CHARACTERISTICS OF AN IMMUNE SYSTEM COMMON TO CERTAIN EXTERNAL SECRETIONS

Immunoglobulin A secretion into pancreatic juice as a novel marker of local immune defense and exocrine pancreatic function

The importance of secretory immunoglobulin A (IgA) of local immune defense in the gastrointestinal tract has gained increasing acceptance. Bacterial contamination is a major factor related to mortality in acute pancreatitis. However, very little is known about IgA in pancreatic juice. Pure pancreatic juice was collected from 40 patients undergoing pancreatoduodenectomy. The patients were divided into three groups according to the degree of preoperative pancreatic duct obstruction, as follows: normal, narrowed, and obstructed. IgA concentration, amylase activity, and daily volume of pancreatic juice were measured. Daily IgA secretion into pancreatic juice was constant during the early period after the operation. The concentration of IgA in the control group was 5 +/- 0.8 microg/ml, and IgA daily secretion was 1.2 +/- 0.2 mg/day. Pancreatic duct obstruction resulted in a marked decrease in both amylase and pancreatic juice secretion. The concentration of IgA, however, was markedly increased in the narrowed group (11.1 +/- 2.4 microg/ml) and the obstructed group (32.5 +/- 5.4 microg/ml). The concentration of amylase increased with the increase in pancreatic juice. Conversely, the concentration of IgA increased with the decrease in volume of pancreatic juice. Similarly, the increased in IgA concentrations positively correlated with the decrease in amylase activity. In conclusion, the mechanisms that modulate IgA secretion in the human pancreas are essentially different from those that modulate digestive enzyme and fluid secretion. IgA in pancreatic juice may play an important role in pathological conditions such as pancreatic duct obstruction. As such, the measurement of IgA in pancreatic juice may potentially be used as a new marker of local immune defense and exocrine pancreatic function.

Lung mucosal immunity: immunoglobulin-A revisited

Mucosal defence mechanisms are critical in preventing colonization of the respiratory tract by pathogens and penetration of antigens through the epithelial barrier. Recent research has now illustrated the active contribution of the respiratory epithelium to the exclusion of microbes and particles, but also to the control of the inflammatory and immune responses in the airways and in the alveoli. Epithelial cells also mediate the active transport of polymeric immunoglobulin-A from the lamina propria to the airway lumen through the polymeric immunoglobulin receptor. The role of IgA in the defence of mucosal surfaces has now expanded from a limited role of scavenger of exogenous material to a broader protective function with potential applications in immunotherapy. In addition, the recent identification of receptors for IgA on the surface of blood leukocytes and alveolar macrophages provides an additional mechanism of interaction between the cellular and humoral immune systems at the level of the respiratory tract.

Increases of IgA milk concentrations correlate with IgA2 increment

IgA, IgA1, and IgA2 concentrations were determined in 81 defatted human milk samples: colostrum (days 1-5, n = 42), transitional milk (days 6-14, n = 18) and mature milk (days 15-75, n = 21) by immunonephelometry. Correlations were found between total IgA levels and the concentrations of both IgA subclasses (P < 0.0001). The levels of the three molecules decreased over lactation with significant differences (P < 0.05) between colostrum and transitional milk levels and between colostrum and mature milk. Colostral IgA1 and IgA2 mean concentrations dropped respectively from 10.89 +/- 2.12 g/L, and 15.41 +/- 2.10 g/L to 1.83 +/- 0.73 g/L and 3.40 +/- 1.25 g/L in transitional milk reaching finally to 0.36 +/- 0.07 g/L and 0.27 +/- 0.06 g/L in mature milk. IgA2 concentrations were higher than those of IgA1 when the total IgA level was high. The IgA2 levels in colostrum could be an adaptation resistance of IgA to potentially harmful pathogens able to secrete IgA proteases and also a way to regulate colonization of the microflora in the newborn.

Mucosal immunity and primary biliary cirrhosis: presence of antimitochondrial antibodies in urine

We have shown that IgA-class antimitochondrial autoantibodies (AMA) can be detected in the bile and saliva of patients with PBC, suggesting that AMA are secreted into the luminal fluid across bile ducts and salivary glands. These data prompted us to determine whether AMA of the IgA isotype may be transported across other epithelial mucosa. Therefore, we tested for the presence of AMA in the urine specimens of 83 patients with PBC and 58 non-PBC controls including healthy individuals and patients with other liver diseases. Patients enrolled in this study had no history of renal disease, and we confirmed there was less than 50 microgram/mL of protein in each of the urine specimens. Interestingly, we found that AMA were present in the urine of 71/83 (86%) of all patients with PBC and in 71/78 (91%) of patients with PBC that were serum AMA positive. In contrast, AMA were not detected in any of the 58 control urine specimens. Of particular interest, AMA of the IgA isotype was present in 57/83 (69%) of patients with PBC, and in 52 of these 57, we found secretory-type IgA. In a nested random subgroup of urine samples, the prevalence of the IgA2 AMA was 6/18 (33%), significantly lower than in matched serum samples, 13/16 (81%, P =.007). These data show that AMA of the IgA isotype is secreted into urine from the uroepithelium of patients with PBC, and support the thesis that PBC originated from either a mucosal challenge or a loss of mucosal tolerance.

