The human secretory immunoglobulin system: immunohistoligical localization of gamma A, secretory "piece," and lactoferrin in normal human tissues

Detection of infiltrating fibroblasts by single-cell transcriptomics in human kidney allografts

We tested the hypothesis that single-cell RNA-sequencing (scRNA-seq) analysis of human kidney allograft biopsies will reveal distinct cell types and states and yield insights to decipher the complex heterogeneity of alloimmune injury. We selected 3 biopsies of kidney cortex from 3 individuals for scRNA-seq and processed them fresh using an identical protocol on the 10x Chromium platform; (i) HK: native kidney biopsy from a living donor, (ii) AK1: allograft kidney with transplant glomerulopathy, tubulointerstitial fibrosis, and worsening graft function, and (iii) AK2: allograft kidney after successful treatment of active antibody-mediated rejection. We did not study T-cell-mediated rejections. We generated 7217 high-quality single cell transcriptomes. Taking advantage of the recipient-donor sex mismatches revealed by X and Y chromosome autosomal gene expression, we determined that in AK1 with fibrosis, 42 months after transplantation, more than half of the kidney allograft fibroblasts were recipient-derived and therefore likely migratory and graft infiltrative, whereas in AK2 without fibrosis, 84 months after transplantation, most fibroblasts were donor-organ-derived. Furthermore, AK1 was enriched for tubular progenitor cells overexpressing profibrotic extracellular matrix genes. AK2, eight months after successful treatment of rejection, contained plasmablast cells with high expression of immunoglobulins, endothelial cell elaboration of T cell chemoattractant cytokines, and persistent presence of cytotoxic T cells. In addition to these key findings, our analysis revealed unique cell types and states in the kidney. Altogether, single-cell transcriptomics yielded novel mechanistic insights, which could pave the way for individualizing the care of transplant recipients.

Know your enemy or find your friend?-Induction of IgA at mucosal surfaces

Most antibodies produced in the body are of the IgA class. The dominant cell population producing them are plasma cells within the lamina propria of the gastrointestinal tract, but many IgA-producing cells are also found in the airways, within mammary tissues, the urogenital tract and inside the bone marrow. Most IgA antibodies are transported into the lumen by epithelial cells as part of the mucosal secretions, but they are also present in serum and other body fluids. A large part of the commensal microbiota in the gut is covered with IgA antibodies, and it has been demonstrated that this plays a role in maintaining a healthy balance between the host and the bacteria. However, IgA antibodies also play important roles in neutralizing pathogens in the gastrointestinal tract and the upper airways. The distinction between the two roles of IgA - protective and balance-maintaining - not only has implications on function but also on how the production is regulated. Here, we discuss these issues with a special focus on gut and airways.

COVID-19 during Pregnancy and Postpartum

As the COVID-19 pandemic intensified the global health crisis, the containment of SARS-CoV-2 infection in pregnancies, and the inherent risk of vertical transmission of virus from mother-to-fetus (or neonate) poses a major concern. Most COVID-19-Pregnancy patients showed mild to moderate COVID-19 pneumonia with no pregnancy loss and no congenital transmission of the virus; however, an increase in hypoxia-induced preterm deliveries was apparent. Also, the breastmilk of several mothers with COVID-19 tested negative for the virus. Taken together, the natural barrier function during pregnancy and postpartum seems to deter the SARS-CoV-2 transmission from mother-to-child. This clinical observation warrants to explore the maternal-fetal interface and identify the innate defense factors for prevention and control of COVID-19-Pregnancy. Lactoferrin (LF) is a potent antiviral iron-binding protein present in the maternal-fetal interface. In concert with immune co-factors, maternal-LF modulates chemokine release and lymphocyte migration and amplify host defense during pregnancy. LF levels during pregnancy may resolve hypertension via down-regulation of ACE2; consequently, may limit the membrane receptor access to SARS-CoV-2 for cellular entry. Furthermore, an LF-derived peptide (LRPVAA) has been shown to block ACE receptor activity in vitro. LF may also reduce viral docking and entry into host cells and limit the early phase of COVID-19 infection. An in-depth understanding of LF and other soluble mammalian milk-derived innate antiviral factors may provide insights to reduce co-morbidities and vertical transmission of SARS-CoV-2 infection and may lead to the development of effective nutraceutical supplements.

Localization and Regulation of Polymeric Ig Receptor in Healthy and Diseased Human Kidney

The polymeric Ig receptor (PIgR) constitutes an important part of the immune system by mediating transcytosis of dimeric IgA into mucosal fluids. Although well studied in organs such as the intestine, the regulation and localization of PIgR in human kidney are incompletely characterized. Herein, using immunohistochemistry, we show that in healthy human kidneys, PIgR is expressed by the progenitor-like tubular scattered cells of the proximal tubules and by parietal epithelial cells of glomeruli. We further show that proximal tubular expression of PIgR becomes widespread during kidney disease, correlating to elevated levels of urinary secretory IgA. Urinary secretory IgA levels also correlated to the degree of tubular fibrosis, plasma creatinine, and urea levels. In addition, primary tubular cells were cultured to study the function and regulation of PIgR in vitro. Cellular PIgR expression was induced by conditioned medium from activated human leukocytes, as well as by inflammatory cytokines, whereas transforming growth factor-β1 caused decreased expression. Furthermore, interferon-γ increased the transcytosis of dimeric IgA in cultured tubular cells. Finally, a correlation study of mRNA data from the Genotype-Tissue Expression portal indicated that PIGR mRNA expression in kidney correlates to the expression of TNFSF13, a cytokine involved in plasma cell class switching to IgA. These results indicate that PIgR induction is an integral part of the injury phenotype of renal tubular cells.

