CHARACTERISTICS OF AN IMMUNE SYSTEM COMMON TO CERTAIN EXTERNAL SECRETIONS

Kinetics of anti-Campylobacter jejuni monomeric and polymeric immunoglobulin A1 and A2 responses in serum during acute enteritis

The intensity and kinetics of the serum polymeric and monomeric immunoglobulin A1 (IgA1) and IgA2 antibody responses to Campylobacter jejuni were analyzed. A rapid and marked serum IgA antibody response involving both the monomeric and polymeric components of IgA was observed after C. jejuni infections. IgA antibodies reached a peak of activity in serum during week 2 after the first symptoms of enteritis, about 10 days before the peak of IgG activity. Polymeric IgA accounted for most of the anti-C. jejuni activity at the peak of the IgA response (median, 90%; range, 44 to 98%) but rapidly disappeared from serum over a few weeks. In contrast, the serum monomeric IgA antibody response was low and was maintained over a prolonged period of time. Anti-C. jejuni IgA detected in the serum of healthy blood donors was mainly monomeric (median, 83%; range, 17 to 94%). In both the patients and the positive controls, IgA1 was the predominant (greater than 85%) subclass involved, even when the IgA antibody response was mainly polymeric. Our results suggest that polymeric IgA antibody responses are linked to a strong or persisting antigenic stimulation or both. Polymeric IgA antibodies appear to be a potential marker of acute C. jejuni infections, and their determination could provide a useful tool for the serological diagnosis of recent C. jejuni infections.

The common mucosal immune system and current strategies for induction of immune responses in external secretions

The selective induction of antibodies in external secretions is desirable for the prevention of various systemic as well as predominantly mucosa-restricted infections. An enormous surface area of mucosal membranes is protected primarily by antibodies that belong, in many species, to the IgA isotype. Such antibodies are produced locally by large numbers of IgA-containing plasma cells distributed in subepithelial spaces of mucosal membranes and in the stroma of secretory glands. In humans and in some animal species, plasma-derived IgA antibodies do not enter external secretions in significant quantities and systemically administered preformed IgA antibodies would be of little use for passive immunization. Systemic administration of microbial antigens may boost an effective S-IgA immune response only in a situation whereby an immunized individual had previously encountered the same antigen by the mucosal route. Local injection of antigen in the vicinity of secretory glands is usually accompanied by an undesirable concomitant systemic response and frequently requires the addition of adjuvants that are unacceptable for administration in humans. Immunization routes that involve ingestion or possibly inhalation of antigens lead to the induction of not only local but also generalized immune responses manifested by the parallel appearance of S-Iga antibodies to ingested or inhaled antigens in secretions of glands distant from the site of immunization. Based on extensive studies in animal models as well as in humans, convincing evidence is available that antigen-sensitized and IgA-committed precursors of plasma cells from GALT are disseminated to the gut, other mucosa-associated tissues, and exocrine glands. However, due to the limited absorption of desired antigens from the gut lumen of orally immunized individuals, repeated large doses of antigens are required for an effective S-IgA response. Novel antigen delivery systems for the stimulation of such responses are currently being examined in several laboratories. Live attenuated or genetically manipulated bacteria expressing other microbial antigens have also been used for selective colonization of gut-associated lymphoid tissues. Unique antigen packaging and the use of adjuvants suitable for oral administration hold promise for an efficient antigen delivery to critical tissues in the intestine and deserve extensive exploration. The oral immunization route appears to have many advantages over systemic immunization.(ABSTRACT TRUNCATED AT 400 WORDS)

The immunology of coeliac disease

Coeliac disease is defined as that disorder in which there is an abnormality of the small intestinal mucosa manifested by contact with the gluten of wheat and certain other cereal grains. In the immunological theory of the pathogenesis of coeliac disease, gluten, or a component, is viewed as the antigen responsible for the immune response. The search for the gluten component responsible for 'toxicity' and, by implication, antigenicity, is described. The antigen may be presented differently to the immune system by an abnormal cell membrane, either of the enterocyte, lymphocyte or macrophage. Alternatively, increased amounts of antigen may be absorbed due to increased membrane binding or permeability, either of which could be genetically determined. As a further possibility, coeliac disease may occur because the patients are immunologically hyperresponsive and this too appears to be genetically determined. The perturbations which occur in the mucosal immune system and the systemic immune system are described. It is conceivable that the major complications described (intestinal ulceration, malignancy and splenic atrophy) result from immunological disturbances. The incidence of childhood coeliac disease is declining, which may be due to altered exposure to, or increased protection from, the antigen in infancy, or to changes in environmental factors. The immunological mystery of coeliac disease continues to excite interest and fascination, and has certainly been a stimulus to our deeper understanding of gastrointestinal immunology.

Secretory IgA and serum type IgA in nasal secretion and antibody activity against the M protein

We studied IgA immunoglobulins in nasal secretions in order to clarify mucosal immunity of the nasal cavity and paranasal sinuses during chronic nasal infection. Secretory IgA and serum type IgA of 165 samples of nasal secretions were analyzed quantitatively by use of electroimmunodiffusion techniques, and the specific antibody activity of secretory IgA against the M protein of Streptococcus pyogenes was investigated by use of enzyme-linked immunosorbent assay. Results show that although the secretory IgA content in nasal secretions was elevated in chronic sinusitis, its specific antibody activity against the M protein was lower than that in normal subjects. This evidence suggests that nonspecific secretory IgA antibodies are predominantly produced in chronic sinusitis, and that mucosal immunity preventing the adherence of bacteria is impaired in the diseased mucosa.