Does low IgA in human milk predispose the infant to development of cow's milk allergy?

We sought a relationship between total and cow's milk-specific IgA levels in colostrum and human milk and subsequent development of cow's milk allergy (CMA) in the breast-fed infant. The study included 87 nursing mothers and their infants (age, 2 d to 7 mo), followed prospectively up to 1 y. At 1 y, 48 mothers (69% with an atopic constitution) had an infant with CMA, verified by clinical cow's milk challenge, eight (38% with an atopic constitution) had a baby who had had protracted infantile colic but no CMA (disease control group), and 31 (23% with an atopic constitution) had a healthy infant. Total breast-milk IgA was measured by radial immunodiffusion, and IgA antibodies to cow's milk were measured by ELISA during the breast-feeding period. The levels of total and cow's milk-specific IgA antibodies in colostrum and human milk were significantly lower in the mothers whose baby later developed CMA [estimated third day value, 0.38 g/L (95% confidence interval, 0. 24-0.82)] than in the ones whose infant remained healthy or had had infantile colic but not CMA [0.82 g/L (95% confidence interval, 0. 99-1.51); p < 0.05]. The infants developed CMA significantly more often if the concentration of total IgA antibodies in milk was <0.25 g/L, when measured between 6 d and 4 wk postpartum [sensitivity, 0. 55; specificity, 0.92; odds ratio, 14.7 (95% confidence interval, 3. 1-70.2); p < 0.001]. The levels of cow's milk-specific IgA positively correlated with the levels of total IgA but not with the development of CMA in the infant. The levels of total or cow's milk-specific IgA did not correlate with maternal atopy. IgA antibodies in colostrum and human milk may prevent antigen entry at the intestinal surface of the breast-fed infant. A low IgA content in human milk may lead to defective exclusion of food antigens and thus predispose an offspring to develop food allergies.

Subglottic airway becomes stable with age in the human infant larynx

Development of the mucosal defence system and its relationship to the pathogenesis of laryngeal diseases was studied by examining the changes in the laryngeal structures at the level of subglottic larynx of 59 human infants who died within 1 year of birth. By making a transverse section at the level of the cricoid cartilage, the area and diameter of each subglottic structure were examined using an image analysis system. The results were analysed, not only by their age at death, but also based on the total development score. The areas of the whole structure, cricoid ring, subglottic mucosa and inner cavity (available area) increased in close correlation with the total development score. In contrast to the increased diameter of the inner cavity, the thickness of the mucosa was almost the same size. These results indicate the stability of the subglottic airway with advancing age in the human infant larynx.

The B-cell system of human mucosae and exocrine glands

The mucosae and exocrine glands harbour the largest activated B-cell system of the body, amounting to some 80-90% of all immunoglobulin (Ig)-producing cells. The major product of these immunocytes is polymeric (p)IgA (mainly dimers) with associated J chain. Both pIgA and pentameric IgM contain a binding site for the polymeric Ig receptor (pIgR), or secretory component (SC), which is a requirement for their active external transport through secretory epithelia. The pIgR/SC binding site depends on covalent incorporation of the J chain into the quaternary structure of the polymers when they are produced by the local immunocytes. This important differentiation characteristic appears to be sufficient functional justification for the J chain to be expressed also by most B cells terminating at secretory effector sites with IgD or IgG production; they probably represent a "spin-off" from sequential downstream CH switching on its way to pIgA expression, thus apparently reflecting a maturational stage of effector B-cell clones compatible with homing to these sites. Observations in IgA-deficient individuals suggest that the magnitude of this homing is fairly well maintained even when the differentiation pathway to IgA is blocked. Certain microenvironmental elements such as specific cytokines and dendritic cells appear to be required for induction of IgA synthesis, but it remains virtually unknown why this isotype normally is such a dominating product of local immunocytes and why they have such a high level of J chain expression. Also, despite the recent identification of some important requirements in terms of adhesion molecules (e.g. integrin alpha 4 beta 7 and MAdCAM-1) that explain the "gut-seeking" properties of enterically induced B cells, the origin of regionalized homing of B cells to secretory effector sites outside the gut remains elusive. Moreover, little is known about immune regulation underlying the striking disparity of both the class (IgD, IgM) and subclass (IgA1, IgA2, IgG1, IgG2) production patterns shown by local immunocytes in various regions of the body, although the topical microbiota and other environmental stimuli might be important. Rational design of local vaccines will depend on better knowledge of both inductive and migratory properties of human mucosal B cells.