Secretory Immunoglobulin a in Oral and Respiratory Passages in Man

Secretory IgA (SIgA) is the predominant immunoglobulin in certain external secretions and may have an important role in immunological mucosal resistance. SIgA differs in chemical and immunological properties from serum IgA. The present study was undertaken to investigate the antigenic relationship between SIgA, free secretory component (FSC) and serum IgA and the localization of SIgA as well as other immunological classes in tissues of oral and respiratory passages by use of immunofluorescence technique. SIgA and FSC were highly purified from human colostrum and rabbit anti-SIgA and anti-SC antisera were prepared. On the basis of antigenic relationships between SIgA, FSC and serum IgA, it was emphasized that individual specific antisera for SC and IgA and/or SIgA should be used in immunochemical or immunohistological investigations for SIgA. The present study failed to detect SC determinants in palatine and lingual tonsils. However, it was evident that cells present in the pharyngeal tonsillar epithelium contain SC determinants. SC molecules may be synthesized in certain secretory cells of mucous membrane and glandular epithelium and the combining of SC with IgA could occur in the cytoplasm of epithelial cells, the intercellular spaces and/or in the lumens of glandular acini and ductules.

Down-regulation of the polymeric immunoglobulin receptor in non-small cell lung carcinoma: correlation with dysregulated expression of the transcription factors USF and AP2

The polymeric immunoglobulin receptor (PIGR) mediates transport of IgA and IgM antibodies across mucosal and glandular epithelia. Several studies have utilized immunohistochemistry to demonstrate that PIGR expression varies in different types of lung carcinoma, and is down-regulated during tumor progression. We have previously shown in cultured tumor cell-lines that basal transcription of the PIGR gene is regulated by the transcription factors USF1, USF2 and AP2. To examine the mechanism by which PIGR expression is down-regulated in lung carcinoma, RNA was microdissected from formalin-fixed, paraffin-embedded lung carcinomas (14 adenocarcinomas and 8 squamous cell carcinomas). Levels of PIGR, USF1, USF2 and AP2-alpha mRNA were quantified by real-time reverse transcriptase-polymerase chain reaction and normalized to mRNA for the housekeeping gene GAPDH. PIGR mRNA levels were decreased in adenocarcinomas and squamous cell carcinomas relative to adjacent non-tumor tissue, and were inversely correlated with stage of differentiation. USF1 and USF2 mRNA levels were reduced in adenocarcinomas relative to non-tumor tissue, while AP2-alpha levels were elevated. Multivariate regression analysis demonstrated that reduced USF2 mRNA and increased AP2-alpha mRNA levels were predictive of down-regulated PIGR mRNA expression in the majority of adenocarcinomas and in moderately differentiated squamous cell carcinomas.

The role of eye-associated lymphoid tissue in corneal immune protection

Because the cornea is optimized for refraction, it relies on supporting tissues for moistening and nutrition and in particular for immune protection. Its main support tissue is the conjunctiva, in addition to the lacrimal gland, the latter which provides soluble mediators via the tear film. The cornea and conjunctiva constitute a moist mucosal surface and there is increasing evidence that apart from innate defence mechanisms, also lymphoid cells contribute to the normal homeostasis of the corneal surface. A Medline-based literature search was performed in order to review the existing literature on the existence, composition and functions of mucosa-associated lymphoid tissue (MALT) at the ocular surface for corneal protection. The existence of lymphoid cells at the ocular surface and appendage has been known for many years, but for a long time they were believed erroneously to be inflammatory cells. More recent research has shown that in addition to the known presence of lymphoid cells in the lacrimal gland, they also form MALT in the conjunctiva as conjunctiva-associated lymphoid tissue (CALT) and in the lacrimal drainage system as lacrimal drainage-associated lymphoid tissue (LDALT). Together this constitutes an eye-associated lymphoid tissue (EALT), which is a new component of the mucosal immune system of the body. When the topographical distribution of CALT is projected onto the ocular surface, it overlies the cornea during eye closure and is hence in a suitable position to assist the corneal immune protection during blinking and overnight. It can detect corneal antigens and prime respective effector cells, or distribute protective factors as secretory IgA.

