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PubMed1982

Immunohistochemical evaluation of carcinoembryonic antigen, secretory component, and epithelial IgA in ulcerative colitis with dysplasia.

Immunofluorescence staining for carcinoembryonic antigen, secretory component, and epithelial IgA was evaluated semiquantitatively in routine formalin-fixed mucosal biopsy samples from five patients with ulcerative colitis who had undergone colectomy because of carcinomas. Selected areas were given fluorescence intensity scores without knowledge of whether dysplasia or reactive hyperplasia was present as judged by another observer from conventional histopathological features in adjacent sections. The two types of lesion did not differ significantly with regard to the expression of the three marker antigens. In a prospective study based on cold ethanol-fixed mucosal biopsy samples, lesions from 11 ulcerative colitis patients with dysplasia were compared blindly with lesions from six patients with reactive hyperplasia and with samples obtained endoscopically from eight normal controls. The range of disease-associated fluorescence intensity scores was wide, but staining for all markers tended to be brighter in reactive hyperplasia than in dysplasia (P less than 0.01). In the controls, the fluorescence intensity score tended to be lower for carcinoembryonic antigen but was significantly (P less than 0.01) higher for secretory component and epithelial IgA than in both types of lesion. Moreover, staining for secretory component and epithelial IgA in the lesions seemed to be inversely related to the grade of dysplasia and the degree of inflammation. No such trend was seen for carcinoembryonic antigen. The wide ranges of individual fluorescence scores precluded the possibility of applying carcinoembryonic antigen, secretory component, and epithelial IgA as immunohistochemical markers to differentiate between dysplasia and reactive hyperplasia in routine diagnostic work.

Adolescent↗
PubMed1980

Serum secretory component level in myeloma patients with disorders of the secretory surface.

Secretory component (SC) in myeloma serum was measured by a double antibody radioimmunoassay. It was elevated in patients with IgA myeloma and the highest level was observed in a patient with macroglobulinemia. The presence of disorders of secretory surface in myeloma patients slightly but not significantly elevated the serum SC concentration. A significant correlation between serum SC and IgG is demonstrated, but not between serum SC and IgA. Over the whole patient groups, serum SC is significantly related to serum IgM but not when patients with macroglobulinemia are excluded from the calculation. Serum SC is present as SC-IgM in macroglobulinemia and SC-IgM and SC-IgA in IgA myeloma.

Humans↗
PubMed1977

Relative rates of the non-covalent and covalent binding of secretory component to an IgA dimer.

The rate of binding of free secretory component to an IgA dimer in vitro was studied by high-voltage gel electrophoresis at different times after mixing. The rate of the formation of the covalent component of the interaction (i.e. the disulphide interchange reaction) was monitored separately by denaturing the proteins in 6 M guanidine hydrochloride at different times after mixing and subsequently estimating the amount of covalently bound secretory componenet by gel chromatography in the denaturing solvent. The rates of the two reactions could not be distinguished in experiments at 37 degrees or 20 degrees C. At 4 degrees C, however, secretory component bound to the IgA dimer almost as rapidly as at higher temperatures, while the rate of the disulphide interchange was considerably lower. This indicates that the noncovalent interactions are the primary type of bonds formed between secretory component and IgA, and that the formation of these bonds initiate the disulphide interchange reaction, the rate of which is highly dependent on temperature.

Binding Sites, Antibody↗
PubMed1980

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.

Animals↗
PubMed1998

Secretory component production by human bronchial epithelial cells is upregulated by interferon gamma.

