Levels Of Immunoglobulin A Antibodies Research Articles

Glucocorticoid Regulation of the Humoral Immune System. Dexamethasone Stimulation of Secretory Component in Serum, Saliva, and Bile*

Dexamethasone, a potent synthetic glucocorticoid, has been shown to increase polymeric immunoglobulin A (IgA) and antigen-specific IgA antibody levels in serum. This response coincided with a decline in IgA and IgG levels in saliva and vaginal secretions after dexamethasone treatment. To investigate the mechanism(s) of glucocorticoid action responsible for the accumulation of polymeric IgA in serum, we undertook in the present study to determine whether dexamethasone alters the production of secretory component (SC). SC is the receptor responsible for transporting IgA from blood and tissues into bile and external secretions. Dexamethasone administered in vivo increased SC levels in serum in a dose- and time-dependent manner. When bile and saliva samples were analyzed, dexamethasone treatment increased saliva SC levels and the production rate of SC by the liver, but had a pronounced inhibitory effect on both bile and salivary levels of IgA. As judged by HPLC, the majority of SC in blood was associated with polymeric IgA and not with monomeric IgA. Immunoblots showed the presence of a 29/27K doublet band of SC in serum from control- and dexamethasone-stimulated rats. These findings indicate that the elevation of polymeric IgA levels in serum after dexamethasone treatment may be due to decreased clearance of IgA into bile. Further, it demonstrates that liver production rate of SC as well as saliva and serum SC levels increase with glucocorticoid treatment. This findings suggests that glucocorticoids, which are known to stimulate hepatocyte SC synthesis in vitro, increase SC levels in blood, possibly as SC fragments that are capable of binding polymeric IgA and retarding its clearance from blood to bile.

Immunoglobulin A and immunoglobulin G antibody responses to alginates from Pseudomonas aeruginosa in patients with cystic fibrosis

Patients with cystic fibrosis have a high prevalence of mucoid, alginate-producing Pseudomonas aeruginosa that causes chronic infection of the mucosal surface of the lungs. We developed enzyme-linked immunosorbent assays (ELISAs) for determination in serum of immunoglobulin A (IgA) and IgG antibodies to alginate purified from P. aeruginosa and an ELISA for detection of IgA antibodies to a polyvalent P. aeruginosa standard antigen. Absorption experiments indicated that the assays were antigen and antibody specific and had analytical variations that ranged from 7 to 19%. Serum samples from 207 patients with cystic fibrosis, 100 healthy children, and 94 healthy adults were examined. The patients responded to P. aeruginosa infection with early IgA and IgG antibody responses that were significantly higher than in controls and noncolonized patients. Analysis of paired serum samples showed that infected patients had an increase in specific IgG and IgA antibodies that was significantly higher than in noncolonized patients. The serological data were analyzed for correlation with clinical condition; poor lung function was significantly associated with increased levels of IgA and IgG antibodies to P. aeruginosa alginate and to the standard antigen and with a relative excess of IgA antibodies to the standard antigen compared with IgA antibodies to P. aeruginosa alginate. The assays showed high predictive values if positive, but a negative test did not exclude infection, and the ELISAs should not be used for diagnostic purposes. Mucoid strains were present initially in the sputa of 28 of 54 infected patients with paired serum samples. These patients had a significant increase in anti-alginate antibodies, but it was not different from the increase seen in patients infected only with nonmucoid strains. Therefore, alginate may also be produced in vivo by nonmucoid P. aeruginosa. The study showed that early formation of IgA and IgG antibodies to P. aeruginosa alginate did not prevent development of chronic infection and that P. aeruginosa-specific IgA antibodies correlate with poor lung function.

NON-SPECIFIC MESANGIAL STAINING WITH ANTIBODIES AGAINST CYTOMEGALOVIRUS IN IMMUNOGLOBULIN-A NEPHROPATHY

The glomerular staining of a commercial polyclonal antiserum against cytomegalovirus (CMV) and of a mixture of 13 monoclonal anti-CMV antibodies in twelve patients with immunoglobulin-A (IgA) nephropathy was examined. The polyclonal antiserum stained the mesangium in all patients. The CMV staining coincided only partially with that of IgA in five patients and the staining distributions were discordant in six. The monoclonal antibodies stained mesangium in only one patient. Serum levels of IgA and IgG anti-CMV antibodies did not differ between patients and controls. In western blot analysis, the polyclonal antiserum reacted with three proteins in uninfected human fibroblasts. Absorption of the antiserum with uninfected fibroblasts reduced the reactivity on western blot analysis and eliminated glomerular staining in five of six renal biopsy samples. It is concluded that the previously reported binding of anti-CMV antibodies to glomeruli from patients with IgA nephropathy may be the result of contaminating antibodies to human antigens.