Production and characterization of recombinant IgA

Existence of secretory immunity at the mucosal surfaces was first postulated in 1919. Since then experimental and clinical studies have indicated that it is immunoglobulin A (IgA) that provides the first line of immune defense at the mucosal surfaces. While a number of expression systems--including viral, plant and mammalian cells--have been used to produce recombinant IgA, we used the mammalian expression system to produce IgA1 and the three allotypes of IgA2. By introducing the gene coding for human secretory component (SC) into transfectants producing IgA1, we have generated a single mammalian cell system that produces covalently assembled secretory IgA (sIgA). Using pulse-chase analysis, we determined the covalent assembly pathways of IgA1, IgA2 and sIgA and identified some of the structural differences leading to the different assembly patterns. Using affinity purified proteins, we have shown that neither IgA1 nor any of the allotypes of IgA2 activate either the classical or the alternative complement pathways, but modulate the complement activity of IgG or IgM. The two N-linked glycosylation sites in IgA1 are not required for its binding to the polymeric Ig receptor (pIgR). Finally, we have shown that sIgA1 was more stable than dIgA1 in the gastrointestinal tract of mice, suggesting that SC provides resistance to IgA in the gastrointestinal tract.

Current status of a mucosal vaccine against dental caries

The evidence of a specific bacterial cause of dental caries and of the function of the salivary glands as an effector site of the mucosal immune system has provided a scientific basis for the development of a vaccine against this highly prevalent and costly oral disease. Research efforts towards developing an effective and safe caries vaccine have been facilitated by progress in molecular biology, with the cloning and functional characterization of virulence factors from mutans streptococci, the principal causative agent of dental caries, and advancements in mucosal immunology, including the development of sophisticated antigen delivery systems and adjuvants that stimulate the induction of salivary immunoglobulin A antibody responses. Cell-surface fibrillar proteins, which mediate adherence to the salivary pellicle, and glucosyltransferase enzymes, which synthesize adhesive glucans and allow microbial accumulation, are virulence components of mutans streptococci, and primary candidates for a human caries vaccine. Infants, representing the primary target population for a caries vaccine, become mucosally immunocompetent and secrete salivary immunoglobulin A antibodies during the first weeks after birth, whereas mutans streptococci colonize the tooth surfaces at a discrete time period that extends around 26 months of life. Therefore, immunization when infants are about one year old may establish effective immunity against an ensuing colonization attempts by mutans streptococci. The present review critically evaluates recent progress in this field of dental research and attempts to stress the protective potential as well as limitations of caries immunization.

Salivary SIgA and SIgA 1 in coeliac disease, inflammatory bowel disease and controls

Levels of secretory IgA1 (SIgA1) in the saliva have not been measured previously in either coeliac disease (CD) or inflammatory bowel disease (IBD). Saliva was collected from coeliacs, IBD patients and controls. The concentration of total SIgA in saliva was measured by enzyme linked immunosorbent assay (ELISA) with an anti-human SIgA antibody as the bound phase and human SIgA isolated from colostrum as the standard. The concentration of SIgA1 was determined using an ELISA with a lectin with a high affinity for human SIgA1. The IBD patients have a significantly higher concentration of SIgA1 than the controls. The rate of secretion of saliva and %SIgA1 was significantly lower in coeliacs than in the control and IBD groups. The rate of secretion of SIgA1 was significantly higher in the IBD than in the coeliacs. We describe hitherto unreported levels of SIgA1 in CD and IBD.

Inflammatory bowel disease. 1. Origins, presentation, and course

The exact cause of inflammatory bowel disease remains undiscovered, but its destructive nature is clearly recognized. In this article, the authors summarize what is known about the pathogenesis and epidemiology of ulcerative colitis and Crohn's disease and how to distinguish between the two, both clinically and pathologically. They also describe disorders that may mimic inflammatory bowel disease. In part 2 of this article, beginning on page 86, the authors discuss some of the therapeutic options that are the commonly used as well as some that are investigational but show promise for patients with this chronic and relapsing disease.

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.