Separation of human IgA1 and IgA2 using jacalin-agarose chromatography

A lectin isolated from the tropical jackfruit, jacalin, previously reported to precipitate human immunoglobulin A (IgA), and conjugated to agarose was used to separate the two subclasses of IgA from secretions. Jacalin-agarose binds specifically to the D-galactose moiety of IgA1 but not to IgA2 which has a different carbohydrate content and structure. IgA2 passed through the jacalin-agarose column and was collected in the void volume. IgA1 was eluted from the lectin by 0.8 M galactose. Of a representative diluted anti-alpha chain-purified colostral IgA preparation containing 50.2 micrograms IgA1 and 55.8 micrograms IgA2, 40.3 micrograms IgA1 (80.3% of the original) and 49.6 micrograms IgA2 (88.9%) was collected following jacalin-agarose chromatography. The jacalin-purified IgA1 fraction contained 8.0% IgA2 and the IgA2 fraction contained no IgA1. In addition, the IgA1 and IgA2 fractions had naturally occurring antibody activity to a normal oral bacterium. The method is easy, reproducible and specific and has many applications to mucosal immunological investigations.

Increased monomeric immunoglobulin A levels in tears from multiple sclerosis patients

Mucosal immunity and the secretory antibody are known to be important defense mechanisms against many common viruses. Tears were selected as a representative mucosal fluid, and immunoglobulin A (IgA) was examined by enzyme-linked immunosorbent assay and immunoblot. Tears from 38 normal controls and patients with systemic or ocular diseases contained almost exclusively polymeric IgA. In contrast, almost 75% of 23 patients with multiple sclerosis had detectable monomeric IgA in addition to polymeric IgA. The functional importance of this alteration in the molecular form of secretory IgA remains to be determined.

Neutrophil mediated and IgA dependent antibacterial immunity against enteropathogenic Escherichia coli in the porcine intestinal mucosa

The role of polymorphonuclear neutrophils (PMN) in the antibacterial immunity against enteropathogenic Escherichia coli (EEC) 0:149 in the porcine intestine was studied using intestinal Thiry-Vella loop (T-V loop) as a model. Intraluminal immunizations of T-V loops resulted in elevated levels of immunoglobulin A (IgA) anti-EEC 0:149 antibody in the loop secretions, an infiltration of PMN in the lumen of the loops and an increase in the concentrations of lactoferrin (LF), lysozyme (LY), cationic proteins (CP), and a specific bactericidal response in the immunized loops. PMN were observed by electron microscopy (EM) to be actively phagocytic in the lumen of the immune loops. EM observations of loop fluids as well as the abrogating effect of iron on the in vivo bactericidal response strongly suggest that the pMN played an important role in the bactericidal response in the loops against EEC. In addition to phagocytosis by PMN and subsequent intracellular killing, disintegration of PMN in the lumen of the loops and extracellular killing of EEC by the antibacterial products of PMN such as LF, LY and CP, with and/or without synergistic effect of IgA antibodies, also contribute to the bactericidal response of the immunized loops.

[Immunoglobulin A and its significance for mucosa immunity--a contribution to the understanding of microbial interactions]

The secretory immunoglobulin A is still dominating with regard to knowledges and further investigations of the causes of mucosal immunity. Origin, formation, structure and mode of action of s-IgA are extensively explored. In the clinical range results of researches on symptoms and consequences of selective IgA deficiency are gaining importance, increasingly. Patients with IgA defect suffer up to 40 times more frequently from allergies and autoimmunopathies. In the induction of the immune response cellular components of mucosa immunity attaining the Lamina propria and the epithelium with the effector cells of Peyer's patches play a particular role.

Naturally occurring IgA antibodies to ocular and oral microorganisms in tears saliva and colostrum: evidence for a common mucosal immune system and local immune response

In this study, levels of naturally occurring secretory IgA (sIgA) antibodies to bacterial isolates representative of the microflora of the human eye (Staphylococcus epidermidis and a Corynebacterium species) and the oral cavity (Streptococcus mutans serotypes c and d) were assessed in three different human external secretions. Tears and parotid saliva samples collected at the same time from 22 healthy subjects and colostrum from 11 healthy women (1-14 days post partum) were assessed for sIgA anti-bacterial antibody levels by an enzyme-linked immunosorbent assay. Significantly higher levels (P less than 0.001) of IgA antibodies to Staphylococcus epidermidis and the Corynebacterium sp. were found in tears than in parotid saliva. Furthermore, higher levels of sIgA antibodies to Streptococcus mutans serotype d occurred in parotid saliva than in tears of these subjects. Although levels of salivary sIgA antibodies to S. mutans serotype c were lower than those seen to serotype d, they were not significantly different from those in tears. However, absolute sIgA anti-serotype c antibodies per mg IgA were higher in saliva than in tears. When sIgA antibody levels to the four bacterial strains were assessed in colostrum, the proportion of sIgA antibodies per mg IgA were much lower than seen in tears or saliva. These results suggest that natural sIgA antibodies which occur in human external secretions are induced by antigen ingestion and stimulation of the common mucosal immune system. However, the local presence of antigen at a mucosal site induces greater clonal expression and results in higher levels of sIgA antibodies than at mucosal sites not exposed to local antigenic stimulation.