Active synthesis of mouse polymeric immunoglobulin receptor in the epithelial cells of the distal urinary tubule in kidney

The tissue distribution of mouse polymeric immunoglobulin receptor (pIgR) has been demonstrated. By Northern blot hybridization, pIgR mRNA expression was detected in liver, intestine, stomach, lung and kidney. A weak expression was also detected in thymus by reverse transcriptase-polymerase chain reaction. The pIgR expression in kidney was further studied and confirmed that pIgR protein was actively synthesized in the epithelial cells of distal urinary tubule and of Henle's loop. Immunoelectron microscopical analysis showed the accumulation of pIgR-containing vesicles in the apical portion of distal urinary tubule epithelial cells.

Single chain Fv: a ligand in receptor-mediated gene delivery

We have used an anti-human polymeric immunoglobulin receptor (pIgR) single chain Fv (scFv) to deliver reporter genes to epithelial cells in vitro. The scFv was constructed from a monoclonal antibody directed against pIgR and a cysteine residue was added at the carboxyl end to facilitate its conjugation to polylysine (polyK) via the heterobifunctional cross-linker SPDP. ScFv-cys was expressed in Drosophila S2 cells and purified to homogeneity using conventional column chromatography. ScFv-polyK, and polyK as control, were condensed with a DNA expression plasmid containing the luciferase reporter gene driven by the CMV promoter into unimolecular (with respect to DNA) complexes under high salt conditions. Target cells were MDCK cells transfected with human pIgR and repeatedly sorted for high-level receptor expression, with untransfected MDCK cells as control. Receptor-bearing MDCK cells were readily transfected by scFv-cys containing, pIgR directed complexes, and expression could be blocked by addition of excess human secretory component (SC), the extracellular portion of pIgR. In contrast, MDCK cells that did not express pIgR were not transfected. Nontargeted complexes were not effective in transfecting MDCK cells with or without pIgR. Targeted complexes also transfected human tracheal epithelial cells in primary culture, corroborating the pIgR-mediated gene delivery. These data indicate that a scFv directed against human pIgR can direct foreign genes specifically into receptor-bearing cells in vitro. We have expressed and purified a ligand that is efficient and specific in pIgR-mediated gene delivery.

Immunohistochemical study of ceruloplasmin, lactoferrin and secretory component expression in neoplastic and non-neoplastic thyroid gland diseases

The expression of lactoferrin (LF), ceruloplasmin (CP) and secretory component (SC) in various thyroid diseases was investigated using an immunohistochemical method. LF is an iron-binding protein overexpressed in certain human adenocarcinomas. CP is implicated in carcinogenesis and SC is part of the local immune defense system. Sections of 15 follicular adenomas, 5 follicular carcinomas (FC), 16 papillary carcinomas (PC), 15 goitres and 2 cases of lymphocytic thyroiditis were re-examined and investigated immunohistologically by a streptavidin-biotin method. A positive immunostain reaction for CP and LF was observed in all cases of PC and FC. A positive immunostain reaction for SC was observed in 13/16 cases of PC and 4/5 cases of FC. A negative immunostain reaction for CP, LF and SC was observed in medullary cancers, in follicular adenomas and in the cases with goitre. We conclude that the immunostain expression of LF, CP and SC is a valuable diagnostic aid in the differential diagnosis between benign and malignant thyroid tumors. The expression of SC indicates the presence of a local immunodefensive system.

Expression of lactoferrin in the kidney: implications for innate immunity and iron metabolism

BACKGROUND

Sequestering of free iron by lactoferrin (LF) is important in the defense against bacteria. In a screening for LF expression in various organs, high levels of LF mRNA were detected in human kidney. This indicated that LF is produced by the kidney and that it may participate in innate immunity of this organ.

METHODS AND RESULTS

Antibody staining and in situ hybridization of paraffin-embedded kidney sections showed that LF is expressed in cells lining the distal collecting ducts of the medulla. High levels of both protein and mRNA were detected in these cells. However, a clear difference in the distribution of mRNA and protein within the tissue was observed. LF mRNA was detected along a relatively large portion of the tubuli, whereas LF antigen was found mainly in the very distal regions of the same tubuli. This indicates that LF is released by large regions of the tubuli and possibly reabsorbed in the most distal parts. Using enzyme-linked immunosorbent assay, only very low LF levels were detected in urine.

CONCLUSION

The present study shows that LF is produced by the kidney and that both LF mRNA and protein are distributed in a highly ordered fashion. This latter finding, together with the very low levels of LF detected in urine, indicates that LF may contribute to the immune defense in the kidney by reduction of available free iron in the urine. Other possibilities are that LF may play a role in the iron metabolism by recovering free iron from urine and making it available for metabolic use, and that LF may participate in the antioxidant defense systems protecting the kidney against nonmicrobial oxidative injury, that is, ischemia, reperfusion and inflammation.

