Immunological properties and differentiation potential of human colostral lymphocytes of B cell lineage.
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Biomedical subjects
Publications and source records attributed to S J Prince.
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Healthy adult volunteers were injected either with one of two conjugates composed of Streptococcus pneumoniae type 12F polysaccharide (Pn12F) covalently coupled to diphtheria toxoid or with Pn12F alone (as a component of Pnu-Imune, a 23-valent pneumococcus vaccine). The conjugates induced Pn12F-specific antibody-secreting cells in peripheral blood with numbers and isotype distribution similar to those induced by Pnu-Imune, with immunoglobulin A (IgA) as the predominant isotype. The conjugates also elicited high numbers of diphtheria toxoid-specific antibody-secreting cells of the IgG class. There was no distinct booster effect, since a second dose of the conjugates induced antibody-secreting cells at significantly lower numbers than after the first dose. In contrast to the cell numbers, the conjugate vaccines induced higher increases of IgA1 Pn12F antibodies in serum than did Pnu-Imune. However, neither the conjugates nor Pnu-Imune induced a secretory antibody response. Antibody levels in serum and saliva correlated poorly with the frequency of antigen-specific antibody-secreting cells. Circulating antibody-secreting cells present 7 days postimmunization were probably not responsible for the high increase of antibodies in serum but rather represented a population of in vivo-activated B cells with the ability to disseminate the humoral response from the antigen recognition site to distant locations of antibody production.
The finding that ingestion of antigens results in the selection induction of IgA antibodies in external secretions suggests that antigen sensitizes Peyer's patch lymphoid cells, which migrate to mucosal sites and generate local secretory IgA (S-IgA) antibody responses. Evidence for a common mucosal immune system in humans has been scanty because of the difficulty in demonstrating migratory behavior of Peyer's patch cells. In the present study, peripheral blood mononuclear cells (PBMC) from human volunteers who had ingested capsules containing killed Streptococcus mutans were assayed for spontaneous antibody-producing cells. Four of five volunteers exhibited circulating IgA-producing cells within 7 days and reached maximum responses by days 10-12. One IgA-deficient subject exhibited IgM responses with identical kinetics. Pokeweed-mitogen-stimulated PBMC produced anti-S. mutans antibodies predominantly of the IgA isotype. Significant S-IgA anti-S. mutans antibodies were detected in saliva and tears by day 14, and the antibodies reached maximum titers by 3 weeks. No changes in serum anti-S. mutans antibodies were noted. The IgA-deficient subject produced salivary secretory IgM antibodies. These results suggest that, after antigen ingestion, peripheral blood contains antigen-specific precursors of IgA plasma cells and that their presence precedes the appearance of S-IgA antibodies in external secretions. Therefore, these experiments provide further support for the existence of a common mucosal immune system in humans.
A generalized secretory IgA response can be induced by ingestion of various antigens due to dissemination of sensitized precursors of IgA plasma cells from gut-associated lymphoid tissue to various secretory glands. Oral ingestion of a bacterial antigen by volunteers led to the parallel appearance of secretory IgA antibodies in several external secretions that was preceded by a transitory detection of IgA antibody-secreting cells in the peripheral blood. Naturally occurring secretory and serum IgA antibodies as well as secretory and serum antibodies induced by mucosal immunization belong predominantly to the IgA1 subclass; however, in external secretions IgA2 is the predominant subclass of natural antibodies to endotoxin and lipoteichoic acid. Although in external secretions specific IgA antibodies are of polymeric form, serum IgA antibodies to different antigens display considerable variability with respect to their distribution in polymeric and monomeric forms. However, after experimental infection, serum IgA antibodies to the influenza virus hemagglutinin are almost exclusively polymeric.
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Urine samples obtained from children with acute pyelonephritis and from healthy children and adults were analysed with regard to the molecular form and specific antibody activity of urinary immunoglobulins. The urinary IgA and IgG levels were quantified in unconcentrated urine by radioimmunoassay. The children with urinary tract infection had significantly higher levels of IgG and IgA than age-matched controls but not higher than healthy adults. After tenfold concentration, the urine was fractionated on an Ultrogel AcA 22 column, and the IgA, secretory IgA, and IgG in the fractions were determined by radioimmunoassay. IgA in urine from healthy adults was predominantly represented by polymeric IgA linked to secretory component; small quantities of monomeric IgA were also present. IgG eluted in the position of the serum standard. Increased proportions of IgG and monomeric IgA were found in the infected patients. Specific antibody activity of the IgG and IgA classes to antigens of the infecting Escherichia coli strain was detected in whole and in fractionated urine from children with acute pyelonephritis. The specific antibody activity in healthy adults and children was low.