Phosphorylation of the rat hepatic polymeric IgA receptor

In vivo labeling with [35S]cysteine has identified three transmembrane forms of the rat hepatic polymeric IgA receptor: (i) a 105-kDa core glycosylated precursor; (ii) a terminally glycosylated 116-kDa intermediate; and (iii) a mature 120-kDa form. In the current study we show that the 120-kDa form is phosphorylated. After in vivo labeling with [32P]orthophosphate, all receptor forms were immunoprecipitated from hepatic total microsomes (TM) (with an antireceptor antiserum), separated by NaDodSO4/PAGE, and detected by autoradiography. The 120-kDa form was selectively phosphorylated, whereas the 116- and 105-kDa forms incorporated no detectable 32P. To determine the topology of the phosphorylation sites, hepatic TM isolated from rats labeled in vivo with either [35S]cysteine or [32P]orthophosphate were treated with trypsin. TM were solubilized and receptors were immunoprecipitated from lysates. With increasing trypsin concentrations, the [35S]cysteine-labeled receptor triplet was degraded to a trypsin-resistant doublet of approximately 95 and 85 kDa, indicating that approximately 20 kDa was removed from the receptor endodomain by trypsin. The same treatment removed all detectable 32P from labeled receptors. Furthermore, no 32P was detected in the 80-kDa biliary form of the receptor. Serine was identified as the only phosphorylated residue in acid hydrolysates of 32P-labeled immunoprecipitated receptor. These findings indicate that (i) the 120-kDa form is the only phosphorylated species of the receptor; and (ii) the phosphorylated residues are serine(s) located in the endodomain of the protein.

Clinical heterogeneity and reversibility of selective immunoglobulin A deficiency in 80 children

80 children with selective immunoglobulin A (IgA) deficiency--40 with severe deficiency (serum IgA less than 5 mg/dl) and 40 with partial deficiency (serum IgA greater than 5 mg/dl but less than minus 2 SD of the age-normal mean)--were followed up for 1.5 to 9 years; during which their serum and salivary IgA levels were measured periodically and the number and type of infections they had were recorded. In the partial deficiency group serum IgA rose to normal levels in half the group at a median age of 14 years and at a median time of 4 years after diagnosis, but they did not reach the normal range in the severe deficiency group. Pneumonia occurred more frequently in the severe than in the partial deficiency group. In addition, 11 of the 12 severely IgA deficient patients who had pneumonia had levels of both serum and salivary IgA of less than 0.5 mg/dl, and only 1 had detectable serum IgA levels. These data indicate that in childhood severe IgA deficiency is persistent and predisposed to pneumonia, whereas partial IgA deficiency is often transient and only occasionally associated with pneumonia.

Duct-associated lymphoid tissue (DALT) of minor salivary glands and mucosal immunity

Minor salivary glands (MSG) play a substantial role in the secretory immunoglobulin A (sIgA)-mediated immunity of the oral cavity. There are two possibilities for the induction of this immunity: (i) an explicitly local antigenic stimulus, or (ii) a remote stimulus as part of the so-called 'common mucosal immune system'. This communication is an attempt to consolidate available evidence in support of both possibilities and to address the former in detail. Although there is strong circumstantial evidence supporting the feasibility of MSG functioning as a part of the common mucosal immune system, direct experimental evidence is yet to emerge. On the other hand, there is increasing structural and physiological evidence in support of MSG serving as a local immunological organ. The purely local response is attributed to the presence of MSG duct-associated lymphoid tissue (DALT), which is comparable to gut- or bronchial-associated lymphoid tissue (GALT or BALT) in origin, tissue organization and function. DALT is accessible to oral antigens by retrograde passage through MSG ducts. Repeated topical antigenic challenging via the oral mucosa may result in the appearance of interacinar plasma cells carrying specific homologous antibodies in MSG. Gut or enteric priming of the same antigen, by passing the oral mucosa by gastric intubation, need not evoke a remote immune response in MSG. Since DALT is more likely to occur in healthy, young growing individuals, who are less likely to undergo bioptic examination of MSG, it has not yet been documented in humans. The physiologically induced DALT is apt to be confused with focal accumulations of lymphoid tissue in pathologically altered MSG, as a consequence of local and some systemic autoimmune diseases. An attempt is made to demarcaate healthy and pathological MSG on the basis of currently available clinical, serological, immunological and genetic evidence.

Secretory component: the polymeric immunoglobulin receptor. What's in it for the gastroenterologist and hepatologist?

The primary function of the SC-pIg system is to secrete pIgs into various external secretions. The cellular mechanism responsible for this transport is schematically depicted in Figure 5. Polymeric immunoglobulin A, which is synthesized by plasma cells that are part of the mucosa-associated lymphoid tissue, gains access to the SC on the abluminal surface of epithelial cells by diffusion from sites of synthesis in mucosae or enters the blood circulation and is cleared, largely by hepatic transport, into bile. The pIgA binds to SC on the abluminal surface of the epithelial cells (and probably hepatocytes) initially by noncovalent interactions that are saturable, reversible, and specific for pIgA and IgM. Subsequently, covalent interaction between SC and its ligand occurs to a variable degree in different species. The SC-IgA complex is endocytosed by the epithelial cell or hepatocyte and is transported across the cell into the external secretions by a microtubule-dependent vesicular transport mechanism. At some point during the transport, the complex is rendered soluble by proteolytic cleavage of the membrane-associated SC molecule to release the soluble sIgA into the gland lumen or the canaliculus. In the intestinal lumen, SC helps protect the sIgA molecule from proteolytic degradation. The sIgA may play a major role in the mucosal defense against pathogenic organisms or harmful antigens. The SC-pIg system differs from many of the other known receptor-ligand interactions in several important ways. First, the synthesis or expression of the receptor (SC), or both, are not regulated by the concentration of the ligand. Second, SC probably is not dissociated from its ligand or recycled to the cell surface as it is secreted in complex with its ligand (pIg) into the external secretions. Third, the interaction of pIgs with their receptor does not function to regulate an intracellular process, but results in transcellular transport of the ligand, which acts in the external environment. Fourth, after initial noncovalent, reversible binding between the receptor and its ligand, the interaction becomes covalent by the formation of disulfide linkages between SC and the pIg. Finally, SC is initially inserted into the abluminal domain of epithelial cells as an integral membrane protein and subsequently is proteolytically cleaved to a soluble molecule which is secreted by the cell. Thus, in contrast to many cell-surface receptor-ligand interactions in which the ligand is ultimately degraded and the receptor is conserved, the SC-pIgA interaction results in partial proteolytic degradation of the receptor and conservation of the ligand.(ABSTRACT TRUNCATED AT 400 WORDS)