In vitro transport of active alpha(1)-antitrypsin to the apical surface of epithelia by targeting the polymeric immunoglobulin receptor

In cystic fibrosis (CF), the intense host inflammatory response to chronic infection largely accounts for the progressive pulmonary disease, and ultimately death. Neutrophils are the prominent inflammatory cells in the lungs of patients with CF, and large amounts of neutrophil elastase (NE) are released during phagocytosis. Besides having direct effects on structural elastin, NE stimulates the release of proinflammatory mediators from the respiratory epithelium and is a potent secretogogue. Therapeutic use of elastase inhibitors in CF has been complicated by difficulties in delivery to the critical site in the airway-the surface of the epithelium. We describe a unique strategy to protect the respiratory epithelial cell surface directly by capitalizing on the nondegradative transcytotic pathway of the polymeric immunoglobulin receptor (pIgR). A recombinant fusion protein was constructed consisting of an antihuman pIgR single-chain Fv (scFv) antibody linked to human alpha(1)-antitrypsin (A1AT), an inhibitor of NE. The recombinant scFv-A1AT fusion protein bound specifically to the pIgR on the basolateral surface of an epithelial cell monolayer, and was transported and released into the apical medium where the A1AT domain was capable of forming an inactivation complex with NE. Thus, A1AT linked to an antihuman pIgR scFv was delivered in receptor-specific fashion from the basolateral to apical surface and was released as an active antiprotease, indicating that it is feasible to deliver therapeutic proteins to the apical surface of epithelia by targeting the pIgR.

Synthesis of secretory component by rat hepatocytes in culture

Normal rat hepatocytes were isolated and cultivated in vitro. Synthesis of secretory component was demonstrated by its accumulation in the culture medium, as measured by radioimmunoassay; by incorporation of 14C-leucine in the protein specifically precipitated with anti-secretory component antiserum; and by a positive precipitin reaction of concentrated culture medium with the same antiserum. The results explain the high levels of secretory component found in rat bile and render plausible a mechanism of hepatic IgA transfer involving secretory component as the hepatocyte membrane receptor for polymeric IgA.

Secretory immunoglobulin A in pancreatic juice and pancreatic tissue of patients with chronic pancreatitis

BACKGROUND

The predominance of secretory IgA (S-IgA) in intestinal secretions compared with blood is well established, but concentrations of this protein in pancreatic juice and its origin, especially in chronic pancreatitis, are unknown.

AIMS

To investigate the role of S-IgA in chronic pancreatitis.

PATIENTS

Twenty one patients with chronic pancreatitis (group I), three patients with proven malignancies (group II), and 12 patients without pancreatic disease (group III).

METHODS

Pure human pancreatic juice was collected endoscopically in four fractions after consecutive stimulation with secretin and cholecystokinin (CCK). Samples were analysed for S-IgA, protein, trypsinogen, and proteolytic activity.

RESULTS

The S-IgA level was significant increased in fraction 1 of pancreatic juice of group I (1210 (1411) ng/ml) compared with controls (33 (70) ng/ml). Protein concentrations and trypsinogen content were lower in group I than in the other groups. Proteolytic activity could be observed in 53% of all 133 pancreatic juice samples, but in 87% of fraction 1. In pancreatic tissue of three patients with chronic pancreatitis both IgA and secretory component were detected by immunohistology. Expression of the secretory component by human pancreatic epithelial cells was increased in patients with chronic pancreatitis compared with normal controls. The concentration of S-IgA in pancreatic juice did not correlate with the serum S-IgA level. In contrast, serum levels of S-IgA were decreased in patients with chronic pancreatitis.

CONCLUSION

There are high levels of S-IgA in human pancreatic juice following chronic inflammation and a protective role is suggested for this immunoglobulin.

Biosynthesis and secretion of MHC class III gene products (complement C4 and factor B) in the exocrine pancreas

We recently found that complement C3 is locally synthesized and secreted into the exocrine pancreas. In the present study, we attempted to demonstrate the secretion of complement C4 and factor B in the exocrine pancreas. In five samples of pancreatic fluid, both C4 and factor B proteins were detected by enzyme-linked immunosorbent assay (ELISA). Immunoblot analysis revealed the C4 and factor B molecules in pancreatic fluid to be identical with these molecules in serum. Reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis in pancreatic carcinoma cell lines suggested ductal epithelial cells to be the local production sites of these proteins in the pancreas. The secretion of C4 and factor B in ductal cell lines (PANC-1 and MIA PaCa-2) was independently regulated by interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma; C4 secretion was induced by IFN-gamma, whereas factor B secretion was induced by IL-1 beta, TNF-alpha, or IFN-gamma. These observations indicate that: (a) complement C4 and factor B are secreted into the exocrine pancreas, (b) ductal epithelial cells appear to be the site of C4 and factor B biosynthesis, and (c) local secretion of C4 and factor B in the pancreas is differentially regulated by IL-1 beta, TNF-alpha, and IFN-gamma.