Secretory immunoglobulin A (S-IgA) participates in the first noninflammatory line of defence of the respiratory tract. S-IgA consists of dimeric IgA (dIgA) produced by plasma cells and secretory component (SC) produced by epithelial cells. This study compared SC production by primary cultures of human bronchial epithelial cells (HBEC) and by respiratory epithelial cell lines. Among the cell lines, A549 did not produce detectable SC, 16HBE produced very low levels of SC, while CALU-3 produced significant levels of SC. HBEC produced SC in nonpolarized and polarized primary cultures, where it was secreted apically. Polarized HBEC transcytosed radiolabelled and cold dIgA, resulting in the presence of S-IgA in their apical media. SC production and IgA transcytosis by polarized HBEC were upregulated by interferon-gamma (IFN-gamma) after 48 h. By reverse transcription-polymerase chain reaction, no SC messenger ribonucleic acid (mRNA) was detected in A549 and 16HBE, while SC mRNA in CALU-3 was comparable to that of HBEC incubated for 48 h with IFN-gamma. By immunocytochemistry, HBEC expressed SC immunostaining and its intensity increased after 48 h with IFN-gamma. It is concluded that human bronchial epithelial cells produce secretory component and transcytose dimeric immunoglobulin A in vitro. These processes were apically polarized and upregulated by interferon-gamma. Among the cell lines studied, only CALU-3 expressed secretory component-messenger ribonucleic acid and produced detectable secretory component.

Aged↗
PubMed1985

Fragmentation and reduction of bovine secretory component. Preparation of a biologically active fragment and some evidence for a multiple-domain structure.

A tryptic fragment (A) of Mr 25000 was prepared from bovine secretory component. The fragment binds polymeric immunoglobulin, although 9 times less effectively than secretory component on a molar basis. The fragment has four buried half-cystine residues and two exposed half-cystine residues. It gives rise to two fragments of Mr 11000-13000 on prolonged digestion with trypsin, and these do not bind polymeric immunoglobulin. It is proposed that fragment A consists of two immunoglobulin-like domains. Bovine secretory component was found to have 9-11 buried half-cystine residues and four exposed half-cystine residues. Reduction and alkylation of the exposed residues decreases the binding of polymeric immunoglobulin by 3-fold. Initial tryptic cleavage of bovine secretory component gives a fragment (Q) disulphide-bridged to a further fragment (T). Fragment Q is similar in size to a three-domain immunoglobulin fragment, and fragment T is similar in size to a two-domain immunoglobulin fragment. The two-domain fragment A is derived from fragment Q by further tryptic cleavage. The results are compatible with the proposal by Mostov, Friedlander & Blobel [(1984) Nature (London) 308, 37-43] that secretory component consists of multiple immunoglobulin-like domains. The results also indicate that optimal binding of polymeric immunoglobulin involves several domains stabilized by an exposed disulphide bridge.

Alkylation↗
PubMed1977

Distribution of immunoglobulin and secretory component containing cells in chickens.

Distribution of immunoglobulin (Ig)-containing cells and secretory component in internal organs of two 15-day-old embryos and 17 chickens, 1 to 480 days old, were examined by fluorescent antibody technique. In 15-day-old embryos, Ig-containing cells were not found in gut, bursa, spleen, or thymus. The bursa of Fabricius synthesized IgM, IgG, and IgA in as young as 1-day-old chicks. In extrabursal organs, IgM-containing cells were already present in intestine of 1-day-old chicks, but IgA-containing cells appeared in intestine, thymus, and spleen between the 3rd and 7th day after hatching. Very few IgG-containing cells were in intestine on the 3rd and 7th day after hatching. Secretory component was found in epithelial surfaces of intestine and ductus choledochus of most chickens examined. The presence of secretory component and IgA-containing cells in intestine supported the existence of secretory-immunologic system in chickens.

Animals↗
PubMed1998

Secretory component of immunoglobulin A in maternal serum and the prediction of preterm delivery.