The relationship between synthesis, secretion, and subcellular localization of J-chain, IgM, IgA, and IgG was investigated in cultures of PWM-stimulated human PBL and in lymphoblastoid cell lines. Cells were examined for surface, cytoplasmic, and secreted immunoglobulins (Igs) and J-chain by immunofluorescence and radioimmunoassay (RIA). By these techniques, J-chain was detected in cells that produce polymeric or monomeric Igs. In PWM-stimulated PBL the synthesis of J-chain paralleled the production of Igs. In both PWM-stimulated (for 2 days) and unstimulated PBL, equal proportions of free and disulfide-linked J-chain were found. Increased amounts of intracellular J-chain were produced at later stages in PWM-stimulated PBL and J-chain occurred mostly in a free form. In tissue culture fluids, J-chain was not secreted in a free form but was always disulfide-linked to polymeric Igs. In lymphoblastoid cell lines, J-chain was present in a disulfide-linked form in IgM and IGA producers, but in IgG cells and in an IgM cell line (DAUDI) that did not secrete IgM but expressed it on the cell membrane, intracellular J-chain was present in free form. Although various proportions of polymeric and monomeric IgA were seen in culture fluids from IgA-secreting cell lines, intracellular IgA occurred mostly in a monomeric form. Further studies revealed that the ability to produce polymers was not equally distributed among all cells and might vary according to their content of J-chain and stage of maturation. Subcellular fractionation and subsequent analyses for J-chain and Ig in PWM-stimulated PBL and in IgM or IgG-producing cell lines revealed that these proteins were associated with fractions that contained ribosomes, cell sap, and low molecular weight RNA. In lysates of IgG and J-chain producing cells grown in the presence of 3H-labeled amino acids, intracellular J-chain was not disulfide-linked to IgG.
In comparison with normal individuals, sera of patients with alcoholic cirrhosis and other liver diseases had two to four times higher levels of immunoglobulin A and three to ten time higher levels of polymeric immunoglobulin A. The possible participation of the liver in the selective removal of polymeric immunoglobulin A from serum into bile was investigated by analyzing immunoglobulin A in serum and bile specimens obtained from a group of patients with T-tube drainage of the common bile duct. Gel filtration revealed three principal fractions of biliary immunoglobulin A: secretory immunoglobulin A with J chain and secretory component; polymeric immunoglobulin A associated with J chain; and monomeric immunoglobulin A devoid of J chain and secretory component. Secretory component-complexed immunoglobulin A composed only 50% or less of the total biliary immunoglobulin A. In comparison with immunoglobulin G, polymeric forms of immunoglobulin A appeared to be selectively transported into bile whereas monomeric immunoglobulin A was not. These data suggested that the liver selectively transports polymeric immunoglobulin A from serum into bile by both secretory component-dependent and -independent mechanisms.
Human tissues were examined for their ability to produce monomeric and polymeric forms of IgA in vitro. Mononuclear cells were examined for the presence of cytoplasmic immunoglobulins and J chain (by immunofluorescence) and for the amounts and molecular forms of intracellular and secreted IgA (by radioimmunoassay). Cultured bone marrow cells were the largest producers of total IgA, and approximately 90% of the secreted IgA was monomeric. Spleen cells also produced predominantly monomeric IgA. Intestinal lamina propria cells secreted the greatest amounts of polymeric IgA, but also produced significant amounts of monomeric IgA. Tonsillar, lymph node, and peripheral blood cells produced approximately equal proportions of monomeric and polymeric IgA. These results suggested that bone marrow may be a major source of serum monomeric IgA, and that lymphoid tissues associated with secretory surfaces may provide a greater proportion of polymeric IgA than other lymphoid tissues. There was a positive correlation between the production of polymeric IgA and the presence of cytoplasmic J chain; tissues that produced predominantly monomeric IgA generally displayed fewer cells containing cytoplasmic J chain.
Colostral whey at dilutions up to 1 : 100 inhibited both the uptake of tritium-labelled thymidine and the differentiation of pokeweed mitogen-stimulated peripheral blood lymphocytes from normal adults into immunoglobulin-containing plasma cells. Upon gel filtration (Sephadex G-200), inhibitory activity was associated with high molecular weight fractions. Secretory component, but not monomeric, polymeric or colostral IgA, IgM, IgG, lactoferrin, casein or alpha-lactalbumin, inhibited the response to mitogen. Supernatants from cultures of colostral cells did not induce the differentiation of adult peripheral or cord blood lymphocytes into IgA-containing cells and did not stimulate the uptake of tritium-labelled thymidine.