Urinary secretory immunoglobulin A and free secretory component in pyelonephritis

The immune defense mechanisms of mucosal surfaces involve secretory immunoglobulin A (sIgA) antibodies and, to a lesser degree, other specific and nonspecific immune factors. These antibodies are dependent on a secretory component (SC) for their transmission through the epithelium. This SC is also secreted without Ig as free SC (FSC). The kidney does produce these proteins; however, the ability of the lower urinary tract to secrete them has not been shown. Thus, an upper urinary tract infection should produce more urinary sIg and possibly more FSC than a lower tract infection. To demonstrate this, urine was obtained from normal controls (N = 33), cystitis patients (N = 22), and pyelonephritis patients (N = 27). Monoclonal antibodies binding to specific conformational epitopes were used in an enzyme-linked immunosorbent assay to detect the levels of sIgA and FSC in these groups. Previous sIgA measurements have been hampered by lack of specificity of the capture antibody. Urine creatinine was obtained to correct for the effect of diuresis. A one-tailed Student's t-test for nonparametric populations was performed to assess differences. The sIgA levels in the normal and cystitis groups were equivalent (1.4 micrograms/mg/mL and 1.3 micrograms/mg/mL, respectively; P = 0.32). When these two groups were compared with the pyelonephritis group (24.1 micrograms/mg/mL), a statistically significant difference was seen (P = 0.012 and P = 0.011, respectively), with no overlap. There was a statistical difference in the levels of FSC in these same groups, but a large degree of overlap.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression and purification of biologically active domain I of the human polymeric immunoglobulin receptor

Previous studies using proteolytic fragments and synthetic peptides have indicated that domain I of human polymeric immunoglobulin receptor (PIgR) is necessary for ligand binding. The expression in E. coli, and subsequent IgM-affinity purification of domain I of human PIgR is described. The recombinant domain I protein (rDI) was similar in structure to native SC domain I in that it bound specifically to MAb 6G11, an antibody which recognizes a critical portion of the PIg binding site in domain I. The biological activity of rDI was indicated by high affinity binding to PIgA (Kd = 1.6 x 10(-7) M) and IgM (Kd = 5.1 x 10(-7) M). Domain I of human SC is therefore sufficient for binding to PIg.

Development of secretory elements in murine tubotympanum: lysozyme and lactoferrin immunohistochemistry

Secretory activity, particularly of antibacterial agents such as lysozyme and lactoferrin, is an important aspect of the mucosal defense mechanism, and the development of these agents may have a direct bearing on the susceptibility of the ear to infection. In this study, the secretory cells of the murine tubal epithelium were first observed at gestational day 17. Although tubal glands began to develop on gestational day 18, their secretory activity was first shown on postnatal day 3. The number of secretory cells of the tubal epithelium increased rapidly immediately after birth, while that of the tubal glands showed a gradual increase from postnatal day 3. The epithelial secretory cells in the tubotympanum matured at birth, but the tubal glands matured gradually after birth. Lysozyme was first recognized in the epithelial secretory cells on postnatal day 1, while lactoferrin was first detected in the tubal glands on postnatal day 3. Both lysozyme and lactoferrin were co-localized in the serous cells of the tubal glands. The secretion of lysozyme and lactoferrin seemed to reflect the maturation of the secretory cells in the murine tubotympanum.

Secretion of alpha-amylase in human parotid gland epithelial cell culture

The secretions of the salivary gland system are essential for the maintenance of oral health. The nature of cell-specific secretions of the various glands and their regulation is not completely understood. The objective of this study was to establish epithelial cell cultures from the human parotid gland that exhibit the tissue-specific function of alpha-amylase secretion. A specimen of normal human parotid gland was obtained at surgery and used to obtain primary cultures by the explant/outgrowth procedure. The cultures were maintained in keratinocyte basal medium, supplemented with insulin (5 micrograms/ml), EGF (10 ng/ml), hydrocortisone (0.5 micrograms/ml), bovine pituitary extract (25 micrograms/ml), and antibiotics. The cultures were passaged using 0.125% trypsin to dissociate the cells. Phase contrast and ultrastructural observations showed that the cells were polygonal and exhibited desmosomes. Their cytoplasm contained tonofilament bundles and abundant rough endoplasmic reticulum and Golgi complexes. Immunofluorescence studies showed that all cells were positive for cytokeratins. Immunoblot analysis revealed keratins with molecular weights of 58, 56, 52, 50, 48, 46, and 40 KD, which are characteristic of secretory epithelia. The cells have been passaged 35 times so far, undergoing a cumulative 120-140 population doublings. The serially passaged epithelial cell cultures produced and secreted alpha-amylase, a major component of parotid gland acinar cell secretion. The beta-adrenergic agonist, isoproterenol (ISP), stimulated alpha-amylase secretion, which was accompanied by increased intracellular concentrations of cAMP. ISP-induced stimulation of amylase and cAMP was blocked by the beta-adrenergic antagonist, propranolol. Further, dibutyryl cAMP also enhanced the secretion of amylase. Thus we have established a long-term epithelial cell culture model of human parotid gland epithelial cells that exhibits differentiated function and retains the intact beta-adrenergic receptor system.