OBJECTIVE: Our purpose was to determine whether the secretory component of immunoglobulin A in maternal serum predicts delivery before 34 weeks' gestation. STUDY DESIGN: Primigravid women of an urban population in New Zealand were recruited at booking into a prospective longitudinal nested case control study (n = 1651; after exclusions and withdrawals, n = 1511). Serum was collected at 8 to 12 weeks, 15 to 18 weeks, 21 to 24 weeks, 28 to 30 weeks, and 36 to 38 weeks of gestation and 6 weeks post partum. Concentrations of the secretory component of immunoglobulin A were determined by enzyme-linked immunosorbent assay in all women who were delivered preterm (n = 53) and in controls randomly selected from women delivered at > or =37 weeks' gestation (n = 178). RESULTS: Serum concentrations of the secretory component of immunoglobulin A were similar in women delivered at term or preterm throughout pregnancy (n = 21 delivered at <34 weeks and n = 32 at 34 to 36.9 weeks, incidence 3.5%). Receiver-operator characteristic curves showed no discriminating ability of the secretory component of immunoglobulin A. Smokers had 50% higher concentrations than nonsmokers did (p < 0.0001 by analysis of variance). CONCLUSION: The secretory component of immunoglobulin A in maternal serum does not predict preterm delivery in a low-risk population.

Adolescent↗
PubMed1970

Immunoglobulins, secretory component, and transferrin in eye secretions of infants in regions with and without endemic trachoma.

Eye secretions were collected from Boston and Saudi Arab infants between 1 day and 6 months of age. These secretions were then tested with monospecific antisera in double diffusion and immunoelectrophoresis for the presence of immunoglobulin (Ig)A, IgM, IgG, secretory component, and transferrin. (The term "secretory component" has been chosen by the World Health Organization to replace the terms "secretory piece" and "transport piece.") Eye secretions of all newborns contained secretory component. IgA was found attached to the secretory component in samples from some infants as young as 8 days of age and in samples from most infants over 3 weeks of age. IgG and transferrin were found in most samples regardless of the age of the infant. The prevalence of the respective proteins in the eye secretions of Boston infants was found to be similar to their prevalence in the eye secretions of Saudi Arab infants, including four who developed trachoma during the study. Specific antibody to trachoma was demonstrated in the eye secretions of those infants with active trachoma, and the immunoglobulin class was determined.

Journal Article↗
PubMed1979

[The "IgA secretory component complex" in bronchial mucus in patients with chronic obstructive lung disease under different therapy (author's transl)].

The concentration of "IgA secretory component complex" in the bronchial mucus was measured under different therapeutical influences. The "IgA secretory component complex" is a most important factor of the exogenous immunodefense. The formation of the "IgA secretory component complex" was independent from the age of the patients and from the intensity of their airway obstruction. Therapy with glucocorticosteroids and antibiotics had no certain influence on the formation of the immunocomplex. We did not find any certain influence of gammaglobulin therapy in adult patients with chronic airway obstruction, neither on the "IgA secretory component complex" nor on the immunoglobulin G, A and M. Furthermore, the clinical course of the disease was not influence by this therapy.

Adult↗
PubMed1992

Molecular cloning and exon-intron mapping of the gene encoding human transmembrane secretory component (the poly-Ig receptor)

Secretory component (SC or the poly-Ig receptor) plays a crucial role in mucosal immunity by translocating polymeric IgA and IgM through secretory epithelial cells into external body fluids. Labeled restriction fragments from human SC cDNA were used to screen a human genomic leukocyte library. Three overlapping clones, spanning a total of 19 kb of the human SC gene, including 3 kb of the 5' flanking region, were characterized. The putative TATA box candidate, preceded by a CAAT-like box, was found 329 nucleotides upstream of the first exon. Altogether 11 exons covering the entire coding region were identified. The exon size ranged from 59 to 657 nucleotides and exon-intron junctions followed known consensus sequences. Three of the five extracellular Ig-related domains (D1, D4 and D5) were confined to one exon each (E3, E5 and E6), whereas D2 and D3 were encoded by the same exon (E4). The latter exon corresponds to that involved in alternate splicing of rabbit SC. The membrane-spanning segment was confined to part of one exon (E8). The cytoplasmic tail was encoded by four exons (E8-E11), whose boundaries encompassed fairly well the structural determinants proposed to be responsible for intracellular sorting of SC in the rabbit. The polymorphic restriction site reported earlier for Pvu II was localized to the third intron.

