CHARACTERISTICS OF AN IMMUNE SYSTEM COMMON TO CERTAIN EXTERNAL SECRETIONS

Human nasal respiratory secretions and host defense

The largest human body surface is the lining of the respiratory tract, gastrointestinal tract, and reproductive system each of which is covered by mucous membranes, named for their capacity to secrete mucus. Recent studies of mucus have defined some of the physiologic and pharmacologic controls of secretions. However, the constituents that are found in mucus and their roles in human health and disease are still in the initial phases of exploration. Human nasal respiratory secretions provide one convenient source of mucous membrane secretions. Nasal secretions include a variety of proteins, which appear to serve important functions in host-defense. Most, if not all, of the antiphlogistic products are synthesized and secreted by serous cells in the submucous glands, and it appears that the serous cell is the resident antimicrobial cell in mucous membranes.

The variability of immunoglobulins and albumin in salivary secretions of children

The variation of concentrations of immunoglobulins and albumin in consecutive daily collections of saliva was studied in 33 infants, aged 6 months to 5 years, for periods ranging from 16 to 26 days. The concentration and the within-child variability of IgA and albumin and the detection of IgG and IgM in saliva increased with age. Between-child variances were greater than the within-child variances by a factor of 2.8 for log (IgA) and 1.3 for log (albumin). The geometric mean IgA levels were consistently higher and IgG was detected more frequently during upper respiratory tract infections compared with periods of non-infection. There were no changes in albumin levels between infection and non-infection periods, suggesting a local immune response rather than serum leakage. There were significant within-child correlations (autocorrelations) between levels of IgA in saliva collected on consecutive days and samples collected up to 3 days apart. The autocorrelations between levels of albumin were significant for samples collected up to 2 days apart. The autocorrelation for IgA was significantly greater during infection periods compared with non-infection periods for samples collected on consecutive days.

Immunoglobulin A mediation of murine nasal anti-influenza virus immunity

Most mice which have recovered from influenza virus infection are immune to reinfection with the same influenza virus. This immunity could be abrogated by the intranasal instillation of anti-immunoglobulin A (anti-IgA) but not of anti-IgG or anti-IgM antiserum. Thus, IgA is the major, if not the sole, mediator of nasal immunity to influenza virus in immunocompetent mice.

Biodegradable microspheres as a vaccine delivery system

The utility of biodegradable and biocompatible microspheres as a vaccine delivery system for the induction of systemic and disseminated mucosal antibody responses was investigated. Intraperitoneal (ip) injection into mice of 1-10 microns microspheres, constructed of the copolymer poly(DL-lactide-coglycolide) (DL-PLG) which contained approximately 1% by weight a formalinized toxoid vaccine of staphylococcal enterotoxin B (SEB), dramatically potentiated the circulating IgG anti-toxin antibody response as compared to the free toxoid. The initiation of vaccine release was delayed in larger microspheres, and a mixture of 1-10 and 20-50 microns microspheres stimulated both a primary and an anamnestic secondary anti-toxin response following a single injection. However, neither free nor microencapsulated SEB toxoid induced a detectable mucosal IgA anti-toxin response following systemic injection. In contrast, three peroral immunizations with toxoid-microspheres stimulated circulating IgM, IgG and IgA anti-toxin antibodies and a concurrent mucosal IgA response in saliva, gut washings and lung washings. Systemic immunization with microencapsulated toxoid primed for the induction of disseminated mucosal IgA responses by subsequent oral or intratracheal (it) boosting in microspheres, while soluble toxoid was ineffective at boosting. These results indicate that biodegradable and biocompatible microspheres represent an adjuvant system with potentially widespread application in the induction of both circulating and mucosal immunity.

Both IgA subclasses are reduced in parotid saliva from patients with AIDS

Secretory IgA (SIgA), the isotypes IgA1 and IgA2, and IgM were measured by ELISA in stimulated parotid saliva from patients with AIDS (n = 16), subjects with asymptomatic HIV infection (n = 28), and HIV-seronegative healthy controls (n = 19). SIgA was significantly reduced in the AIDS group (10.4 micrograms/ml) compared with the asymptomatic HIV-infected subjects (17.1 micrograms/ml) and the controls (23.0 micrograms/ml). This decrease comprised both IgA1 and IgA2 to a similar extent on a relative basis. The SIgA decrease in AIDS patients was in striking contrast to their serum IgA level, which was significantly increased (6.9 g/l) compared with the asymptomatic HIV-infected subjects (2.9 g/l) as well as the controls (2.8 g/l). Low parotid output of SIgA in patients with HIV infection was associated with low numbers of CD4+ lymphocytes in peripheral blood as well as the presence of oral infections. The parotid output of IgM was similar in all groups. A low level of SIgA in the external secretions of patients with AIDS may well contribute to their frequent mucosal infections of opportunistic microorganisms.