Induction of antigen-specific antibody-secreting cells in the nasal mucosa by intranasal immunization of BALB/c mice

Recent studies have demonstrated that antigen-specific IgA immune responses in nasal cavity are induced by intranasal immunization with several antigens. However, the precise mechanisms regulating such immune responses are unclear. In the present study, mice were immunized intranasally with horseradish peroxidase (HRP) plus cholera toxin into the right nostril, and HRP-specific IgA immune responses were investigated. After the immunization, an enzyme-linked immunospot assay showed an increased number of anti-HRP IgA cells in the nasal mucosa. Histochemical staining demonstrated the presence of anti-HRP antibody-secreting cells, mainly in the nasal subepithelial layer. Interestingly, these cells were induced predominantly on the right nostril, where intranasal immunization was performed. These findings suggest that antigen-specific IgA antibodies in the nasal secretions were produced locally from antibody-secreting cells in the nasal mucosa and that IgA immune responses in the nose were compartmentalized. Furthermore, lectin histochemistry showed an accumulation of peanut agglutinin-positive cells in the nasal-associated lymphoreticular tissue, suggesting the development of germinal centers in the immunized animals.

IgA nephropathy--human disease and animal model

IgA nephropathy is one of the most common chronic glomerulonephritides worldwide. Since the first publication on IgA nephropathy, a number of clinical and pathological investigations have revealed that the clinical course of patients with IgA nephropathy is extremely diverse, with approximately 10-20% of the patients developing end-stage chronic renal failure. Glomerular changes similar to IgA nephropathy have also been observed in patients with Schoenlein-Henoch purpura, and with other diseases such as liver cirrhosis and chronic inflammatory diseases of the lung. The broad spectrum of clinical and pathological features of IgA nephropathy encompasses a syndrome which includes both primary and secondary IgA nephropathy. The common etiology and pathogenesis of primary and secondary IgA nephropathy appear to be closely related to immunological abnormalities in the production of IgA induced by antigenic stimulation of the common mucosal immune system. IgA is one of the most important humoral factors of the mucosal immune defense system and functions as an antibody against various extrinsic and intrinsic substances. This review describes the Arthus type of IgA immune complex deposition in the glomeruli which can result from persistent or repeated increases in circulating IgA immune complexes. The latter occurs as a consequence of overproduction of IgA antibodies and/or impairment in clearance of IgA immune complexes by the mononuclear phagocytic system. The present review also focuses on the biology of the IgA-mediated immune system and on the etiology, pathogenesis, and animal models of IgA nephropathy.

Immunoglobulin-coated bacteria on the tonsillar surface during infectious mononucleosis

Sequential bacterial samples were obtained from the tonsillar surface of 19 consecutive patients (12 females, seven males; mean age 16.1 years, range four to 24 years) suffering from infectious mononucleosis with membranous tonsillitis. The specimens were examined with respect to aerobes (culture on blood and chocolate agar plates) and proportions of bacteria coated with immunoglobulins (secretory IgA, IgG, IgM) by using an immunofluorescence assay. In the early stage of the membranous tonsillitis phase, attachment of secretory IgA (SIgA) and IgG to the bacteria was greatly suppressed, as compared with healthy controls. Coating with IgM was evident only late in the membranous tonsillitis phase but was contracted and still evident even after the clinical throat symptoms had abated. The findings suggest that the B-lymphotropic Epstein-Barr virus, causative agent of infectious mononucleosis, exerts a transient suppression of immunoglobulin-coating of bacteria harboured on the tonsillar surfaces, with consequent abundant bacterial attachment to the epithelial cells and massive bacterial colonization on the palatine tonsils.

Population changes in immunoglobulin-containing mononuclear cells in dextran sulfate sodium-induced coltitis

To investigate the relation of immunoglobulin-containing cells in the colonic mucosa to mucosal inflammation, we immunohistochemically examined the localization of immunoglobulin-containing mononuclear cells in the lamina propria in dextran sulfate sodium induced colitis in mice. Mice were treated repeatedly with 3% dextran sulfate sodium (MW 54,000) solution or distilled water for a total of 170 days (chronic model), or for 85 days (subacute model) or for 10 days (acute model). IgG, IgA, and IgM-containing mononuclear cells were studied by enzyme immunostaining. The number of IgA- and IgG-containing cells gradually and significantly increased in the acute, subacute, and chronic models, in that order (P < 0.01 or 0.05). However, the numbers of IgM-containing cells in the three models were similar to that in the controls. These findings resembled those of human ulcerative colitis. In this dextran sulfate sodium-induced colitis, IgA-containing mononuclear cells may play an essential role in the mucosal immune system is the acute, subacute, and chronic phases. The finding that IgG-containing mononuclear cells increased substantially in the chronic phase suggests that IgG plays an important role in the mucosal inflammatory reaction during the chronic phase.