Amino Acid Sequence↗
PubMed1984

[The primary structure of human free secretory component and the arrangement of disulfide bonds].

The amino-acid sequence and the arrangement of the disulfide bonds of the human free secretory component were completely elucidated by the methods of protein chemistry. The free secretory component is a monomeric glycoprotein (Mr approximately 86000), consisting of 558 amino acids with 7 carbohydrate chains bound to asparagine. The protein contains 20 cysteine residues but, as a special feature, no methionine. The polypeptide chain is divided into five regions of internal homology, 104 to 114 amino acids in length. The 20 cysteine residues form 10 disulfide bonds, 9 of which confirm the internal homology by their characteristic arrangement. The free secretory component also shows homology to immunoglobulins in some sections. A computer-supported tertiary structure is proposed for the free secretory component.

Amino Acid Sequence↗
PubMed2001

Binding of lactoferrin and free secretory component to enterotoxigenic Escherichia coli.

The ability of two glycoproteins of human milk, lactoferrin and free secretory component, to bind to Escherichia coli colonization factors (CFAs) was investigated using immunocytochemistry assays of enriched fimbrial extracts. The results revealed that lactoferrin binds to fimbrial CFA I adhesin but not to CFA II adhesin (CS1 and CS3), while free secretory component interacts with both CFA I and CFA II adhesins. Our data indicate that lactoferrin and free secretory component, which are very abundant proteins of human milk, could play an important role against infant enteric disease by blocking bacterial adhesion.

Bacterial Adhesion↗
PubMed1991

[Jejunal secretion of immunoglobulins and secretory component in three patients with primitive humoral immunoglobulin deficiency].

Jejunal secretion of albumin, immunoglobulins and secretory component was studied using the segmental perfusion technique with an occluding balloon, in two patients with common variable hypogammaglobulinemia and one patient with selective immunoglobulin A deficiency. Results were compared with those of twenty-two controls previously studied under the same conditions. In all three cases, jejunal secretion rate of immunoglobulin A was nil and secretion rates of albumin and immunoglobulin G were increased as compared to controls. Jejunal secretion rate of immunoglobulin M was increased in the patient with selective immunoglobulin A deficiency, normal in one case of common variable hypogammaglobulinemia and almost nil in the other case. Secretory component was secreted in the jejunal lumen mostly or exclusively under a free form depending on partial or total absence of immunoglobulin A and M. This study allowed to confirm in vivo that secretion of secretory component is independent of the presence of immunoglobulins. Intestinal perfusion might be a useful tool in the investigation of immunological diseases of the intestinal tract.

Adult↗
PubMed1998

Thiol-disulfide redox buffers maintain a structure of immunoglobulin A that is essential for optimal in vitro binding to secretory component.

We have shown that human secretory component (SC) binds in vitro to different samples of human and murine dimeric immunoglobulin A (IgA). The binding ratio in the IgA/SC complex is 1:1. IgA which is stably bound to SC is separated from unreacted IgA by anion exchange chromatography. A part of IgA/SC complexes formed in vitro is unstable to this elution; the proportion varies between different samples of IgA; it increases following prolonged incubation of IgA at 37 degrees C. Incubation of IgA with glutathione/glutathione disulfide (GSH/GSSG) redox buffers increases the proportion able to form a stable complex with SC to approximately 90%. The presence of bound SC is not essential for this process but does allow it to occur at a lower GSH/GSSG concentration. The stable IgA/SC complex consists of a structure with a disulfide bond between IgA and SC apparently in equilibrium with a structure in which this bond is absent. The proportion bound covalently is similar for different samples of IgA and is insensitive to incubation with GSH/GSSG. It is significantly greater for secretory IgA (sIgA) and for IgA and SC incubated together with a starting mixture of cysteine/cystine. Monoclonal, antigen-specific IgA, all of which is optimally bound to SC in essentially the same way as in native sIgA, can be isolated in high yield. Our results support a mechanism for optimal binding of IgA to SC, that can occur both in vitro and in vivo, in which a thiol disulfide interchange occurs between a free IgA thiol and a sensitive SC disulfide following the initial non-covalent interaction.