Specific attachment of mesenteric IgA lymphoblasts to specialized endothelium of intestinal mucosa lamina propria capillaries

The bulk of IgA secreted in the gut is mostly contributed by locally dwelling plasma cells derived from B cells originating in the gut-associated lymphoid tissues (GALT). These IgA cells originate in Peyer's patches and recirculate, returning to the gut upon maturity. The precise mechanism of homing to secretory mucosae is to date not fully understood. It has been demonstrated, however, that specialized endothelium of small vascular spaces in peripheral nodes (PN) and endothelia of mucosal vessels are the site of receptor recognition for B and T cells. In their sojourn, IgA blasts have been shown to stop momentarily in mesenteric nodes (MN) before proceeding to their final destination, the lamina propria (LP) of the gut mucosa. They then develop into IgA-secreting plasma cells. In the present work, we show that IgA MN lymphoblasts, when compared to PN lymphoblasts, attach preferentially to LP venule and capillary endothelium, The B-cell maturation in the mesenteric lymph nodes, where IgA is the sole membrane-bound immunoglobulin, allows attachment of most of these cells. Our work suggests that the site of exit of IgA cells from the circulation are these specialized lamina propria venules and capillaries.

Distribution of immunoglobulins and secretory component in gastric cancer of the aged

The secretory immune system plays an important role in the local humoral immunity of the gastrointestinal tract. In order to evaluate humoral immunity in gastric cancer, distribution of immunoglobulins (Ig) and secretory component was immunohistochemically studied in 74 early and 15 advanced primary gastric cancers. In non-cancerous gastric mucosa, IgA and IgM, and secretory component were mainly identified in the cytoplasm of the intestinal metaplasia. In early gastric cancer of well-differentiated type, the localization of IgA and IgM, and secretory component was similar to that of intestinal metaplasia. In advanced gastric cancer, they were faintly observed and showed low positivity. The number of Ig-containing cells infiltrating cancerous stroma was enumerated. Immunoglobulin A-containing cells were dominant in the stroma of early gastric cancer. On the other hand, there were few Ig-containing cells in the stroma of advanced gastric cancer, and the number of IgA-containing and IgM-containing cells was also decreased. These results suggest that local humoral immunity is suppressed in gastric cancer, especially in advanced gastric cancer.

Anti-cholera toxin IgA-, IgG- and IgM-secreting cells in various rat lymphoid tissues after repeated intestinal or parenteral immunizations

Single antibody-secreting spot-forming cells (SFC) of the 3 main isotypes were counted in lymphoid cells from the gut lamina propria (LP), Peyer's patches (PP), mesenteric nodes (MN) and spleen (SP) of rats immunized 2-6 times intraduodenally (ID) or intraperitoneally (IP) with cholera toxin (CT). Responses for all isotypes peaked in all tissues after 4 ID- or IP-immunizations at much larger values than previously reported, and significantly decreased thereafter, except in LP and PP after IP-injections, where IgA- or IgG-SFC, but not IgM-SFC, only appeared or increased after 6 IP-doses. The highest IgA-SFC numbers (17% of tested cells) were in LP after 4 ID-doses. The isotype ratio was IgA greater than IgG greater than IgM in LP and PP after ID-injections, but IgG greater than IgA greater than IgM in MN and SP after both ID- and IP-routes. The isotype dispersion was much larger in LP and PP than in MN and SP. Our data show that at least 4 IP CT-doses were required to only elicit a few IgG- and almost no IgA-SFC in LP and PP, outlining the need for intestinal CT-immunizations to induce strong mucosal IgA-SFC responses. We also show good systemic responses elicited both by enteral and parenteral routes, and the small contribution of PP in total SFC, particularly after parenteral immunizations.

Humoral immune activity in CBA/Ca mice during late pregnancy and the post-partum period

Syngeneically mated CBA/Ca mice were used to measure "spontaneous" immunoglobulin (Ig) secretion in the Peyer's patches (PP), spleen and the para-aortic lymph nodes (PALN), employing a protein A plaque assay, during the latter part of pregnancy and in the post-partum period. The lactating and non-lactating females were compared with respect to humoral immune activity (plaque-forming cells) and serum Ig levels (ELISA technique). The pregnancy-induced weight changes in some lymphoid organs and the elevation in the number of plaque-forming cells in spleen (IgG and IgM PFC), PALN (IgG and IgM PFC) and the PP (IgA PFC) lasted longer in the lactating than in the non-lactating mice (owing to hormonal differences). A very strong decrease in serum IgG was observed during pregnancy and after parturition IgG levels remained depressed longer in lactating than in non-lactating mice. Interest has been focused on IgA in the study and this has been discussed as well as the possible reasons for the increased turnover of maternal serum Ig (especially IgG).

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.