Subclass distribution and molecular form of immunoglobulin A hemagglutinin antibodies in sera and nasal secretions after experimental secondary infection with influenza A virus in humans

Serum and nasal wash specimens from 13 human volunteers undergoing experimental secondary infection with influenza A/Peking/2/79 (H3N2) wild-type virus were examined for the molecular form and subclass distribution of immunoglobulin A (IgA) antibodies to the viral hemagglutinin (HA). Nasal IgA antibodies were polymeric and did not bind radiolabeled secretory component, indicating that they were secretory IgA antibodies. Both IgA1 and IgA2 antibodies were detected; however, IgA1 accounted for most of the rise in IgA anti-HA levels seen after infection. In serum virtually all of the IgA HA antibodies were of the IgA1 subclass. Furthermore, the serum antibodies were predominantly polymeric and were capable of binding radiolabeled secretory component. These results suggested that the serum IgA antibodies to HA were of mucosal origin and that influenza A virus HA preferentially stimulates an IgA1 response.

Effect of specific humoral immunity and some non-specific factors on resistance of volunteers to respiratory coronavirus infection

Thirty-three volunteers were inoculated intranasally with coronavirus 229 E, and their responses monitored by antibody rises, symptomatology and virus excretion. These were related to their pre-trial immune status as indicated by concentrations of specific antibodies and non-specific proteins in serum and nasal washings. Both circulating and local specific antibodies were associated with protection from infection and disease, but only specific IgA antibodies of either type appeared to shorten the period of virus shedding. Although total secretory IgA was significantly associated only with reduction of symptoms, total protein in nasal washings appeared to protect against infection also, indicating that other locally produced proteins, not identified, may be associated with resistance. Two of the many factors which may affect the concentration of circulating and local protective proteins and thus influence the outcome of virus inoculation, namely, sex of the volunteer and the interval since the previous cold, were examined. Male volunteers or volunteers who had had evidence of a recent respiratory infection were less likely to be infected, but if they were infected, they had lower clinical scores and stopped shedding virus earlier than the rest. These groups possessed higher concentrations of specific antibodies and non-specific proteins in their pre-challenge sera and/or nasal washings. The significance of these findings is discussed.

Specific IgE to food and inhalant allergens in intestinal washings of children affected by atopic eczema

Serum and rectal total and specific IgE were measured in eleven children with atopic dermatitis and eight with atopic dermatitis and associated wheezing. Specific IgE to food and inhalant allergens in rectal washings were found in fourteen patients. Of the seventy-six allergens which gave positive results, twenty were positive in both serum and intestine, thirty in serum alone and twenty-six in intestines alone. Specific intestinal IgE were confirmed by food challenge in three out of four patients whose skin-prick test and serum RAST were both negative. Local production of these antibodies was demonstrated by the 'double ratio' of Deuschl and Johansson, and the 'specific activity ratio' of Platts-Mills. Positive ratios (greater than 1) were obtained with both formulas for twelve of fourteen allergens tested. These data suggest that gut-associated lymphoid tissue may play a role in the pathogenesis of atopic disease.

Immune status in advanced upper gastrointestinal cancers

Thirty-eight cases of advanced upper gastrointestinal cancer were assessed for their immune status prior to any form of therapy. Cell-mediated immunity, as tested by absolute lymphocyte count, T-cell count and delayed cutaneous hypersensitivity reactions to purified protein derivative and phytohemagglutinin showed severe depression. Immunoglobulins A and M were elevated, while immunoglobulin G reduced. No correlation could be established between the immune status and the site of cancer or its extent, the performance status of the patients, or their response to chemotherapy.

IgA nephropathy--accumulated experience and current concepts

Primary IgA nephropathy is the most common form of glomerulonephritis in Australia. The condition presents in a variety of ways, but commonly with synpharyngitic hematuria, most often in young men in the third and fourth decades. The course of the disease is indolent but there is progression to renal failure in up to one quarter of cases. Renal biopsy morphology is variable but the essential immunofluorescence finding is diffuse mesangial IgA staining of greater intensity but often in association with other immunoglobulins. C3 is usually also present. Mesangial cellularity is increased in some two-thirds of cases, one third being of a minor focal or variable extent and one-third diffuse. Focal segmental lesions, hyaline nodules and vascular changes are frequent. Crescents are also often present. The etiology of the disease is uncertain but has been linked with HLA antigens, elevated serum IgA levels, IgA polymers, immune complexes and impaired T cell function. Secondary forms of mesangial IgA deposition occur with mucosal defects, hyperglobulinemia or impaired hepatobiliary clearance, and these may offer some insight into the immunopathogenesis of the primary disease.