Effective immunity to dental caries: enhancement of salivary anti-Streptococcus mutans antibody responses with oral adjuvants.

In the present study, we compared the ability of the soluble adjuvants concanavalin A (ConA), muramyl dipeptide (MDP), and peptidoglycan (PG) to enhance immune responses to orally administered particulate antigens of Streptococcus mutans 6715 in gnotobiotic rats. The isotype and levels of antibody in saliva and in serum from experimental rats were determined by an enzyme-linked immunosorbent assay using S. mutans whole cells (WC) as the coating antigen. The specificities of salivary and serum immunoglobulin A (IgA) antibodies to particulate S. mutans antigens, lipoteichoic acid, S. mutans serotype g carbohydrate, and dextran were also determined. When 50 micrograms of ConA was used as the oral adjuvant with S. mutans 6715 WC immunogen, a slight enhancement of immune responses was obtained. A higher dose of ConA suppressed humoral responses to the immunogen. Enhanced immune responses, especially of the IgA isotype, in both serum and saliva were induced in gnotobiotic rats given MDP and either S. mutans 6715 WC or purified cell walls (CW) by gastric intubation. Elevated IgA antibody levels to CW, lipoteichoic acid, and carbohydrate were observed in rats given S. mutans WC and MDP by gastric intubation, whereas oral immunization with S. mutans CW and MDP resulted in higher antibody levels to CW and carbohydrate and lower levels to lipoteichoic acid when compared with the antibody levels in rats given antigen alone. Rats orally immunized with either S. mutans WC or CW and MDP and challenged with virulent S. mutans 6715 exhibited significantly (P less than or equal to 0.05) lower plaque scores, numbers of viable S. mutans in plaque, and caries scores than did rats immunized with antigen alone or in infected-only controls. In another series of experiments, a PG fraction derived from S. mutans 6715 CW was assessed for adjuvant properties. The oral administration of PG and either S. mutans WC or CW induced good salivary and serum IgA antibody responses. The specificity of the antibodies was similar to that obtained in rats given antigen and MDP. Rats receiving either S. mutans WC or CW and PG and challenged with virulent S. mutans 6715 had lower plaque scores, fewer numbers of viable S. mutans in plaque, and lower caries activity than did infected rats receiving S. mutans WC or CW immunogen alone. These results provide evidence that soluble adjuvants derived from the gram-positive bacterial CW, e.g., MDP and PG, are effective oral adjuvants and augment IgA immune responses to particulate S. mutans antigens which are protective against the mucosally associated disease, dental caries.

Effect of neonatal thymectomy on immune responses of rats to Streptococcus mutans.

The effect of neonatal thymectomy on secretory and systemic antibody responses in rats was studied. Groups of normal or thymectomized (Tx) rats were infected or immunized and infected with Streptococcus mutans 6715. Tx rats exhibited a significantly lower level of salivary immunoglobulin A (IgA) antibody to S. mutans after a 45- to 65-day infection. Similarly, after multiple local injections of formalinized S. mutans, Tx rats showed a delay in the appearance and lower levels of salivary IgA antibody to S. mutans. Serum IgG antibody levels were also decreased in Tx rats with both experimental protocols. In contrast, salivary IgG and serum IgM anti-S. mutans activity in Tx and normal rats were similar during the experiments. These results demonstrated that thymus deprivation at birth produces profound effects on the ability of rats to manifest secretory IgA antibody responses to the pathogenic microorganism S. mutans.

Immunoglobulin A antibody levels in human tears, saliva, and serum.

The presence and level of immunoglobulin A (IgA) antibodies to the oral microorganism Streptococcus mutans were determined in human tears, parotid saliva, and serum by a modified, indirect enzyme-linked immunosorbent assay. IgA antibodies were found in the tears of all 15 subjects, although S. mutans is a nonocular bacterium. The IgA antibody levels in tears and saliva were not significantly different. This finding suggests that the level of IgA antibody activity per volume is independent of the naturally occurring site of the antigen, and that local stimulation does not cause a significant difference in the antibody level per volume of secretion between exocrine sites. Much higher levels of IgA antibody were present in serum, suggesting that after oral ingestion of antigen both the systemic and exocrine systems are stimulated. IgG antibodies to S. mutans were also found in human tears, saliva, and serum. No relationship between serum levels and tear and saliva levels was found for either IgA or IgG antibodies. Thus the antibodies in tears and saliva did not appear to have leaked from serum. We conclude that there may be remote regulation of both the ocular and the parotid IgA and IgG antibody systems.