Functional similarities of hepatic cystic and biliary epithelium: studies of fluid constituents and in vivo secretion in response to secretin

Hepatic cysts are a frequent manifestation of autosomal dominant polycystic kidney disease, but little is known about their functional characteristics. The goals of our study were to define the composition of hepatic cyst fluid and to determine whether hepatic cysts secrete in response to intravenously administered secretin. We percutaneously punctured five hepatic cysts and one proximal renal cyst from six subjects with autosomal dominant polycystic kidney disease and one solitary hepatic cyst from a subject without autosomal dominant polycystic kidney disease. Most fluids had an electrolyte composition similar to serum. Fluid from all hepatic cysts had glutamyltranspeptidase concentrations above those found in serum [( cyst]/[serum] = 4.93 +/- 5.92), contained secretory component (the epithelial receptor for polymeric IgA) and had glucose concentrations less than 15 mg/dl. Fluid from both hepatic and renal cysts of subjects with autosomal dominant polycystic kidney disease, but not from the subject with the solitary hepatic cyst, demonstrated extensive changes in the electrophoretic mobility of several serum proteins. Initial intracystic pressures ranged from 16 to 40 cm H2O, were reduced 57% to 97% after aspiration of a portion of cyst fluid and were held constant during the secretion study. Within 8 min of the intravenous administration of secretin, secretion of fluid increased in two of three hepatic cysts and in the renal cyst. The electrolyte composition of cyst fluids was not altered by secretin. These data suggest that hepatic cystic epithelium has functional characteristics of biliary epithelium and that secretion by both hepatic and renal cysts may be hormonally regulated.

The serum polymeric IgA antibody response to typhoid vaccination; its relationship to the intestinal IgA response

The relationship between the IgA antibody response in serum (total and polymeric IgA) and intestinal secretions was examined in volunteers subjected to oral and parenteral typhoid vaccination. After oral vaccination (three doses of 10(11) live Ty21a vaccine given at 48-hr intervals), serum pIgA antibody to typhoid lipopolysaccharide (LPS) was detected in seven of the 14 subjects (46.4 +/- 59 U/100 microliters, mean +/- SD). However, all 14 showed a significant intestinal IgA response (993 +/- 2516 and 9349 +/- 6754 U/mg pre- and post-vaccine; t = 5.25, P = 0.0002). The level of pIgA antibody declined rapidly, whereas intestinal IgA antibody levels remained elevated. Serum pIgA antibody was also found after parenteral immunization (two doses of 5 X 10(8) heat-killed bacteria given 14 days apart to six subjects), but an intestinal IgA antibody response was detected in these individuals only after a subsequent course of the oral vaccine given 1 month after initial parenteral immunization. Changes in serum pIgA antibody followed those of total serum IgA antibody rather than those of intestinal antibody. The results indicate that a serum pIgA response can be induced by an antigenic stimulus delivered either orally or parenterally, whereas an intestinal IgA response is induced only by a local antigen stimulus. The regulation of serum pIgA and intestinal IgA appear to be independent.

A study of secretory immunoglobulin A on membranous epithelial cells (M cells) and adjacent absorptive cells of rabbit Peyer's patches

Secretory immunoglobulin A (SIgA) on the surface of the membranous epithelial cell (M cell) is present in Peyer's patches, an important element of gut-associated lymphoid tissue (GALT). Little information about this immunoglobulin exists except for its scantiness inferred from electron microscopic examination of the relatively thin layer of glycocalyx on the cell surface. This study was undertaken to investigate SIgA on the M cell surface by immunohistochemical observations of specimens from 16-week-old rabbits, using anti-IgA antibody specifically directed to alpha-chain and anti-SIgA antibody specific to both alpha-chain and secretory component (SC). Areas of strongly positive reaction with these antibodies were demonstrable by electron, as well as light microscopy in the glycocalyx layer and on microfolds of M cells, contrasting with the glycocalyx layer and microvilli of the adjacent absorptive cells. The findings were suggestive of an abundant presence of SIgA in the glycocalyx layer and on microfolds of M cells. The results suggested the participation of SIgA on M cell surfaces through a mechanism in which M cells take up intestinal antigens, although the precise role of SIgA on M cells remains unclear.

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.

Otitis media in children: local immune response to nontypeable Haemophilus influenzae

Twenty children experienced 30 episodes of otitis media with effusion due to nontypeable (NT) Haemophilus influenzae in the first 2 years of life. The local and systemic immune responses to homologous strains of NT H. influenzae were determined by an immunodot assay. Strain-specific immunoglobulin G (IgG) antibody predominated in the middle ear fluid (MEF). It was detected in 91% of the children, compared with IgM in 48% (P less than 0.005), IgA in 52% (P less than 0.005), and secretory IgA in 18% (P less than 0.005). The titer (log2) of NT H. influenzae-specific IgG antibody (mean +/- standard error, 8.2 +/- 0.1) exceeded the titers of IgM (3.4 +/- 0.1), IgA (3.7 +/- 0.1), and secretory IgA (1.2 +/- 0.3). NT H. influenzae-specific antibody was detected exclusively in MEFs of individuals who possessed homologous serum antibody. Although antibody titers in MEF declined over time, serum antibody titers remained stable. These data suggest that immunity to NT H. influenzae in the middle ear, in part, reflects systemic immunity. Whereas local antibody disappears after resolution of the infection, systemic antibody persists.