Respiratory infections may reflect deficiencies in host defense mechanisms

Serious respiratory tract infections are rare in the healthy individual and most of the nuisance morbidity that occurs results from nasopharyngeal viral infections that many people get once or twice a year. The economic impact from these upper respiratory tract infections is appreciable, however, in terms of absenteeism from school or work, but unfortunately there is little that can be done to ward them off in a practical way. Pneumonia is an infrequent lifetime experience for most non-smoking adults and when it occurs, unusual circumstances may pertain--a particularly virulent microorganism is in circulation, or perhaps one has been exposed to a newly recognized germ, such as has occurred with Legionella species in the past 8 years or so. What protects us the great majority of the time is a very effective network of respiratory tract host defenses. These include many mechanical and anatomical barrier mechanisms concentrated in nose and throat; mucociliary clearance, coughing and mucosal immunoglobulins in the conducting airways and in the air-exchange region of the alveolar structures, phagocytes, opsonins, complement, surfactant and many other factors combine to clear infectious agents. The ability to mount an inflammatory response in the alveoli may represent the maximal and ultimate expression of local host defense. In some way these host defenses are combating constantly the influx of micro-organisms, usually inhaled or aspirated into the airways, that try to gain a foothold on the mucosal surface and colonize it. But many general changes in overall health such as debility, poor nutrition, metabolic derangements, bone marrow suppression and perhaps aging promote abnormal microbial colonization and undermine the body's defenses that try to cope with the situation. It is a dynamic struggle. The departure from normal respiratory health may not be obvious immediately to the patient or to the physician and repeated episodes of infection or persisting symptoms of cough, expectoration and sinus or ear infections may develop before serious assessment of the situation is taken and appropriate diagnosis gotten underway. Obvious explanations for respiratory infections may be apparent and, nowadays, side effects from antineoplastic chemotherapy or immunosuppressive therapy for a variety of diseases that create an immunocompromised host are common. In a few subjects, especially young adults who present with a cumulative history of frequent but mild infections in childhood and youth, a subtle deficiency in host defenses may exist and have been partially masked because of attentive pediatric medical care and prompt use of broad spectrum antibiotics.(ABSTRACT TRUNCATED AT 400 WORDS)

The human gastrointestinal secretory immune system in health and disease

The main function of secretory IgA is to exert immune exclusion; that is, by intimate cooperation with innate non-specific defence mechanisms, it dampens down penetration of soluble antigens and inhibits epithelial colonisation of bacteria and viruses. Secretory IgM may exert a similar protective function in the gut as its local synthesis sometimes is markedly increased, especially in selective IgA deficiency. IgG should not be considered a secretory immunoglobulin because its external translocation depends on passive intercellular diffusion. By activating complement, antibodies of this isotype may cause increased mucosal permeability and tissue damage. IgG may thus contribute to persistent immunopathology in mucosal lesions. The same is true for IgE antibodies which, in atopic individuals, may be carried into the gut mucosa by mast cells and cause their degranulation with histamine release. Secretory IgA and secretory IgM are the products of two cell types: plasma cells synthesise IgA dimers and IgM pentamers which, by non-covalent association, become complexed with the secretory component (SC) which is synthesized by serous-type glandular cells. The adsorption of the Ig polymers to the SC-expressing epithelial cells depends on J chain-determined binding sites. This fact gives biological significance to the striking J chain expression shown by mucosal immunocytes regardless of the Ig class they produce. The immunocytes populating the gut mucosa apparently belong to relatively early memory B cell clones. The obvious functional goal of J chain expression at this stage of clonal differentiation is local generation of SC-binding IgA and IgM polymers. In various gut diseases, altered immune regulation results in a disproportionately increased number of J chain-negative IgG-producing cells in the mucosa. Such altered immunological homeostasis may contribute to perpetuation of inflammatory bowel diseases.

Mechanism of neutralization of influenza virus by secretory IgA is different from that of monomeric IgA or IgG

We have found that bile is a useful source of secretory IgA (scIgA) which can specifically neutralize influenza virus infectivity. Using purified scIgA, we compared the mechanism of neutralization with that mediated by IgA monomers (prepared from scIgA by differential reduction) and IgG. At 4 degrees C, scIgA prevented the attachment of neutralized virus, while neither monomeric IgA nor IgG had any affect on this process or on the subsequent stages of infection by which virion RNA accumulates in nuclei. At 25 and 37 degrees C, scIgA permitted the attachment of approximately half the neutralized virus, but the virus was not internalized. Clearly, the neutralization depends on the character of the antibody used. scIgA may act by steric hindrance (with attachment or penetration, depending on temperature), whereas IgA and IgG neutralize infectivity at a stage subsequent to accumulation of the virus genome in the nucleus.

Enteric viral infections of calves and passive immunity

At least eight viruses have been identified, four within the last 5 yr, that produce diarrhea and pathological intestinal lesions in experimentally inoculated calves. Coronavirus and rotavirus frequently are associated with the neonatal calf diarrhea syndrome, but the etiologic role of the newly identified viruses is undefined. All diarrheal viruses replicate within small intestinal epithelial cells, resulting in variable degrees of villous atrophy. Immunity against these viral infections, therefore, must be directed toward protection of the susceptible intestinal epithelial cells. Because most of these viral infections occur in calves less than 3 wk of age, passive lactogenic immunity within the gut lumen plays an important role in protection. This report reviews methods of boosting rotavirus antibody responses in bovine mammary secretions and analyses of passive and active immunity in calves supplemented with colostrum and challenged by rotavirus. Results indicate rotavirus immunoglobulin G1 antibodies in colostrum and milk were elevated after intramuscular and intramammary vaccination of pregnant cows with an Ohio Agricultural Research and Development Center rotavirus vaccine but not after intramuscular immunization with a commercial rota-coronavirus vaccine. Feeding colostrum from intramuscular plus intramammary immunized cows to newborn calves challenged by rotavirus prevented diarrhea and shedding of rotavirus.