Analyses of the cells present in human colostrum obtained from fifty-four healthy donors during the first four days of lactation revealed that there were 3.3 x 10(6) (range 1.1 x 10(5)--1.2 x 10(7)) cells per ml of colostrum. Based on histochemical examinations, it was found that this population consisted of 30--47% macrophages, 40--60% polymorphonuclear leucocytes, 5.2--8.9% lymphocytes, and 1.3--2.8% colostral corpuscles; epithelial cells were rarely encountered. The identity of various cell types was confirmed by Wright's stain and by a series of histochemical techniques which disclosed the presence of non-specific esterase, peroxidase, and lipids. For further characterization, the different types of cells were separated by various methods, such as Ficoll-Hypaque density centrifugation, isokinetic centrifugation on a linear Ficoll gradient, adherence to glass or plastic, and phagocytosis of carbonyl iron. Immunohistochemical staining with FITC- and/or TRITC-labelled reagents to IgA, IgM, IgG, K- and lambda-chains, secretory component, lactoferrin, and alpha-lactalbumin were applied to unseparated as well as separated colostral cells. Polymorphonuclear leucocytes (staining for peroxidase) as well as macrophages and colostral corpuscles (staining for non-specific esterase) exhibited numerous intracellular vesicles that contained lipids as well as various combinations of milk proteins. Lymphoid cells did not stain with any of these reagents and plasma cells were not detected among the colostral cells. Individual phagocytic cells contained immunoglobulins of the IgA and IgM classes, both K and lambda light chains, secretory component, lactoferrin, and alpha-lactalbumin. The coincidental appearance of these proteins in single, phagocytic cells but not in lymphoid cells indicate that the cells acquired these proteins by ingestion from the environment. Markers commonly used for the identification of B lymphocytes (surface immunoglobulins) and T lymphocytes (receptors for sheep red blood cells) were unreliable for the analysis of colostral cells (unless accompanied by subsequent morphological characterization) because strong fluorescence was observed on the surface of many non-lymphoid cells and because numerous macrophages and colostral corpuscles formed rosettes with sheep red blood cells (SRBC). Lymphocytes, often found in association with colostral macrophages or corpuscles, were classified as T cells.
Epithelial cells of human fetal intestines and of a colonic carcinoma cell line (HT-29) exhibited intracellular and surface binding of polymeric immunoglobulins of IgA and IgM classes; monomeric IgA and IgG did not bind to these cells. Secretory component was identified as the receptor involved in the immunoglobulin binding. This conclusion was confirmed by the following experiments: trypsin abrogated the surface binding of polymeric immunoglobulin, reappearance of surface secretory component (SC) restored immunoglobulin binding; the appearance of SC in developing fetal tissues coincided with their potential to bind polymeric immunoglobulin; anti-SC reagents inhibited the binding of immunoglobulins to epithelial cells; and SC-containing secretory IgA did not bind to the surface of HT-29 cells.
1) Ingestion of Streptococcus mutans antigen by human volunteers induced the selective appearance of antibodies in saliva and tears but not in serum. 2) These antibodies were associated with the IgA class as determined by enhanced or blocked agglutination, immunofluorescence and gel filtration. 3) A second series of antigen ingestion resulted in a secondary response in these secretions characterized by an earlier appearance of antibodies which reached higher titers than in the primary response.
1) SC receptors were not detected on the surface of human PBL before or after PWM stimulation or on the surface of established lymphoblastoid cell lines. 2) SC binding was detected in the cytoplasm of differentiated lymphoid cells. The majority of the SC-binding cells contained intracellular IgA. 3) The binding of polymeric IgA to the surface of human epithelial cells (colonic carcinoma HT-29) was dependent on the presence of SC. 4) These findings indicate that SC is a receptor and possible transport protein for polymeric immunoglobulins, but that it is not directly involved in the homing of the IgA precursor cells to secretory tissues.
1) Certain selective IgA-deficient subjects are capable of synthesizing functional secretory antibodies (s-IgM or s-IgA class) to indigenous oral microorganisms. 2) The presence or absence of these secretory antibodies in saliva can be correlated with the extent of caries involvement. 3) Lysozyme activity is significantly increased in saliva from immune deficient subjects though no correlation can be made with caries experience.
Ingestion of capsules which contained killed Streptococcus mutans by four healthy human subjects led to the appearance of specific antibodies in external secretions. Salivary and lacrymal antibodies were detected within 1 wk of ingestion and continued to increase throughout a 14-day immunization period, with a gradual decline during the 2 ensuing months. A second period of immunization resulted in a pronounced increase of specific antibody levels which occurred earlier than in the primary immunization period and reached peak levels by day 10. No change was detected in serum antibody levels throughout either immunization period. The antibody activity in all secretions was associated with the immunoglobulin A class, as determined by immunochemical analyses. These data indicate that ingestion of bacterial antigens selectively stimulates the immune response in secretions.