History of oral tolerance and mucosal immunity

Mucosal immunity depends on antigen stimulation in specialized lymphoepithelial structures such as the Peyer's patches. Although these inductive compartments were discovered more than 300 years ago, their functional role has become clear only over the last few decades. Research on homing of primed lymphoid cells to the intestinal mucosa began with animal experimentation in the 1960s and 1970s and has recently been brought to the molecular level. The major effector substance of mucosal immunity is secretory IgA (SIgA). The first evidence for its local antibody activity was obtained in humans in 1922, but its unique properties were not defined until the mid-1960s. Several models were subsequently proposed for selective external transport of IgA involving the secretory component (SC). In the early 1970s SC was suggested to act as a transmembrane polymeric Ig receptor common for dimeric IgA and pentameric IgM; this transport mechanism has now been confirmed by detailed studies at the level of cellular/molecular biology. Although SIgA antibodies performing immune exclusion are the main goal for exploitation of the mucosal immune system by oral vaccination, little is known about the precise mechanisms for induction of mucosal immunity against soluble proteins and chemicals. A peripheral immunosuppressive effect of oral immunization with such substances was apparently exploited by ancient people, and "oral tolerance" has since 1910 been subjected to numerous feeding experiments in rodents. The basis for the whole phenomenon appears to be intact epithelial barrier. Mucosal induction of suppression may in the future be exploited not only to modulate autoimmune diseases through the gut but also to prevent the development of IgE-mediated allergy and other untoward immune reactions by way of the respiratory tract.

Spondylarthropathies: from gut to target organs

Recent studies strongly support the concept that gut and joint inflammation are closely related. Progress also has been made in identifying individual mechanisms that contribute to the pathogenesis of joint disease in IBD and in undifferentiated SpAs. However, the interrelationship of these mechanisms that result in chronic disease manifestations at a site distant from the initiating event remain to be elucidated. The local absence of homing molecule receptors in the gut wall combined with an expression of these receptors in target organs can be responsible for the transformation of the synovial membrane and/or the enthesis into an aberrant tertiary lymphoid organ of the gut.

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)

Homogenous IgA monomers, dimers, trimers and tetramers from the same IgA myeloma serum

Starting from two IgA1 myeloma sera, the isolation of monoclonal monomeric, dimeric, trimeric and tetrameric IgA in a high state of purity and size homogeneity for each serum is described. The method combined repetitive gel filtrations on Ultrogel AcA22 with affinity chromatography on Jacalin-Sepharose. These various forms of pure polymeric IgA obtained from the same monoclonal IgA should allow a precise comparison of their respective structure and reactivity with different IgA-binding proteins, such as IgA Fc-receptors, the polymeric Ig receptor, and lectins.

Sheep red blood cell instillation at palatine tonsil effectively induces specific IgA class antibody in saliva in rabbits

We have shown that the palatine tonsil effectively incorporates exogenous foreign substances instilled at its surface. It is not clear whether antigen-specific IgA can be induced by the instillation. Sheep red blood cells (SRBC) were instilled at the palatine tonsil every three days as the antigen, and the agglutination titer of specific IgA in saliva was examined. Nasal or intragastric administration, which have been shown to induce specific antibody in saliva, were done as control experiments. Anti-SRBC antibody in saliva from the tonsillar instillation group was detected in the second week, and the agglutination titer reached a maximum in the 6th week after instillation. The maximum titers in the tonsillar instillation group and nasal administration group were 16 (P < 0.01, n = 7) and 4 times (P < 0.01, n = 7) higher, respectively, than that in the intragastric administration group. In the tonsillar instillation group, the number of specific antibody- producing cells per 10(5) lymphocytes was the highest in the parotid glands compared with the lymphoid tissues such as the retropharyngeal lymph nodes, nasal mucosa, mesenteric lymph nodes, Peyer's patches, cervical lymph nodes, palatine tonsil and spleen. In the nasal administration group, the number of lymphocytes was the highest in the nasal mucosa. The results indicate that tonsillar instillation was more effective than nasal administration in inducing specific iIgA in saliva.

Purification and measurement of secretory IgA in mouse milk

An important factor limiting better understanding of the protective role of sIgA at mucosal surfaces is the limited availability of the purified immunoglobulin. Among other things, purified sIgA is needed for use as a standard in measurements of the concentration of this immunoglobulin in mucosal secretions, particularly in mice, where several models of mucosal infections are available. We describe here a simple method by which one can obtain a mean of 3.5 ml of milk per mouse without a breast pump. Immunoblotting studies after native PAGE demonstrated that the milk contained mainly 420 kDa dimeric sIgA and higher polymeric forms of sIgA; only a trace of monomeric IgA was present. Similar immunoblotting studies after SDS-PAGE revealed that a portion of the sIgA was dissociated by this treatment. The 420 kDa sIgA was purified by salt fractionation, gel filtration, and affinity chromatography, and the purity of the final product was demonstrated by immunoblot analysis of biotinylated polypeptides after reduction of biotinylated protein. The concentration of 420 kDa sIgA in whey was measured by densitometry of immunoblot bands, using the purified 420 kDa sIgA as a standard, and found to be 1.0 +/- 0.3 mg/ml.