An immunocytochemical study on secretory mechanism of IgA in human pancreas

To analyze the secretory mechanism of immunoglobulins into pancreatic secretion, pancreatic juice IgA was measured by single radial immunodiffusion and characterized immunochemically, and immunoglobulins, J chain and secretory component (SC) were localized immunocytochemically in pancreatic tissues by the peroxidase-labeled antibody method. The concentration of IgA was 0.0225 mg/ml with a range of 0.010 to 0.049. IgA associated with SC was demonstrated immunochemically in three cases. IgA, SC and J chain were demonstrated immunocytochemically in the pancreatic duct epithelium with the features characteristic of endocytic, SC-mediated transfer of IgA. The results of the present study suggested that transfer of IgA linked by J chain and SC across ductal epithelial cells, but not acinar cells occurred in human pancreas.

Study of IgA in the cerebrospinal fluid of neurological patients with special reference to size, subclass and local production

IgA was assayed by particle counting immunoassay in cerebrospinal fluid (CSF) from non-neurological and neurological patients. Reference values had a logarithmic normal distribution with a mean of 1.54 mg/l and an upper limit of 5 mg/l. To estimate the possible intra-blood-brain barrier (BBB) production of IgA we have calculated an IgA index: CSF-IgA/serum-IgA: CSF-albumin/serum-albumin. Values higher than the upper reference limit of 0.41 were found in 12 out of 67 patients with multiple sclerosis (18%), in 5 out of 11 with aseptic meningitis, in 7 out of 8 with herpetic encephalitis, in 1 out of 8 with Guillain-Barré syndrome and in 2 cases of tuberculous meningitis. However, this index does not take into account the relative proportions of monomeric and polymeric IgA in CSF and serum. We therefore ultracentrifuged 17 paired CSF and serum samples and determined the relative proportions of monomeric and dimeric IgA and calculated the indices for monomeric and dimeric IgA. In controls the proportion of dimeric IgA in CSF was below 5% of total IgA whereas this proportion was increased up to 53.9% in the case of intra-BBB production of IgA, which is thus characterized by a very high dimeric IgA index. In all cases IgA1 remained the predominant subclass. These results had to be compared with those observed in cultures of peripheral blood lymphocytes, which secrete about equal proportions of monomeric and polymeric IgA pertaining to the IgA1 subclass.

Immunohistochemical characterization of functional markers in human minor salivary gland tumors

The distribution of carcinoembryonic antigen (CEA), secretory component (SC), immunoglobulin A (IgA), immunoglobulin M (IgM), J-chain, and lysozyme in tumors of minor salivary glands was investigated using an immunoperoxidase method. Although CEA was demonstrated in both benign and malignant tumors, its distribution was relatively more common and with increased staining intensity in malignant tissues. In pleomorphic adenomas, the distribution of SC was similar to that of IgA and J-chain, suggesting the presence of secretory IgA in the epithelial cells. However, some neoplastic epithelial cells contained SC but not IgA and J-chain. No IgM was detected in such cells. Lysozyme could be demonstrated only in pleomorphic adenomas. Mucoepidermoid tumors and adenoidcystic carcinomas were negative for lysozyme. These findings suggest that some neoplastic ductal epithelial cells of pleomorphic adenomas retain functional characteristics of normal epithelial cells.

Direct evidence for an integrated function of J chain and secretory component in epithelial transport of immunoglobulins

J chain is a polypeptide of molecular weight (Mr) approximately 15,000 common to human dimeric IgA and pentameric IgM. These immunoglobulin polymers show a high affinity for secretory component (SC) in vitro, a feature that, in some studies, has been claimed to be a function of the J chain. SC is a glycoprotein of Mr approximately 80,000 which is expressed on the basolateral surfaces of secretory epithelial cells where, according to a current hypothesis, it may act as a receptor for dimeric IgA and pentameric IgM which are selectively transported through secretory epithelial cells into exocrine fluids. Previous studies, however, have not excluded the possibility that secretory cells express isotype-specific Fc receptors for IgA and IgM which may be involved in epithelial transport. We now report that the adsorption of immunoglobulin polymers to SC-expressing epithelial cells depends solely on a J chain-determined binding site. This finding lends biological significance to the striking J-chain expression shown by immunoglobulin-producing immunocytes in secretory tissues.

Immunoglobulin levels in tears and aqueous humor of horses before and after diethylcarbamazine (DEC) therapy

A quantitative investigation of equine tear and aqueous humor immunoglobulins was done using normal horses and ponies as well as horses and ponies infected with Onchocerca cervicalis. The equine immunoglobulin isotypes IgGa, IgM, IgA and IgG(T) were quantitated by either single radial immunodiffusion (SRID) or radioimmunoassay (RIA). Tear immunoglobulin levels for IgGa (128 +/- 151 micrograms/ml), IgA (1,664 +/- 1,038 micrograms/ml) and IgM (106 +/- 74 micrograms/ml) were measured, while IgG(T) was not detectable. In horses with ocular inflammation the IgGa was 18-fold higher in the tears, 2,269 +/- 3,077 micrograms/ml. Aqueous humor obtained by paracentesis of the normal equine eye under anaesthesia, resulted in values for IgGa (45.2 +/- 20.0 micrograms/ml), IgG(T) (5.2 +/- 2.0 micrograms/ml), IgM (1.3 +/- 4.8 micrograms/ml) and IgA (0.8 +/- 1.0 micrograms/ml). A pooled sample of normal aqueous fluid obtained from over 100 horses at an equine abbatoir in Indiana gave values of 1,150 micrograms/ml for IgGa, 65 micrograms/ml for IgG(T), 2.5 micrograms/ml for IgA and 3.0 micrograms/ml for IgM. In animals infected with 0. cervicalis and treated with Diethylcarbamazine (DEC), there was a marked elevation of IgGa and IgG(T) in the tears and aqueous humor while IgA and IgG(T) were also elevated slightly in the aqueous. The findings of elevated immunoglobulin isotypes in the aqueous humor may not be related to the DEC treatment and 0. cervicalis infections but rather to repeated paracentesis and the development of acute inflammation of the equine eye as a result of the trauma of paracentesis. The elevations in equine immunoglobulin isotypes in the tears after DEC treatment are not subject to the same caveat. The preferential elevation in IgGa and IgG(T) in the tears precedes the development of corneal opacities observed in the same horses. The concentration of specific antimicrofilarial antibody in these tears remains to be determined but may well account for a major share of the total immunoglobulins detected.

