Rabbit secretory IgA: identification and genetic control of two allotypes of secretory component.
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In order to identify expression of RNA transcripts for a number of important tracheobronchial cell products and molecules, we developed simple reverse transcription-polymerase chain reaction (RT-PCR) assays. Assays included the RNA for two apomucins (MUC1 and MUC2), secretory component, secretory leukocyte inhibitor protein, lysozyme, lactoferrin, 15-lipoxygenase, and the cystic fibrosis transmembrane conductance regulator. We tested RNA of normal and neoplastic origin. Sources of normal tissue included human tracheal surface epithelial cells and tracheobronchial submucosal tissues, acutely isolated human tracheal surface epithelial and tracheobronchial gland acini, and confluent cultures of human tracheal epithelial and tracheobronchial gland cells. Sources of neoplastic tissue included cell lines of non-small cell carcinomas of the lung. RNA expression was correlated with protein expression as assessed by immunocytochemistry. Tracheal surface epithelial tissues, isolated cells and cultures, and tracheobronchial submucosal tissues expressed RNA transcripts for all of the RNA transcripts assayed. Isolated gland acini and cultured gland cells expressed all RNA transcripts except 15-lipoxygenase. Expression of RNA transcripts by non-small cell lung carcinomas was heterogeneous and not necessarily influenced by histopathologic type. In most instances, RNA expression predicted expression of immunocytochemically detectable protein. These RT-PCR assays are useful for characterizing the molecular phenotype of cell cultures derived from normal or neoplastic airway epithelium and for establishing the potential of cultured cells for functional studies.
A new method is presented for the separation of secretory immunoglobulin A (SIgA) from salivary samples. Salivary proteins (from parotid or stimulated whole mouth saliva) were precipitated with methanol to concentrate SIgA from salivary samples whilst removing other salivary proteins. SIgA purified from breast milk and salivary proteins was separated by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions. Following completion of electrophoresis the top strip of gel was removed and the proteins present reduced with dithiothreitol. The gel strip was then applied to the top of a second 10% SDS gel, and the proteins were electrophoresed and then stained by Coomassie Brilliant Blue R-250. Three major protein bands were stained in all samples corresponding in molecular mass to secretory component, alpha-heavy chain and light chains of SIgA. Separated proteins were also electroblotted onto nitrocellulose and stained by fluorescein isothiocyanate (FITC). Lectin analysis was then used to detect the O-glycans present on IgA1. Lectins from Helix aspersa and Arachis hypogaea were used to determine the amount of terminal N-acetyl galactosamine and nonsialylated O-glycans, respectively. Maclura pomifera lectin was used to determine the total amount of IgA1 present on the blots. The results indicate that SlgA in stimulated whole mouth saliva, stimulated parotid saliva and purified from breast milk contain similar O-glycans.
Although bronchoalveolar lavage (BAL) has been used as a research tool for over a decade, the technique of lavage has varied markedly between laboratories. For example, lavage instillate volumes from 50 to 300 ml have been used, and yet the influence of the variable of total lavage volume on subsequent protein recovery is uncertain. We performed sequential BAL (50 ml/aliquot; total volume, 300 ml) of the right middle lobe of 14 normal volunteers and separately processed and analyzed recovered aliquots for the absolute and relative concentrations of several protein substances. These proteins include free secretory component and secretory IgA, which emanate from airway secretions, and IgG, which is thought to transude from more distal alveolar sites. Analysis of these data showed a marked decrease in the absolute concentration of all proteins measured in serial aliquots. Analysis of protein ratios in sequential aliquots, however, revealed no significant change from the first to the fifth recovered aliquot. Finally, we analyzed the influence of the size of the first recovered aliquot on absolute and relative concentrations of proteins. Here there seemed to be a trend indicating preferential recovery of airway proteins in smaller aliquots. This was significant for the ratio of free secretory component to albumin (p less than 0.05). We conclude that lung proteins are efficiently and homogeneously sampled with 100 ml of lavage instillate. Larger volumes will add more protein but not alter protein ratios. Lavage with smaller volumes may preferentially sample airway proteins.
An immunoperoxidase technique was applied to formalin and Helly fixed paraffin wax sections from cases of ulcerative colitis complicated by dysplasia and carcinoma for carcinoembryonic antigen and components of the colonic secretory immunoglobulin system--namely, secretory component, IgA, and J chain. Sections from both resection specimens and mucosal biopsies were available. Intensity of immunostaining was assessed qualitatively. There was appreciable variation in expression of carcinoembryonic antigen and secretory component antigens. Carcinoembryonic antigen stained heavily in dysplasia and carcinoma while these tissues showed only focal light staining for secretory component. Normal tissue stained heavily for secretory component. The variation in staining intensity for both carcinoembryonic antigen and secretory component in inflamed and regenerative mucosa precluded their use as a reliable diagnostic aid in discriminating these tissues from true dysplasia. Loss of secretory component production or transport or both may be incurred during malignant change, but it should not be assessed as an isolated index of epithelial maturity. The relation with mucosal plasma cells warrants further study to determine more fully the factors affecting tissue secretory component expression.