Presence of secretory IgA antibodies to an enteric bacterial pathogen in human milk and saliva

The concept of a common mucosal immune system in man was tested by examining the concurrent presence of specific-secretory IgA (SIgA) antibodies in human milk and saliva from three groups of subjects: 64 Sri Lankan women living in Sri Lanka; 20 immigrant Asian women living in Birmingham (median duration of residence in the United Kingdom five years); and 75 Caucasian women living in Birmingham (controls). Enzyme linked immunosorbent assays (ELISA) were developed to detect enterotoxigenic Escherichia coli (ETEC) colonisation factor/1 (CFA/1) specific SIgA antibodies in milk and saliva. ETEC CFA/1 specific SIgA antibody activity was detectable in milk (37.5% and 25%) and saliva (42.1% and 35%) of Sri Lankan and immigrant Asian women, respectively, but not in any of the Caucasian controls. Eighty five point two per cent of subjects who were positive had specific antibodies detectable in both milk and saliva; 5% of all Sri Lankan women and 10% of all immigrant Asian women had detectable antibody only in saliva. These observations lend further strong support to the idea that a common mucosal immune system exists in man. The continuing presence of specific SIgA antibodies in Asian immigrants to previously encountered antigens suggests that there may be an 'immunological memory' in the human secretory immune system.

The significance of the human endolymphatic sac and its possible role in Menière's disease

Modern immunohistochemical methods allow a functional characterization of the human endolymphatic sac (ES) and its associated cell populations. The currently available immunohistochemical data of the extraosseous part of the human ES support the assumption that the epithelium is metabolically active and capable of both secretion and adsorption. The reactivity of the epithelial cells with antibodies against neuroendocrine antigens imply a paracrine activity of the human ES. Further results provide evidence for a possible role of the human ES in inner ear immune defence and indicate a putative functional relationship of the human ES to the common mucosa-associated immune system (MALT).

Rapid and constant detection of HIV antibody response in saliva of HIV-infected patients; selective distribution of anti-HIV activity in the IgG isotype

Anti-HIV antibodies can be specifically detected with a sensitivity and a specificity of 100% in the saliva of all HIV-infected patients. A saliva collection device facilitates the sampling procedure, and if a rapid test is used, the diagnosis of infection can be established in as little as 10 min. The analysis of a group of CDC stage IV AIDS patients showed a decrease in lactoferrin (produced by the oral mucosa) in comparison with HIV-negative controls, associated with an increase in albumin (filtering from plasma), indicating an alteration of the mucosal barrier. The salivary anti-HIV-gp160 activity was largely carried by the IgG isotype whereas the salivary antibacterial activity (anti-Streptococcus sobrinus; anti-LPS from Escherichia coli) remained located in the IgA isotype as usually observed with all infectious agents. Salivary IgG carried a specific anti-gp160 activity 25-fold higher than that of serum IgG. Thus, significant local synthesis of specific IgG by oral mucosa was revealed as a characteristic of HIV infection.

Alterations in the mucosal immune system in ulcerative colitis and Crohn's disease

Emphasis is now being placed upon obtaining a better understanding of the regulatory cytokines that normally downregulate acute intestinal inflammation. These inhibitory cytokines appear to be missing or not functioning properly in patients with inflammatory bowel disease (IBD), thereby leading to perpetuation of inflammation. As we obtain an increased understanding of immune and inflammatory regulatory processes in the intestine, we will be able to devise better future therapeutic strategies for use in our IBD patients.

Validation of IgA1 and IgA2 measurements by a solid-phase immunoradiometric assay in serum and secretions

We describe specific, sensitive and reproducible immunoradiometric assays to measure total IgA and IgA subclass levels in biological fluids, which take into account the problem that polymeric forms are differently recognized in immunoassays. Sera from subjects totally deficient in one of the IgA subclasses allowed us to ensure the specificity of the subclass assays and to define the proportions of IgA1 (84%) and IgA2 (16%) in the normal pooled serum (from 30 blood donors) used as standard. With purified milk 11-S secretory IgA1 and 11-S secretory IgA2, we determined a correction factor for the corresponding polymeric forms using, respectively, monomeric IgA1 and monomeric IgA2 from pooled serum as standards. With the monoclonal antibodies used, purified 11-S secretory IgA1 was similarly recognized by both the total IgA assay and the IgA1 assay; both total IgA and IgA1 concentrations were underestimated compared with monomeric IgA or monomeric IgA1. In contrast, 11-S secretory IgA2 was better recognized by the IgA2 assay than by the total IgA assay and the values were thus overestimates. Considering this problem of recognition, we fractionated saliva and lung secretions by sucrose density gradient ultracentrifugation before measuring their IgA1 and IgA2 levels.