Mechanisms of antibacterial immunity of mucous membranes

A survey based on both literary data and the authors own results, concerning the mechanisms of sIgA-mediated antibacterial immunity, is presented. Secretory IgA is characterized as a specific component of the immune system of mucous membranes, which can recognize harmful bacterial and distinguish them from indigenous microflora physiologically colonizing the mucous membranes, to fix them to the mucous membrane surface and to direct further factors, such as mucin, lysozyme, etc. (which form the effector component of the mucous membrane immunity system) for their final inactivation and neutralization.

Secretion of immunoglobulins and plasma proteins from the jejunal mucosa. Transport rate and origin of polymeric immunoglobulin A

Parameters of secretion of IgA and several other plasma proteins from the jejunal mucosa were investigated in 11 individuals who had a normal distribution of Ig-containing cells in the lamina propria and in one patient who was totally deficient in jejunal IgA and IgM plasmacytes. Jejunal samples were collected during segmental gut perfusion. The following results were obtained: (a) The secretion of polymeric IgA (p-IgA, mean equals 217 micrograms/40 cm per min) exceeded those of albumin (132 micrograms), IgG (35 micrograms), and monomeric IgA (m-IgA, 15 micrograms, or 6.4% of total IgA). About 35% of IgA was IgA2 in the jejunal secretion, compared with approximately 23% in serum. This closely corresponds to the 35 and 24% of IgA2 plasmocytes in jejunal mucosa and peripheral lymph nodes, respectively. (b) For each protein, a relative coefficient of excretion (RCE) was calculated (jejunum to serum concentration ratio expressed relative to that of albumin). RCEs of 1.41 for orosomucoid, 1.0 for albumin, 0.83 for IgG, and 0.74 for IgE and, in the deficient patient, of 0.64 for m-IgA and 0.016 for IgM were obtained. This was inversely related to the molecular weight of these proteins and indicated their predominantly passive transport into the jejunum. However, in normal individuals, the RCE of transferrin (approximately 1.11 greater than 1, P greater than 0.05), alpha 2-macro globulin (approximately 0.77), m-IgA (approximately 1.98), and p-IgA (approximately 218) exceeded the value expected from simple seepage from plasma, thus pointing to an additional role of either local gut synthesis and/or active transepithelial transport. (c) Approximately 98% of p-IgA, approximately 99% of IgM, and approximately 68% of m-IgA in jejunal secretions were derived from local production in the gut wall, as determined by 125I-p-IgA specific activities and/or by comparison between the RCE values of the deficient patient to the values of controls. Therefore, the jejunal production of p-IgA (approximately 312 mg/d per 40 cm vs. approximately 54 mg/d from bile) contributes the majority of upper intestinal IgA in humans. The active transport of plasma p-IgA across the intestinal mucosa (approximately 0.08 mg/40 cm per kg per d) contributes less than 2% of the total amount of p-IgA (4.5 mg/kg per d) that is cleared daily from plasma.

Immunization against influenza in humans using an oral enteric-coated killed virus vaccine

By ingestion of subunit-killed influenza virus vaccine in the form of enteric-coated capsules, local synthesis of secretory IgA (sIgA) antibody was stimulated in human nasal secretions. A fairly equal antibody response initiated by oral and intramuscular administration was demonstrated in the nasal secretions, although a systemic immune response was not elicited from ingestion of the vaccine. If the secretory antibody response resulted from absorption of antigen and transport to the respiratory mucosa, systemic (serum) antibody would be expected. Therefore these findings support the hypothesis that specialized collections of lymphoid cells in the small intestines have IgA precursor cells which circulate and populate distant mucosal sites. A number of studies have suggested that protection against mucosal infection by a variety of respiratory viruses correlates better with the presence and level of sIgA antibody than with serum antibody. The orally administered vaccine was associated with no more side effects than placebo, in contradistinction to the intramuscular route. Thus, the oral method of influenza vaccination could prove to be superior in providing for immunological protection due to equal secretory antibody stimulation, improved convenience and less toxicity.

Reaction of human colostral and early milk antibodies with oral streptococci

Colostrum or early breast milk or both from each of 16 healthy women contained agglutinating antibodies for all normal streptococcal inhabitants of the human oral cavity (S. mutans, S. sanguis, S. mitis, and S. salivarius), including those which colonize the neonatal oral cavity in significant numbers. Agglutination correlated with the amount of immunoglobulin A (IgA) binding to bacterial surfaces as measured by mixed reverse passive antiglobulin hemagglutination. Surprisingly, colostral IgA agglutinated our control organism, Brucella abortus. Low levels of colostral or milk IgM and IgG antibodies also reacted with all of the test bacteria. Absorption studies with an enzyme-linked immunosorbent assay showed that a proportion of antibodies in colostrum and early milk is specific for each of the different oral streptococci. Fractionation on Sepharose 4B indicated that 11S secretory IgA is the predominant form of colostral and milk antibody for all of the test bacteria, including B. abortus. No evidence was found that reactions other than antigen-antibody reactions resulted in binding of colostral immunoglobulins by any of the test bacteria.