The usefulness of routine screening for salivary secretory component

Secretory IgA is a dimeric immunoglobulin found in association with the J chain and secretory component (SC). It is secreted into saliva and other mucosal fluids and is involved in mucosal immunity. The absence of either SC or secretory IgA may be associated with recurrent sinopulmonary infections, diarrhea, and failure to thrive. We present a retrospective study of 1262 samples from 877 patients who were screened for salivary IgA, SC, and serum immunoglobulin levels. Forty-six patients (5.2%) of those tested were found to have absent salivary SC. Although only 19 of these patients (41.3%) could be retested, all were found to have SC on repeated testing. Of the patients whose initial samples of saliva exhibited no SC, 15% (6/46) had low or absent serum IGA (less than 10 mg/dl) in contrast to 8.6% (66/769) of patients whose saliva contained detectable SC, but this was not statistically significant (chi 2 = 1.93; p greater than 0.1). There was also no correlation between serum immunoglobulin levels and the absence of SC. Because of the rarity of salivary SC deficiency, routine screening is not valuable.

Epithelial polymeric immunoglobulin receptors

The secretory immune system, which leads to secretion of polymeric immunoglobulins along mucosal surfaces, has not been shown to have any definite role in cutaneous immunology, although the polymeric immunoglobulin receptor, secretory component (SC), has been found in sweat glands and possibly in the epidermis. The purpose of this study is to examine normal human skin and cultured human keratinocytes for the presence of SC. Positive staining for SC was found in sections of normal human skin along the basement membrane zone with use of a polyclonal antibody to SC and focally on the surfaces of epidermal cells with use of a monoclonal antibody to SC. Granular cell-surface fluorescence of an intensity far less than that of the positive control HT 29 cells was seen when cultured human keratinocytes were stained for SC by indirect immunofluorescence (IF). Study of lysates of both HT 29 cells and HK by immunoblotting have been negative, perhaps due to destruction of the protein or loss of antigenicity during the extraction process. If human keratinocytes are capable of expression of SC, and the receptor can interact with IgA and IgM, this might be a mechanism for protection of the skin from microbial agent or foreign antigens and might be relevant to the deposition of IgA seen in certain skin diseases.

Immunoglobulins in Hassall's corpuscles of the human thymus

Ninety nine human thymuses were examined immunohistochemically for the presence of immunoglobulins G, A, M. D and E, light-chains, secretory component and albumin in the cells of Hassall's corpuscles. Igs G, A, M and secretory component were present. These showed a rise after birth until the age of 20 years and also increased with the degree of involution, falling when involution became complete. Albumin was also consistently demonstrated. There was a degree of correlation between the presence of Igs and production of Igs G, A and M by plasma cells in the thymic medulla. There was a close correlation between the amounts of IgA and secretory component in the cells of Hassall's corpuscles and the thymus may have to be regarded as a part of the secretory-IgA system. Light chains of the immunoglobulin molecule were also present, with lambda predominating over kappa, possibly reflecting the same kappa/lambda ratio found with thymic immunoglobulin production. No IgD or IgE was demonstrated. The presence of albumin may represent a passive uptake of protein in senescent cells but a more active uptake of Igs, particularly IgG and IgA, could be postulated. The production of Igs in the thymus and their presence in Hassall's corpuscles could be of significance in the maturation and regulation of the immune response.

The measuring of "respiratory-membrane permeability" and local production of immunoglobulins and antibodies by means of an analysis of sputum

When measuring the exudation of serum proteins and the local production of immunoglobulins and antibodies within the lung by means of an analysis of sputum, the permeability properties of the respiratory membrane should be taken into account. In this paper, we describe the "loss of size selectivity" that usually accompanies an increased permeability on the part of the respiratory membrane. This phenomenon enables us to measure respiratory membrane permeability independently of the sputum water content. Consequences with regard to discrimination between leakage from the circulation and/or local production of immunoglobulins and antibodies are discussed. Sequential studies which take these factors into account may provide insights into the extent of local inflammatory reactions in individual patients.

Secretory immunoglobulin A in urinary tract infection, chronic glomerulonephritis, and renal transplantation

An enzyme-linked immunoassay (ELISA) for the quantitation of secretory IgA (S-IgA) in the urine is described. The assay is sensitive (linear down to 0.02 microgram/ml), specific, and reproducible (intraassay variation 7.8%, interassay variation 18.9%). The assay was used to determine the urinary excretion rates of S-IgA in patients with bladder catheter (n = 12), cystotomy and urinary tract infection (n = 13), urosepsis (n = 5), chronic glomerulonephritis, including IgA-nephritis (n = 31), in renal allograft recipients (n = 30), and in healthy controls (n = 46). An elevated S-IgA urinary excretion (P less than 0.01) was found in all patient groups studied. The highest values were observed in urosepsis. No significant differences between S-IgA levels in IgA-nephritis and other forms of chronic glomerulonephritis were detected. The elevated S-IgA excretion in renal allograft recipients indicates that immunosuppressive therapy does not influence the local S-IgA production in the urinary tract. The susceptibility of these patients to urinary tract infections is therefore not due to a S-IgA deficiency.