Immunoepidemiology of intestinal helminthic infections. 2. Immunological correlates with patterns of Trichuris infection

The significance of parasite-specific serum and secretory immunoglobulin (Ig) isotype responses as determinants of Trichuris trichiura infection intensity in endemic communities is discussed. Comparison of age-dependent isotype responses and the age profiles of infection intensity in 2 endemic communities with markedly different levels of T. trichiura transmission suggest that serum IgA responses may reflect the accumulated past experience of infection and thus may be relevant in acquired immunity to T. trichiura and contribute to the age-convexity of infection intensity in areas of intense transmission. Preliminary analysis of data from a second community-based study shows that parasite-specific secretory IgA in saliva increases with age and correlates negatively with infection intensity, suggesting that secretory IgA may also be implicated in acquired immunity to this gut-dwelling nematode.

Targeting of drugs and vaccines to the gut

Targeted delivery to the gastrointestinal tract requires a multi-disciplinary approach to research involving contributions from polymer and material scientists, gastroenterologists, pharmaceutical scientists and technologists. Intestinal delivery is important not only for drugs that act locally, but also for those with systemic activity. In particular, there is considerable interest in the oral delivery of peptides and it is felt that the colon may provide an advantageous absorption site for such molecules. The different targeting mechanisms available to the pharmaceutical scientist to provide site-specific delivery in the gastrointestinal tract will be critically assessed. Delivery systems and targeting agents, which are being developed for the delivery of drugs, may also be exploited for the delivery of vaccines, since many of the delivery problems are common to both areas. Recent developments in the design of oral antigen formulations will be discussed in this review.

Etiology of IgA nephropathy syndrome

Since Berger's original paper on mesangial IgA-IgG deposition with hematuria, there have been a number of clinical and pathological studies regarding IgA immune complexes, the mechanisms of glomerular IgA deposition leading to glomerular injury and animal models of IgA nephropathy. During the last quarter of this century, glomerular changes such as IgA nephropathy have also been observed in cases associated with other diseases, such as systemic lupus erythematosus, Schoenlein-Henoch purpura, liver cirrhosis and chronic inflammatory diseases of the lung. This evidence supports the idea of an IgA nephropathy syndrome. On the other hand, IgA is thought to be an important humoral factor at the mucosal immune system and appears to have an antibody function against various etiologic candidates of extrinsic or intrinsic substances at the mucosal and systemic immune system. Glomerular IgA deposition in IgA nephropathy syndrome is thought to result from elevated levels of circulating immune complexes or aggregated IgA due to an overproduction of polymeric IgA as antibodies in the serum and due to the clearance impairment of IgA immune complexes in the hepatic and splenic phagocytic system. The glomerular IgA subclass is not one-sided, but should be evaluated in comparison with the age of patients at renal biopsy; this indicates the approximate age of onset. Cirrhotic IgA glomerulonephritis is not related to Hepatitis B or C virus infection, but to the pathophysiologic condition of liver cirrhosis. Various etiologic candidates such as viral, microbial, dietary antigens or auto-antigens have been listed and experimental models of IgA nephropathy syndrome have provided some clues in understanding the etiology of primary IgA nephropathy. However much still remains to be clarified and some specific epitopes common among these etiologic candidates will have to be identified.

Influence of fatty acid absorption on bidirectional release of immunoglobulin A into intestinal lumen and intestinal lymph in rats

Effects of absorption of long and middle chain fatty acids on IgA secretion into the intestinal lumen and intestinal lymph and the factors which evoke changes in IgA secretion during the absorptive process were examined in rat small intestine. Bidirectional secretion of IgA from the intestinal mucosa into the intestinal lumen and intestinal lymph was continuously observed in the control condition. Perfusion of oleic acid (a long-chain fatty acid) micelle into the jejunal loop induced a significant increase in IgA output into the intestinal lymph. In contrast, lymphatic output of IgA was significantly decreased when oleic acid micelle was administered intraduodenally. Absorption of octanoic acid, a middle-chain fatty acid, did not produce any significant changes in IgA output into either direction. CR1505, a CCK-receptor antagonist, significantly attenuated the oleic acid-induced increase in IgA secretion into the intestinal lumen, but did not affect the oleic acid-induced decrease in lymphatic IgA secretion. Pluronic L-81, an inhibitor of chylomicron formation and secretion, significantly attenuated the decrease in IgA output into the intestinal lymph during oleic acid absorption without affecting the luminal IgA output. The rate of release of IgA into the intestinal lumen is stimulated by absorption of long-chain fatty acids possibly through the influence of locally released CCK, while the transport process of IgA into lymphatics is controlled by a different mechanism which is closely correlated with the intracellular formation and secretion of chylomicron.