Sialochemistry in Sjögren's syndrome: a review

Sjögren's syndrome (SS) is an autoimmune exocrinopathy. The salivary glands are the site of activated T- and B-lymphocytes, along with gradual parenchymal destruction, diminished flow and altered composition of the secretory product. At present, sialochemistry has achieved no significance for the evaluation of SS patient. However, the number of sialochemical publications is steadily growing. This study review current sialochemical findings in patients with SS and relate the observations to the present concept of diagnosis, pathogenesis and prognosis of SS. An ideal combination of the collection of low-stimulated pure secretion, measurements of absolute flow-rates, and biopsy from the same glands seem to be unobtainable in SS patients. But two procedures may be appropriate: stimulated parotid secretion combined with parotid biopsies, or absorbance of low-stimulated labila saliva combined with labial gland biopsy. Sufficient data on disease-specific alterations in salivary composition in SS are still lacking. However, detection of specific changes in protein synthesis or in glycosylation as well as the detection of inflammatory cell products should be possible with the use of sensitive biochemical assays.

Induction of antigen-specific IgA-forming cells in the upper respiratory mucosa

We investigated the actual processes for activating respiratory mucosal immunity. Hartley guinea pigs were immunized with particulate antigen of dinitrophenylated ovalbumin into the duodenum (group A), trachea (group B), and nasal cavity (group C) 1 week after systemic priming with the soluble antigen. The control animals (group D) received only systemic priming. Immunoglobulin A antibody titers in nasal secretions and saliva from groups A and B significantly exceeded those of groups C and D (p less than .01). Many antigen-specific IgA-forming cells were detected in the respiratory and gastrointestinal mucosae of groups A and B. Following duodenal immunization, the appearance of antigen-specific IgA-forming cells in Peyer's patches preceded those in mesenteric and hilar lymph nodes, while they simultaneously appeared in the lymphoid tissues after tracheal immunization. These findings suggest that intratracheal immunization mainly stimulates bronchus-associated lymphoid tissue as a source of IgA precursors, as intraduodenal immunization stimulates gut-associated lymphoid tissue.

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.

The ocular secretory immune system: a review

The majority of immunoglobulin in tears is of the immunoglobulin A (IgA) isotype, which is produced mainly by plasma cells of the lacrimal gland. The mechanism responsible for the lodging of the IgA cells in this gland is unknown and probably not dependent on direct glandular encounter with antigen. Previous experiments have suggested that a Th cell from the lacrimal gland can influence B lymphocytes to differentiate into IgA plasma cells. Mechanisms responsible for the IgA-specific Th cell accumulation in the LG could be related to nervous system influences, possibly neuropeptides. These effects on Th cells could be mediated either directly or through lacrimal gland epithelial cells. Such a mechanism could explain the presence of IgA-producing plasma cells in the lacrimal gland, and would allow strategies for manipulation of this important first line defense immune system.

Impaired gastrointestinal mucosal defense in Hirschsprung's disease: a clue to the pathogenesis of enterocolitis?

Twelve patients with Hirschsprung's disease were studied to investigate why some children develop enterocolitis. Previous studies have failed to explain this adequately; they have also failed to explain why enterocolitis can occur many years after definitive surgery. Six of the 12 patients had enterocolitis. By assessing immunological mucosal defense, it was shown that these patients had a marked deficiency in transfer of secretory IgA across the gastrointestinal mucosal cell, and thus were prone to mucosal invasion of both pathogenic and commensal organisms. The abnormalities were detected upon initial investigation (at presentation) prior to the onset of enterocolitis, and persisted into later life. The significance of these findings with reference to predicting which children are prone to develop enterocolitis and their long-term susceptibility to recurrence are discussed.

The liver and IgA: immunological, cell biological and clinical implications

Secretory immunoglobulin A is the characteristic and predominant immunoglobulin of the mucosal immune system; it participates in immunological protection at the level of mucous membrane surfaces. During the past 10 to 15 years, a great deal of experimental and clinical evidence has shown that the liver is very much involved in the sIgA system. In certain animals (rats, mice, rabbits), polymeric forms of IgA are efficiently cleared by the liver and transported into bile by a receptor-mediated vesicular pathway across hepatocytes. Taking advantage of this easily accessible pathway, investigators have defined many of the events in the external secretion of pIgA, including details about the synthesis and secretion of its receptor, secretory component. In the rat hepatocyte, secretory component is synthesized as a transmembrane glycoprotein and is expressed preferentially on the sinusoidal plasma membrane; circulating pIgA that binds to secretory component is internalized into endocytic vesicles and transported across the hepatocyte to the bile canalicular membrane, where the pIgA is released into bile as a soluble complex with a portion of the secretory component, the complex being secretory IgA. In some other animals (dog, guinea pig, sheep) as well as man, biliary epithelial cells, not hepatocytes, express secretory component and perform the transcytosis and secretion of pIgA into bile. In those species, much of the pIgA that reaches bile is synthesized locally in plasma cells that populate the biliary tree; this design is analogous to the release of sIgA into various mucosae in the body. The major biological functions ascribed to the secretion of IgA into bile are enhancement of immunological defense of the biliary and upper intestinal tracts and the clearance of harmful antigens from the circulation as IgA-antigen complexes. However, the importance of biliary IgA antibodies is largely unclarified, and man lacks the capacity for effective clearance of IgA-antigen complexes via the secretory component-mediated transhepatocellular pathway; whether this deficit contributes to the propensity for man to develop IgA immune complex diseases should be clarified. Among liver diseases, alcoholic disease is most closely linked to alterations in IgA metabolism. This association is manifested principally by the deposition of IgA along the sinusoids in the livers of the majority of alcoholics and in the renal mesangium of many.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of different vaccines and induced immune response against Campylobacter jejuni colonization in the infant mouse

The degree of protection conferred by vaccinated dams on infant mice against colonization by Campylobacter jejuni depended on the bacterial strain, preparation, and route of administration of the vaccine. In some instances of homologous protection, serum bactericidal titres correlated well with protection. However, boiled C. jejuni vaccine, which was non-protective, also elicited a strong bactericidal antibody response. Conversely, bactericidal activity could not be demonstrated against strains capable of cross-protection. There was a good correlation between high campylobacter-specific IgG response and bactericidal activity.