Virulence-related physiological changes and antigenic variation in populations of Streptococcus mutans colonizing gnotobiotic rats.

The purpose of this study was to determine if populations of Streptococcus mutans which were undergoing antigenic variation while colonizing gnotobiotic rats concomitantly became altered in physiological characteristics which affected their virulence. S. mutans strain JBP (serotype c), which was freshly isolated from a carious lesion in a 6-year old child, was used to inoculate gnotobiotic rats; uninfected animals served as controls. Substrains were isolated from animals 1, 2, 3, 4, and 12 weeks after infection; samples of pilocarpine-stimulated saliva were also obtained from representative animals for antibody analyses. Isolates derived from stock cultures of strain JBP proved to be homogeneous with respect to all of the physiological characteristics monitored. However, substrains isolated from the animals within 4 weeks after infection were altered with respect to their ability to agglutinate in the presence of sucrose, their ability to form adherent growth in sucrose broth, and the terminal pH attained in glucose broth. Some isolates obtained 12 weeks after infection no longer synthesized detectable levels of c antigen or intracellular glycogen, and they formed atypical smooth colonies on mitis salivarius agar. With an enzyme-linked immunosorbent assay, low levels of immunoglobulin A (IgA) antibodies reactive with whole JBP cells were detected in saliva samples of uninfected control animals at each sampling period; these evidently were induced to antigens contained in the diet of the animals. Significantly higher levels of IgA antibodies were present in saliva samples from animals infected with strain JBP for 3 weeks or longer. Thus, the emergence of antigenic and physiological variants of S. mutans in the animals was paralleled by increased levels of salivary IgA antibodies. The reactivity of salivary IgG with JBP cells was low, and it fluctuated in both groups of animals. No antibodies of the IgM class were detected. When tested in gnotobiotic rats, several variants, including strains which no longer formed typical rough colonies or adherent growth in sucrose broth, proved much less virulent than parental strain JBP in inducing carious lesions. Prior oral immunization, which resulted in higher levels of salivary and serum IgA antibodies reactive with strain JBP, was found to accelerate the emergence of smooth-colony variants in the animals; it was also associated with decreased streptococcal population levels on the teeth and in feces of the rats. It is suggested that part of the mechanism by which artificial immunization leads to a reduction in dental caries development in experimental animals is due to the earlier selection of less virulent streptococcal populations.

Human antibodies to immunoglobulin A (IgA). a radioimmunological method for differentiation between anti-IgA antibodies and IgA in the serum of IgA deficient individuals

In the sera of 12 out of 27 individuals with IgA deficiency (serum level below 0.02 mg IgA/ml) class-specific anti-IgA antibodies were demonstrated by haemagglutination. These sera showed false-positive results in a solid-phase inhibition radioimmunoassay (RIST) (apparent IgA concentration between 0.6 and 13.7 μg IgA/ml) indicating that the RIST is not an appropriate test for the analysis of serum of IgA deficient individuals. A modification of the RIST is proposed (titration RIA) that permits differentiation between low levels of IgA and class-specific anti-IgA antibodies. With this test IgA deficient individuals could be classified as those with low but detectable levels of IgA and those with class-specific anti-IgA antibodies. A computer procedure was developed to calculate both the amount and the avidity (K) of the anti-IgA antibodies and to simulate the assay system. The K value calculated from experimental points proved to be an overestimation of the K value which fitted most adequately in the simulation. The comparison of the results with clinical findings indicated a possible correlation between the amount and the avidity of the anti-IgA anti-bodies and the appearance of anaphylactic reactions after transfusion of IgA.

The proteins in nasal secretion. II. A longitudinal study of IgA and neutralizing antibody levels in nasal washings from men infected with influenza virus.

Following influenza virus infection, virus-neutralizing antibody was detected earlier, rose to high titers sooner, and was demonstrable more frequently in nasal washings from men who had had relatively high concentrations of immunoglobulin A (IgA) in their nasal washings prior to the infection. Four men who had relatively low levels of nasal IgA before inoculation were the only ones who experienced typical febrile influenza. Virus-neutralizing antibody was detected relatively late and infrequently in the postinoculation nasal washings from these men. These findings suggest that the immunologic response to influenza virus at the mucous membrane surface may play a role in limiting infection, and thereby avert clinical illness.