Elevated cerebrospinal fluid IgA in humans and rats is not associated with secretory component

Immunoglobulin A (IgA) is transported across mucosal tissue membranes covalently bound to secretory component (SC). To determine if this receptor-mediated process also occurs at central nervous system (CNS) boundaries, cerebrospinal fluid (CSF) and serum from patients with CNS neuroinflammatory disease were analyzed for IgA and SC. Excess CSF IgA was detected in six of 24 patients, but no significant CSF SC was detected. In a parallel study using a rat model with normal brain barriers, inactivated lymphocytic choriomeningitis virus was microinfused into CSF. Elevated CSF IgA was detected in four of six rats, yet the proportion of secretory IgA was again insignificant compared to normal exocrine fluids (bile, semen). There does not appear to be a secretory IgA immune system at CNS boundaries and elevated CSF IgA is attributed to intrathecal synthesis.

A contemporary view of salivary research

The past 50 years of salivary research has been marked by a series of changing perceptions as new techniques and technologies have illuminated the complexities of the secretory mechanism, salivary composition, and function. The modern era began with the innovations of electrophoresis, chromatography, histochemistry, immunochemistry, electron microscopy, and microphysiology. The idea of saliva as primarily a digestive fluid composed of salts, amylase, and mucin was rapidly broadened to encompass a wide spectrum of protective proteins with the dual responsibility of protecting both hard and soft tissues. Characterization of the secretory IgA and nonimmunological antibacterial systems and the proteins responsible for the regulation of calcium and phosphate levels dominated the research in the 1960s and 1970s. An appreciation of the nature, formation, and role of the salivary pellicle and the interplay between bacterial adherence and agglutination provided a clinical thrust. Morphologists and physiologists redefined the secretory process on a molecular level. The 1980s saw the union of structure and function, both in terms of synthesis and release of the secretory products and their specific roles in the oral cavity in health and disease. The excitement of the 1990s is in the genetic control of processes and products, elucidating the mechanisms, and using the information to improve on nature: an era of great expectations and hubris. This article is essentially a personal guided tour through the past 50 years of salivary research.

Recombinant vaccine vector-induced protection of athymic, nude mice from influenza A virus infection. Analysis of protective mechanisms

Athymic, nude mice, which normally succumb to virus infection, can resolve infection with recombinant vaccinia virus (rVV) engineered to express IL-2. We have demonstrated that interferon-gamma (IFN-gamma) produced by natural killer (NK) cells and other immunocytes in response to the virus-encoded interleukin-2 (IL-2) is crucial to recovery. Here, we extend this work to show that nude mice, when primed intravenously with rVV co-expressing both IL-2 and an influenza virus haemagglutinin (HA) gene, are also protected following challenge with a lethal dose of homologous influenza virus. A substantial increase in the number of influenza virus-reactive antibody-secreting cells producing antibody of the IgM isotype, but not of the IgG or IgA isotypes, was found in spleens and lungs of the protected mice. Treatment with monoclonal antibodies to IFN-gamma or to the NK marker, as GM1, at challenge and thereafter, led to their death however, though the specific IgM antibody response was unaffected. These data suggest that both specific antibody and non-specific antiviral reactivity are important elements of the protective response and show that this immunization strategy may be used to protect severely immunocompromised individuals.

Immunoglobulin A-induced shift of Epstein-Barr virus tissue tropism

Increased immunoglobulin A (IgA) antibodies to the Epstein-Barr virus (EBV) appear months to years before the clinical onset of nasopharyngeal carcinoma and define populations at high risk for this EBV-associated epithelial cancer common in south China. In the human HT-29 epithelial cell line, polymeric IgA (pIgA) specific for EBV promoted infection of the otherwise refractory epithelial cells. When bound to pIgA, EBV entered epithelial cells through secretory component-mediated IgA transport but no longer infected B lymphocytes. Such an immune-induced shift in EBV tissue tropism provides a paradigm for endogenous spread of EBV in the immune host that predicts infectious sequelae of epithelium.

Campylobacter jejuni non-culturable coccoid cells

The behaviour of Campylobacter jejuni in the environment is poorly documented. Rapid loss of viability on culture media is reported. This phenomenon is associated with the development of so-called coccoid cells. It has been suggested that these cells can be infective to animals and man. Results obtained with ATP-measurements of coccoid cells and Direct Viable Count (DVC) support this hypothesis. Introduction of coccoid cells into simulated gastric, ileal and colon environments did not result in the presence of culturable cells. Oral administration to laboratory animals and volunteers caused no typical symptoms of campylobacteriosis. Until 30 days after uptake of the cells antibodies against C. jejuni could not be detected in the blood, and the presence of this microorganism in stool samples could not be demonstrated.