Molecular analysis of IgA in multiple sclerosis

IgA plays an important role in immune-mediated and anti-viral responses, and is the major antibody in external mucosal secretions. We used enzyme-linked immunosorbent assay (ELISA) and immunoblot to examine IgA in tears and parotid saliva of 21 multiple sclerosis (MS) patients and 19 normal controls. No significant difference in absolute levels were noted and both groups showed a wide range in values. However, 16 of 21 MS patients had detectable changes in molecular form of their IgA. Monomeric IgA was found in 52% of MS tears (P less than 0.001) and 45% of MS parotid saliva (P less than 0.05). Among normals, monomeric IgA was noted in only two saliva samples. IgA in secretions consisted of both A1 and A2 subclasses, although 14% of the monomeric MS IgA samples were restricted to a single subclass. Free secretory component was found in the secretions of all subjects with the exception of a single MS patient. However, immunoblot staining of secretory component was decreased in MS patients compared to controls. This study notes changes in IgA in two distinct external secretions in MS patients compared to controls. These changes are consistent with local mucosal inflammation. Impaired mucosal barriers have important implications in MS with regard to susceptibility to infectious agents, environmental antigen processing, and lymphocyte activation.

Molecular characteristics of IgA in infant saliva

Saliva was collected from 57 infants aged 6 weeks to 2.5 years and the molecular form of IgA was studied by centrifugation on sucrose density gradients. Two distinct populations were identified. Seventy-two per cent of the children had secretory IgA in their salivary secretions, while 28% had a molecular form corresponding to monomeric IgA. No samples with concurrent monomeric and secretory forms were detected. Monomeric IgA was not detected in any infant over 12 months of age. Secretory component was detected in all samples but was not associated with monomeric IgA. Forty-seven per cent of the samples contained IgA fragments of approximately 40,600 molecular weight. The presence of fragments dominated in the group of children with monomeric IgA. The presence of monomeric IgA in infant saliva did not result from degradation due to storage or proteolysis. The study demonstrated an apparent maturation sequence in the molecular form of IgA present in the salivary secretions of infants.

Vaccine-containing biodegradable microspheres specifically enter the gut-associated lymphoid tissue following oral administration and induce a disseminated mucosal immune response

Biodegradable and biocompatible microspheres have been investigated for their usefulness as a vaccine delivery system for both parenteral and enteral immunization. Microspheres composed of poly(DL-lactide-co-glycolide) which contained a toxoid vaccine of Staphylococcal enterotoxin B were found to strongly potentiate the circulating anti-toxin antibody response following intraperitoneal injection. Following oral administration, microspheres less than 10 microns in diameter were specifically taken up into the Peyer's patches of the gut-associated lymphoid tissue, where those greater than or equal to 5 microns remained fixed for an extended period. Microspheres less than 5 microns were disseminated within macrophages to the mesenteric lymph nodes, blood circulation and spleen. Oral immunization with enterotoxoid-containing microspheres induced circulating toxin-specific antibodies and a concurrent secretory IgA anti-toxin response in saliva, gut wash fluids and bronchial-alveolar wash (BAW) fluids. In contrast, soluble enterotoxoid was completely ineffective as an oral immunogen.

Biodegradable microspheres: vaccine delivery system for oral immunization

The potential of biocompatible and biodegradable microspheres as a controlled release oral vaccine delivery system has been examined. Orally-administered 1-10 micron microspheres composed of poly (DL-lactide-co-glycolide) were specifically taken up into the Peyer's patch lymphoid tissue of the gut, where those greater than or equal to 5 micron remained for up to 35 days. Microspheres less than 5 micron disseminated within macrophages to the mesenteric lymph nodes and spleen. In contrast to soluble staphylococcal enterotoxin B toxoid, oral immunization with enterotoxoid in microspheres induced circulating toxin-specific antibodies and a concurrent secretory IgA anti-toxin response in saliva and gut fluid.

Mucosal IgA elaboration

Secretory IgA is the main immunoglobulin present along mucosal surfaces. It is elicited best by oral rather than parenteral administration of specific antigens. The role of antigen form on the development of a secretory IgA response is still unclear. IgA protects by preventing attachment of microorganisms or their toxic products to the surface epithelium. A wide variety of regulatory T cells are now known to be of considerable importance in optimizing the secretory IgA response. This regulation is at least partly due to the elaboration of small polypeptide products (lymphokines). These lymphokines have been shown to be key signals during the maturation of IgA precursor B cells to IgA-secreting plasma cells. By studying models of the mucosal immune system which closely approximate the natural mucosal immune response, it should be possible to develop vaccines against many pathogenic microorganisms, their toxic products, and to toxicants and carcinogens within the environment.