Secretory immunoglobulin A in sweat gland tumors

The presence of immunoglobulin A (IgA) and secretory component (SC) was investigated in normal human skin and in cutaneous neoplasms including a variety of sweat gland tumors. Immunohistochemistry in normal sweat glands revealed the occurrence of secretory IgA (sIgA) as indicated by reactivity for IgA and SC in serial sections. The majority of 28 cases of sweat gland tumors could be demonstrated to retain their ability to produce IgA and SC. In normal as well as in neoplastic sweat glands heaviest staining for sIgA could be found in the lumina and at the surface of lining epithelia. This is comparable with the presence of sIgA in breast or intestinal neoplasms. In contrast other epidermal cysts or solid tumors were not labelled. In view of recent immunohistochemical studies the demonstration of IgA and SC may be of differentiating value in cutaneous glandular neoplasms.

Immunohistochemical demonstration of lysozyme and lactoferrin in salivary pleomorphic adenomas

Immunohistochemical identification of lysozyme and lactoferrin was made in salivary pleomorphic adenomas (147 cases) and the staining patterns were evaluated with respect to the histological features and histogenesis. In normal salivary glands, the intercalated duct cells gave positive staining for lysozyme in major glands, and serous acinar cells, demilune cells, and interlobular duct cells were positive in minor glands. Lactoferrin staining was irregularly positive in serous cells and ductal epithelium. In pleomorphic adenomas, the reaction for lysozyme was positive in 14% (21/147) of the cases, and was confined to luminal cells of tubulo-ductal structures. Lactoferrin in pleomorphic adenomas was distributed in luminal tumor cells (51%; 75/147), in outer tumor cells (3%; 4/147), and in both luminal and outer tumor cells (5%; 7/147) in tubulo-ductal structures; it was also detected in plasmacytoid myoepithelial cells (5%, 8/147). However, modified myoepithelial cells and other types of neoplastic myoepithelial participants were negative for lactoferrin staining. The occurrence of both lysozyme and lactoferrin in salivary pleomorphic adenomas suggests their participation in the local defense mechanism in the tumor.

Immunohistochemical demonstration of immunoglobulin A in human sebaceous and sweat glands

Immunoglobulin A (IgA) mediated humoral defense mechanisms have been detected on all mucous membrane surfaces. There are only a few papers about the presence of IgA in human skin. In order to demonstrate the occurrence of IgA in sebaceous and sweat glands, biopsies of normal human skin were investigated and compared to intestinal mucosa. Two different commercially available anti-IgA antibodies were used. For light microscopy peroxidase-anti-peroxidase (PAP) or avidin-biotin complex (ABC) staining was used, and for electron microscopy protein-A-gold (PAG) labeling was performed on tissue sections. Specifically decorated IgA was found in sebaceous glands as well as in various portions of eccrine glands. In sebaceous glands, the maximum of IgA concentration was seen near the mouth of pilosebaceous ducts. Sweat ducts exhibited a continuous coat of IgA, whereas secretory portions contained only singular scattered IgA positive cells. Immunoelectron microscopy suggests endocytotic uptake and processing of IgA in the glandular cells. These results indicate strongly that IgA are secreted by normal human sebaceous and sweat glands. Because it is well known that IgA plays an important role in inactivation of invading viruses, bacteria, and other antigenic structures on mucous membranes, it appears that IgA in sebum and sweat fulfil a similar function on the outer body surface.

Absence of secretory component expression by epithelial cells overlying rabbit gut-associated lymphoid tissue

The expression of secretory component by epithelial cells overlying intestinal lymphoid aggregates was examined immunocytochemically in rabbits. Intensely labeled epithelial cells were distributed along surfaces of villi surrounding follicles in jejunal and ileal Peyer's patches and along interdomal epithelium in sacculus rotundus and appendix. Secretory component labeling extended from within crypts and appendiceal crevices to the tips of villi and interdomal regions. In contrast, no immunologically detectable secretory component sites were observed in follicle-associated epithelial cells. In crypts and crevices supplying follicles, epithelial cells facing the lamina propria of villi and interdomal epithelium expressed secretory component, but cells flanking the follicle domes lacked secretory component immunostaining, with a clear demarcation between positive and negative zones at the base of the stem cell regions. These findings demonstrate a unique difference in the expression of the receptor for immunoglobulin A antibody between follicle-associated and non-follicle-associated epithelium.

Immunoelectron microscopical localization of immunoglobulins, secretory component and J chain in the human minor salivary glands

Localization of IgA, secretory component (SC) and J chain was investigated immunocytochemically in minor salivary glands of the lip and palate to define the mechanism involved in the transport of immunoglobulin A (sIgA) into the saliva from the minor salivary glands. SC synthesis was detected in mucous acinar cells and ductal epithelial cells. Free SC is secreted into the saliva through secretory granules in the mucous acinar cells. Dimeric IgA containing J chain is translocated through these cells as sIgA by a SC-mediated transport mechanism involving cytoplasmic vesicles.