Anion Exchange Resins↗
PubMed1985

[Study on the local immune system of the human pancreas and liver--ultrastructural localization of IgA and secretory component].

The localization of IgA and secretory component (SC) in human pancreas and liver was studied by the peroxidase-labeled antibody method. Ultrastructurally, SC was found in perinuclear spaces, in endoplasmic reticulum, in saccules associated with Golgi complexes, on basolateral membranes, in endocytic invaginations and in cytoplasmic vesicles of the pancreatic epithelial cells and the biliary epithelial cells. IgA was found in subepithelial connective tissues, in basement membrane and on basolateral membranes, in endocytic invaginations and in cytoplasmic vesicles of the cells in which SC was visualized. From the above findings, we concluded that IgA was transported into pancreatic juice and bile by SC-mediated vesicular transport mechanism across the pancreatic epithelial cells and the biliary epithelial cells. The presence of local immune system in human pancreas and liver is assumed to be one of the principal factors that prevent severe infection after surgical operation for the organs.

Biological Transport↗
PubMed1981

Secretory component: a glandular epithelial cell marker.

Secretory component (SC) has been demonstrated to be produced by both normal and malignantly transformed glandular epithelial cells. By an indirect immunofluorescent technique, this study surveys tumors of varied cellular origin in order to determine the reliability of SC as a marker for tumor cells derived from glandular epithelium. Both primary and metastatic tumors of glandular epithelial origin demonstrated SC fluorescence, while nonglandular epithelial tumors did not. This observation was extended to live single-cell preparations, which demonstrated intense cell-surface fluorescence only when glandular epithelial tumors cells were examined. Additionally, fixed, cytocentrifuged, single-cell preparations of glandular epithelial tumors demonstrated cytoplasmic SC fluorescence. When breast carcinoma was examined, all cases demonstrated SC, regardless of the degree of differentiation. This assay appears to have useful clinical application in that the finding of SC provides indication of the glandular epithelial origin of a malignantly transformed cell.

Breast Neoplasms↗
PubMed1976

Bovine secretory component. Isolation, molecular size and shape, composition, and NH2-terminal amino acid sequence.

Bovine free secretory component was purified from whey by salt precipitation, gel filtration, DEAE-cellulose and phosphocellulose chromatography, and immunoadsorption. It was obtained in immunologically pure form and in 56% yield. The Stokes radius of pure free secretory component was found to be 4.3 nm by gel filtration, and an (see article) of 4.1 S was determined by the ultracentrifuge. The molecular weight was 79,000 by sodium dodecyl sulfate gel electrophoresis and by sedimentation dquilibrium in the ultracentrifuge, using a v of 0.73 determined by ultracentrifugation in D2O and H2O. A minimal axial ratio of approximately 5 was calculated. Amino acid analysis of bovine free secretory component showed remarkable similarity to that of human, dog, and rabbit but carbohydrate analysis showed significant differences. In contrast to the human, bovine free secretory compoennt has 2 methionine residues/mol. The NH2-terminal sequence was found to be Lys-Ser-Pro-Ile-PPHE-Gly-Pro-Glu-Glu-Val-Asp-Ser-Val. This sequence is identical with that the human and dog. However, the poor immunological cross-reactivity between the dog, human, and bovine proteins suggests that significant structural differences will be found in other regions of the molecule.

Amino Acid Sequence↗