Lateral diffusion of the secretory component (SC) in the basolateral membrane of the human colon carcinoma cell line HT29 assessed with fluorescence recovery after photobleaching

The lateral diffusion of the secretory component (SC), acting as a receptor for dimeric IgA in the basolateral side of intestinal epithelial cells, was studied in the human colonic carcinoma cell line HT29. The HT29 cells were grown in Dulbecco's modified Eagle's medium in which galactose had been substituted for glucose to promote development of small intestine-like cells, with a distinct separation of the basolateral side from the apical surface. The SC was stained with rhodamine-labeled polyclonal anti-human SC rabbit antibodies (Ig) or Fab fragments, and the lateral mobility was assessed with the fluorescence recovery after photobleaching technique. The average lateral diffusion was consistent with a diffusion constant of 7.7 +/- 2.0 (mean value +/- SD; n = 29) and 7.1 +/- 2.3 (n = 30) x 10(-10) cm2s-1 for Ig-and Fab-labeled receptors, respectively, which is slower than lipid diffusion but is similar to that found for other membrane receptors. The corresponding values for the fraction of mobile receptors were 66 +/- 13% and 71 +/- 12%, respectively. Cells were labeled from the top of the culture plate, and cells adjacent to a mechanically made rift or a natural opening in the cell monolayer were labeled more strongly, confirming the microscope-based impression that the basolateral surface primarily harboured the SC receptor.

Comparative studies on immunoglobulins, complement component (C3), albumin, and immunoglobulin A-containing circulating immune complexes in serum and bile of patients with biliary obstruction

We measured the concentrations of IgA, IgG, IgM, secretory IgA, albumin, complement component (C3), and IgA-containing circulating immune complex (IgA-CIC) in the serum and bile of patients with biliary obstruction. The bile-to-serum (BS) ratio of the concentrations of albumin and IgG increased with the increase in total serum bilirubin. This indicates that the permeability from blood to bile increases with the degree of biliary obstruction, and the blood-bile barrier function breaks down. The BS ratios of IgA and IgM, which are selectively secreted into bile, did not show a significant correlation with total serum bilirubin. The index of the BS ratio to the BS ratio of albumin (BS/BS-Alb index) of IgA and IgM was significantly larger than that of IgG. This indicates that the selective transport of IgA and IgM into bile is present even in patients with obstructive jaundice. Since the BS/BS-Alb index of C3 is larger than that of IgG, and the SGOT correlated directly with the BS ratio of C3, some of the C3 in bile may come from damaged hepatocytes.

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.

Sandwich-type ELISA for free and bound secretory component in human biological fluids

Three sandwich-type enzyme-linked immunosorbent assays (ELISA) are described for the measurement of free secretory component (SC) and SC bound to IgA (S-IgA) or IgM (S-IgM). These assays do not require preliminary fractionation of the biological fluids to be tested. The specificity of the assays is achieved with monoclonal antibodies specific for free SC (855 SC) and for SC bound to IgA or IgM (8545 SA). The amount of the three SC molecules in various biological fluids is reported. We demonstrate the presence of low levels of free SC in most of these fluids, including normal serum. Moreover our results suggest that S-IgM in serum may result from a non-covalent association between serum IgM and free SC.

Immunological functions of the gut--role of the mucosal immune system

This review summarizes recent information about immune responses in the intestinal mucosa with emphasis on the role of orally-administered antigens from the external environment. The intestinal mucosa provides an extensive surface for potential absorption of pathogenic environmental antigens, such as microbes, chemicals, and food. The intestinal mucosa is densely populated by IgA-producing plasma cells. The humoral immune responses to antigens in the intestinal mucosa are largely of the IgA class in secretory form (sIgA). This sIgA provides an immunological barrier to absorption of antigens on the mucosal epithelium and to penetration into the body. The cell-mediated immune mechanism is also equipped in the mucosal sites. In addition, the mucosal immune response induces hyporesponsiveness of nonmucosal (systemic) immune reactions, and the liver is an integral part of the mucosal immune system. Thus we consider that the mucosal immune system plays a central role in the maintenance of the homeostasis of the total immune system.

Circulating immune complex, endotoxin, and biliary infection in patients with biliary obstruction

Immunoglobulin A-containing circulating immune complexes, immunoglobulin G-containing circulating immune complexes, and endotoxin were measured in the sera of patients with obstructive jaundice. The bile of patients with percutaneous transhepatic biliary drainage was also cultured for bacteriologic studies. There was a significantly positive correlation between the endotoxin levels and both immunoglobulin A-containing circulating immune complex and immunoglobulin G-containing circulating immune complex. The endotoxin levels of the patients with gram-negative infections were significantly increased compared with those of the patients with sterile cultures. The immunoglobulin G-containing circulating immune complex levels of the patients with bacteria in bile were significantly increased compared with those of the patients with sterile cultures. The immunoglobulin A-containing circulating immune complex levels of the patients with bacteria in bile were slightly increased, but the difference did not reach statistical significance. These results indicate that one of the causes of increased circulating immune complex levels may be endotoxemia in combination with biliary infection in patients with biliary obstruction.