Expression of IgA and secretory component in the normal and in adenocarcinomas of Fallopian tube, endometrium and endocervix

The occurrence and localization of IgA and secretory components (SC) were examined in the normal and in adenocarcinomas of Fallopian tube, endometrium and endocervix. IgA-containing immunocytes were identified in the stroma of 90% of normal Fallopian tubes. It is suggested that the Fallopian tube may have an immunological function and may, together with the endocervix, constitute the local secretory immune system of the female genital tract. IgA and SC were frequently demonstrated in the cytoplasm and luminal secretion of adenocarcinomas of the endocervix, endometrium and Fallopian tube. This study has shown a decrease in immunoreactivity of SC among poorly differentiated adenocarcinomas but has failed to demonstrate any correlation between the expression of IgA and the degree of differentiation of the tumours. Secretory component appears, therefore, to be more useful than IgA as an indicator of secretory activity and differentiation of adenocarcinomas of the female genital tract.

Identification of secretory immunoglobulin A in human sweat and sweat glands

Secretory immunoglobulin A (sIgA) plays an important role in local immune defense mechanisms. Although skin is always exposed to external antigens, the role of local immune defenses involving sIgA in the skin has not been adequately studied. In order to evaluate the presence of sIgA in sweat, we have measured the concentration of sIgA in human sweat by enzyme immunoassay and have localized the components of sIgA in the sweat glands of human axillary skin. The concentration of sIgA in sweat was found to be 10 times higher in men than in women (13.0 +/- 0.9 micrograms/ml versus 1.6 +/- 0.9 micrograms/ml). Secretory component (SC) was localized immunohistochemically in protein synthetic organelles, such as the perinuclear spaces and Golgi complex, in cytoplasmic vesicles, and along the external surface membranes of mucous cells on the terminal segment of eccrine sweat glands. IgA and J chain were present in plasma cells in the protein synthetic organelles. The luminal aspects of eccrine sweat ducts also strongly express SC, as well as IgA and J chain. Neither SC, IgA, or J chain were identified in epithelial cells of apocrine sweat glands. These findings are consistent with the theory that J chain complexed with dimeric IgA is synthesized in plasma cells and is transported by SC-mediated endocytosis transfer across mucous cells of eccrine sweat glands and thus into sweat.

Acute and chronic bacterial infection in the rat urinary tract: immunofluorescent localization of immunoglobulins

To study the relative concentrations and appearance of immunoglobulin in the bladder and kidneys of rats with acute and chronic urinary tract infections, three groups of female Sprague-Dawley rats were studied. Group I underwent weekly intraurethral inoculation with Escherichia coli 07. Group II received inoculation of 0.2 ml of PBS alone. Group III were unmanipulated controls. Bladder and kidney washings were obtained for bacterial colony counts and organism identification. Bladder and kidney tissue was prepared for immunofluorescent examination using goat or rabbit antirat IgA, IgM, or IgG layered with fluorescent-labeled rabbit antigoat or goat antirabbit serum. Negative immunofluorescent controls substituted PBS for antirat serum. No significant difference was noted between bladder and kidney cultures in groups I and II. Comparison of immunofluorescent intensity between groups I and III demonstrated that IgM intensity was greatest between weeks one and three in bladders and kidneys, then decreased to non-significant levels. Bladder IgG intensity peaked at week four and remained elevated throughout the remainder of the study while renal IgG intensity was significant throughout the study period. Renal and bladder IgA was noted only sporadically. Comparison of culture positive animals to culture negative animals (groups II and III) demonstrated a lower immunofluorescent intensity score for culture negative animals. Discrete cellular immunofluorescence was evident in 19.1% of bladders and compared to 0.6% of kidneys. This study suggests that the immunologic response in the rat to intraurethral inoculation and infection is biphasic (IgM followed by IgG) and that a local cellular immunologic response may exist in the bladder.

Serum and skin surface antibody responses in merino sheep given three successive inoculations with Dermatophilus congolensis

Three antigens prepared from different phases of the life cycle of Dermatophilus congolensis were used in an enzyme-linked immunosorbent assay to measure serum and skin surface antibody responses in sheep after a first, second and third inoculation with D. congolensis. After the first inoculation, a strong antibody response to the flagella, filament and soluble antigens was detected after 7-21 days in the sera from sheep that were regularly biopsied; the antibody response at the skin surface was detected 28-42 days after inoculation, when the lesions were resolving. Strong anamnestic responses were detected in the serum of sheep that were biopsied and some of the nonbiopsied sheep after the second and third inoculations, but the skin surface antibody response at these times was variable.

Secretory component-dependent binding of immunoglobulin A in the rat, monkey and human: a comparison of intestine and liver

The source and significance of immunoglobulin A in bile remains controversial. In the rat, and several other species, immunoglobulin A is transported through hepatocytes by a specific receptor, secretory component. In humans, immunohistochemical methods have indicated a distinct lack of receptors for immunoglobulin A on hepatocytes. Binding assays with 125I-immunoglobulin A and membranes from hepatocytes and intestinal cells of the rat display secretory component-dependent binding. Primate intestinal cells also show secretory component-specific binding of immunoglobulin A. Primate liver, on the other hand, does not show immunoglobulin A binding mediated by the polymeric immunoglobulin receptor.