. Diffuse fluorescence for IgA was observed throughout the connective tissue ground substance in every nasal turbinate and nasal polyp. In mucosa with mild inflammatory changes, most IgA seemed to be produced locally by IgA-producing plasma cells. However, in severely inflamed nasal mucosa, including nasal polyps, plasma cells were relatively fewer in number and the distribution of IgA generally corresponded to the pattern of fibrin deposition. Secretory activity of IgA in the glandular cells of nasal turbinates was well retained. Only in dilated glandular ductules in nasal polyps was the secretory activity impaired.

Loss of secretory activity in the glands of nasal polyps

Secretory activity in the glands of the nasal polyps from 15 patients with or without allergic histories was examined by using a direct (anti-IgA) or indirect (anti-SC) immunofluorescent technique. Glands were found in all the examined nasal polyps, but in many, only a few were present. Active secretory process of IgA was observed in the intraepithelial glands of the ciliated, pseudostratified epithelium. Most of the dilated glandular ductules, on the contrary, appeared to be lacking in secretory activity of IgA. Such were commonly filled with mucus materials and their epithelial glandular cells showed no fluorescence for anti-SC, whereas the active IgA secreting cells showed a heavy fluorescence for secretory component (SC) in indirect immunofluorescent studies. Activity of the glandular ductules, therefore, was determined by examining the SC producing activity. In some extracted polyps, SC containing dilated glands were present. These active glands, however, lost the SC producing activity followed by the stasis of mucus flow in the lumen. Thus, when the glands were occupied by mucus materials, stretched and cystic degeneration ensued.

Pneumococcal antibodies in maxillary sinus secretion

Resistance to and recovery from mucosal surface infections may be better correlated to the presence of local antibodies than to serum antibodies. In 14 patients with maxillary sinusitis due to pneumococci, IgA, IgG and IgM antibodies to the isolated pneumococci were quantified in sinus secretion and serum by indirect immunofluorescence technique. Most secretions contained type specific pneumococcal antibodies, mainly of IgA class. The frequent lack of demonstrable type specific IgA antibodies in serum indicates their local synthesis. After drainage of purulent sinus secretion, as in 5 patients, a local increase of antibodies was observed.