Enhancement of the humoral immune response and resistance to bacterial infection in mice by the oral administration of a bacterial immunomodulator (OM-89)

We investigated the effects of an Escherichia coli-derived product (OM-89) in mice. The oral administration of OM-89 led to a significant (p less than 0.05, Student's t test) increase in the levels of IgA in intestinal secretions, which was at maximum 25 days after the end of the treatment, when a two-fold increase in IgA levels was observed. The i.p. inoculation of OM-89 induced the stimulation of anti-SRBC plaque-forming cells (PFC) in the spleen. The effect of OM-89 was dose-dependent and produced up to a 9-fold increase in PFC in the treated mice when compared to untreated controls. The oral administration of OM-89 proved to be effective in the enhancement of resistance to challenge i.p. inoculation with E. coli. 32% of OM-89-treated mice showed resistance to this experimental infection at minimal LD100. The combined effects of low environmental temperature and cyclophosphamide (CY) immunosuppression enabled us to enhance differences in survival rates in experiments on the modulation of resistance towards Pseudomonas aeruginosa infection. The oral treatment with the immunomodulator induced a significant (p less than 0.05, Student's t test) level of protection in CY-immunosuppressed mice to the intranasal infection with P. aeruginosa, when mice were kept at low environmental temperature right after the bacterial challenge. The protective effect of OM-89 treatment was dependent on both the environmental temperature and the timing of the experiment.

Recent studies of the interaction of rabbit dimeric IgA with its polymeric immunoglobulin receptor

Rabbit secretory components (SC) constitute a highly heterogeneous population of glycoprotein molecules that are present in secretions as free or bound forms to polymeric immunoglobulins (Ig). Two SC families are known, one of high molecular weight (approximately equal to 80 Kd) composed of five (perhaps six) domains related to Ig variable domains, and one of low molecular weight (approximately equal to 55 Kd). An account of our most recent experimental data is reviewed in this article. We have shown: 1) that both the high and low Mr SC families possess the same relative avidity for binding to dimeric IgA of the g-subclass; 2) that the first NH2-terminal domain of SC derived from the high and low Mr polypeptides is necessary and sufficient for efficient non-covalent binding to dimeric IgA of the g-subclass; 3) that the low Mr SC polypeptide derives from the high Mr SC by the internal deletion of the entire second and third domains, suggesting that these domains are not involved in the binding reaction with polymeric Ig; 4) that the heterogeneity of rabbit secretory components is, in large part, due to the expression of several polymorphic forms (allotypes) susceptible to be recognized by specific alloantisera; the biochemical characterization of the three known SC allotypes (t61, t62 and t63) reveals that t62 and t63 are structurally very similar to each other and markedly divergent from the t61 homologue; 5) that by using non-cross-reactive alloantisera, the major immunodominant allotopes are confined within the COOH-terminal domains 3, 4 and 5 of SC; 6) that the location of the residues involved in the attachment of the carbohydrate unit within domain 1 varies according to the allotype: t61 is N-linked glycosylated at position 70, whereas about 75% of t62 molecules are devoid of sugars; the remaining 25% of t62 molecules are glycosylated at residue position 90; these oligosaccharide chain units are linked to asparagine residues in the acceptor site consensus sequence, Asn-X-Thr/Ser; 7) that the presence of the carbohydrate unit in domain 1 is not required for efficient binding of this domain to polymeric Ig: indeed, after enzymatic deglycosylation, domain 1 exhibits a relative binding avidity which is indistinguishable from that of the native glycosylated domain 1.

Total and specific immunoglobulin response to acute and chronic urinary tract infections in a rat model

Total and specific levels of immunoglobulins IgG, A and M were determined by an enzyme-linked immunosorbent assay (ELISA) in a rat model of urinary tract infections (cystitis) during the early and late phases of infection. The early response was characterized by rapid rise in IgM in serum and urine. This response decreased rapidly and was undetectable in urine after eight weeks. Correlation between total serum and urine levels of IgM was not found although a chronological relationship was observed. Total and specific serum and urine IgA responses were erratic. Concentrations of IgA were low and this antibody class was undetectable in urine until the infection had been established for six weeks. In contrast, total serum and urine IgG increased in concentration at five days post infection and reached total maximum by weeks four to eight, then declined, but remained detectable over 24 weeks. Specific IgG titers remained elevated in serum but declined in urine between four and 10 weeks. A correlation between total serum and total urine IgG was found. Also, bacteria generated a concomitant nonspecific response, a part of which was detected against a common antigen expressed on E. coli J5 strain that cross-reacts with a number of gram negative genera. The results show that IgM chronologically is the first antibody to appear in increased amounts in the serum and urine, followed by IgG. The data also suggests a relationship exists between total serum IgG and total urine IgG which may affect the host's ability to eliminate urinary infection.