Normal tear protein profiles and age-related changes

The specific and non-specific tear proteins have been analysed by means of the ELISA technique to establish the normal and age-related values. There is a linear and related decline of lysozyme and lactoferrin with age, and a similar but unrelated reduction in tear volume. IgA levels gradually decline, while caeruloplasmin and IgG both increase after the fifth decade. The results suggest that tear IgG and caeruloplasmin are probably transudates from the serum, that IgA is secreted independently of tear volume, and that lysozyme and lactoferrin are secreted at the same site but independently of tear volume.

Localization of free secretory component in pleomorphic adenomas of minor salivary gland origin

Secretory component (a glycoprotein) is an antigenically distinct portion of the secretory immunoglobulin A, which has been identified in a number of normal and neoplastic epithelial cells. Localization of secretory component was determined in pleomorphic adenomas of minor salivary gland origin using the four-step peroxidase-antiperoxidase technique. Antiserum that detected only free secretory component (FSC) was used. Staining for secretory component was noted in the epithelium that lined duct-like spaces; but was absent in myoepithelial cells and mucous acini. These findings suggest a role for FSC in evaluating the histogenesis of various salivary gland neoplasms.

Immunohistochemical distribution of immunoglobulins, lactoferrin, and lysozyme in human minor salivary glands

The immunofluorescence technique was used to examine the distribution of immunoglobulin A and its subclasses, secretory component (SC), J chain, lactoferrin and lysozyme in labial and lingual (von Ebner's) glands. IgA-containing plasma cells were found in the connective tissue around intercalated or intralobular ducts and a few were noted around acini of both glands. IgA was detected in the apical cytoplasm of intercalated and intralobular duct cells and in acini of von Ebner's glands and in demilunes of labial glands. Most IgA-containing cells also stained for J chain. The ratio of IgA1:IgA2-containing cells was approximately equal in von Ebner's and labial glands. Cytoplasmic and surface membrane-related staining for SC was detected in epithelial cells of the intercalated and intralobular ducts in both glands, in the serous acini of von Ebner's gland, and in the demilunes of labial glands. Lactoferrin was found in serous acini, demilunes, intercalated and intralobular ducts. Lysozyme was found in acinar and intercalated ducts, but was rarely seen in intralobular ducts. These results disclose the presence of cells (plasma cells and epithelial cells) and their products (IgA and secretory component) that indicate the local production of secretory IgA in minor salivary glands.

The receptor for transepithelial transport of IgA and IgM contains multiple immunoglobulin-like domains

We have cloned and sequenced cDNA for the receptor that mediates the endocytosis and transcellular transport of IgA and IgM across many glandular epithelia into external secretions. This receptor contains five extracellular domains which are strikingly homologous to each other and to immunoglobulin variable regions.

Circadian variation of secretory IgA in nasal secretions from normal subjects

In normal subjects the concentration ratio of secretory IgA (sIgA) to total IgA in nasal secretion was measured by means of enzyme-linked immunosorbent assays (ELISA). No marked circadian variation was disclosed in the sIgA/IgA ratio in nasal secretion.

Antigen processing and uptake from the intestinal tract

We have attempted, in this discussion, to summarize the processes and evidence for absorption of antigenic macromolecules in both animals and humans, comparing the infant to the adult. The mature gut retains the capacity to absorb macromolecules by an energy-dependent pinocytotic mechanism similar to that described for the transport of immunoglobulins and other enteric antigens in certain mammalian species in the neonatal state. The vast majority of adults show no ill effects as a result of this physiologic phenomenon. However, when increased (pathologic) quantities of antigenic macro-molecules gain access to the body because of a derangement in the intraluminal digestive process, or because of a defect in the mucosal barrier, both of which are present in the immature intestine, macromolecular absorption may be altered and result in either local intestinal or systemic disorders.

Immunoelectronmicroscopic study on the transport of secretory IgA in the lower respiratory tract and alveoli

To define the immunocytochemical localization of secretory component (SC), IgA and J chain in human bronchioles and alveoli, a direct peroxidase-labeled antibody method was used. SC was found in non-ciliated cells of the bronchioles including respiratory bronchioles and type II alveolar epithelial cells, whereas SC was rarely present in ciliated cells and type I alveolar epithelial cells and was absent from goblet cells. In the positively reacting cells, SC was found in secretory protein synthetic organelles such as perinuclear spaces and endoplasmic reticulum, Golgi complexes, and on the external surfaces of the apical and basolateral plasma membranes. IgA and J chain were localized in the epithelial cells where SC was found. Ultrastructually IgA was present on the apical and basolateral plasma membranes, in pinocytic invaginations of the membranes, and in vesicles distributed through the cytoplasm, especially in the apical cytoplasm of the epithelial cells where SC was found. In addition, IgA and J chain were found to be associated with the endothelial cells of the capillaries, plasma cells and the surrounding interstitium. These observations suggest that SC is synthesized and secreted by epithelial cells, especially non-ciliated cells of the bronchioles including respiratory bronchioles and type II alveolar epithelial cells. They also suggest that secretory IgA (sIgA) is transported into alveolar spaces and the bronchiolar lumen through these cells by SC-mediated transport mechanism. This sIgA may play an important role in defense mechanisms of the lower respiratory tract and alveoli.