Plasma levels of secretory IgA in patients with gastric cancer

The levels of plasma secretory IgA were measured in patients with gastric cancer and found to be slightly higher (9.6 +/- 6.2 micrograms/ml) than those in healthy controls (7.0 +/- 2.6 micrograms/ml, 0.05 less than P less than 0.1). Secretory IgA levels in those with hepatic metastases (19.7 +/- 12.2 micrograms/ml) were significantly higher than those in patients without hepatic metastases (P less than 0.001). In the latter, there was no significant relationship between plasma secretory IgA levels and the deepest layer of cancerous invasion or lymph node metastases. The secretory IgA levels in cases of well differentiated tubular adenocarcinoma were significantly higher than those with poorly differentiated adenocarcinoma (P less than 0.05). Although there is small diagnostic value in the detection of gastric cancer by measuring the levels of secretory IgA, high levels of secretory IgA in gastric cancer patients may be indicative of the presence of hepatic metastases.

Protective secretory immunoglobulin A antibodies in humans following oral immunization with Streptococcus mutans

Ingestion of a vaccine containing killed Streptococcus mutans, originally isolated from each volunteer, daily for 10 consecutive days induced increased levels of specific secretory immunoglobulin A (sIgA) antibodies to S. mutans cells and two cell surface proteins, glucosyltransferase and surface antigen I/II, in parotid saliva and tears of four healthy males and in parotid saliva, tears, colostrum, and milk of a pregnant woman. In addition, these antibodies inhibited glucosyltransferase activity. Both IgA1 and IgA2 antibodies were induced. The levels of IgA antibodies in all secretions remained significantly above preimmunization levels for more than 50 days after oral administration of antigen. A second series of immunizations for 7 consecutive days resulted in even higher levels of sIgA antibodies, which peaked earlier and persisted longer than those observed after the primary immunizations. No increase in levels of antibodies in serum were detected in any subject. Antibodies reactive with human heart and kidney antigens could not be detected in saliva, tears, colostrum, milk, or serum samples collected at any time during the immunization regimen. The numbers of viable S. mutans organisms in dental plaque and whole saliva decreased after each series of immunizations, which correlated with increased levels of IgA antibodies in saliva, suggesting that IgA antibodies in saliva were responsible for the reduced adherence of this bacterium. These results indicate that ingested S. mutans antigen induces secretion of specific IgA1 and IgA2 antibodies in saliva, tears, colostrum, and milk, providing further evidence for the existence of a common mucosal immune system.

Mucosal immunity: the immunology of breast milk

The mammary glands represent one part of the mucosal immune system, a definable, subunit of humoral and cellular immune functions in man that appears to have developed particular qualities well suited to guard our interface with the environment. As our understanding of secretory immunoglobulins and lymphocyte migration patterns continues to develop, the immunologic components found in breast milk appear increasingly likely to play a specific immunologic role in the protection of the nursing infant. The biologic basis for the observed protective effect of breast-feeding is reviewed with an emphasis on the mechanisms involved in the development and maintenance of mucosal immunity in general.

Transport defect of IgM into luminal space in selective IgA deficiency

This study explored the pathogenesis of a transport defect of IgM into the lumen in a patient with selective IgA deficiency. In addition to the absence of IgM in the saliva, no IgM was localized on the luminal surface of colonic mucosa from the patient despite the presence of J chain-positive IgM cells. On tissue sections, IgM cells did not bind secretory component. The serum IgM also showed a negligible capacity to bind secretory component in vitro. Such abnormalities of IgM molecules as stated above seem to be clinicopathologically linked with IgA deficiency or its associated Sjögren's syndrome.

A polymeric IgA response in serum can be produced by parenteral immunization

The magnitude and the kinetics of the serum-specific polymeric (p-) and monomeric (m-) IgA antibody responses were analysed following parenteral stimulation with tetanus toxoid (TT) vaccine in 10 volunteers, 5-20 years after a previous boost. A rapid marked serum IgA antibody response involving both the monomeric and polymeric components of IgA was observed: m-IgA and p-IgA antibodies reached a peak of serum activity at about 11 days, around 6 days before the peak of IgG antibody activity. At the peak of the IgA response, p-IgA accounted for approximately half of the anti-TT activity (median 54%, 25-79%). However, p-IgA antibodies rapidly disappeared from serum over a few weeks, whereas the serum m-IgA antibody response was maintained over a prolonged period of time. For one subject out of five, anti-TT IgA were also detected in saliva with a peak of activity earlier than in serum. Calculation of the albumin relative coefficient of excretion for anti-TT IgA in this saliva suggested a local synthesis of these antibodies. The present study indicates that a polymeric IgA antibody response in serum can be produced by parenteral immunization in primed individuals, and it raises the question of the mechanisms that control polymeric versus monomeric IgA production.

Immunoglobulin-producing cells in secretory immune system in patients with selective IgA deficiency

This study evaluated the class distribution and J chain-positivity of immunoglobulin-producing cells (Ig-PCs) in gastrointestinal mucosa and salivary glands of Japanese patients with selective IgA deficiency. The proportional patterns of gland-associated Ig-PCs showed an increase in not only IgM cells but also IgG cells, most of which were J chain-positive. This may represent a maturation arrest at B cell differentiation, rather than a compensatory phenomenon. No patients showed an increase of IgD cells in salivary glands. This behavior of IgD cells in Japanese patients may reflect associated diseases or ethnic difference in B cell differentiation.