Virus-specific polymeric immunoglobulin A antibodies in serum from patients with rubella, measles, varicella, and herpes zoster virus infections.

More than 85% of the immunoglobulin A (IgA) antibodies in normal adult serum are monomeric (m-IgA). By contrast, virus-specific IgA is mainly polymeric (p-IgA) in sera from patients with rubella, measles, and varicella. Specific m-IgA antibodies only reach quantitative significance in late convalescence. In patients with herpes zoster, on the other hand, a varying response was observed: in three of six sera, specific IgA was absent or at a very low titer, whereas in the remaining three cases, a high titer of both p-IgA and m-IgA was noted. These results suggest that in the initial response to rubella, measles, and varicella-zoster viruses, specific IgA first appears as p-IgA and only later becomes, or is replaced by, m-IgA.     

Rat C3 Conversion by Rat Anti-2,4, Dinitrophenyl (DNP) Hapten IgA Immune Precipitates

Monomeric (m-) and polymeric (p-) anti-DNP monoclonal (MC) rat IgA antibodies (Ab) were tested for precipitation with DNP-bovine serum albumin (DNP-BSA) and C3 conversion in rat serum, with rat MC anti-DNP IgG2b used as reference. At equivalence, p-IgA rapidly precipitated DNP-BSA, with little antigen (Ag) left in the supernatant. In contrast, m-IgA at five-fold higher concentration precipitated Ag very slowly, with less than 50% of Ag precipitated at equivalence. The Ag/Ab weight ratio at equivalence was 0.13 for both m- and p-IgA, but the molar ratio was 0.3 for m-IgA and close to 1.0 for p-IgA, suggesting a higher avidity of p-IgA. Rat C3 conversion by rat IgA immune precipitates (IP) was about 20% with m-IgA and 40% with p-IgA. EGTA did not significantly affect these figures. Therefore, rat MC IgA IP activated the rat alternative C pathway. Neither rat nor mouse IgA anti-DNP IP activated C3 in normal human serum.     

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.     

Complement-mediated solubilization of rat IgA immune precipitates

The complement-mediated solubilization (CMS) of immunoprecipitates (IP) consisting of DNP-rat serum albumin (RSA) and rat monoclonal anti-DNP antibodies of the IgA [both polymeric (p-) and monomeric (m-)] or IgG2b (sub)class was studied. In contrast to IgG2b IP, solubilization of IgA IP was only observed in an autologous system, with rat serum as the source of complement. IP prepared using m-IgA were solubilized faster than those prepared using p-IgA. Analysis of both affinity and avidity of the antibodies, indicated that this difference may be due to the lower avidity of the m-IgA antibodies as compared to p-IgA. Analysis of the solubilized IP revealed deposition of C3 and C4 on IgG2b, and only C3 on IgA IP. These results point toward a role of the alternative pathway in the solubilization of IgA IP. Size analysis of the solubilized IgA IP employing sucrose density gradient ultracentrifugation, indicated that these were heterogeneous, with a size generally larger than 19 S.     

Rat polymeric IgA binds C1q, but does not activate C1

Immune complexes, prepared with monoclonal rat IgA antibodies directed against DNP, activate the alternative pathway of the complement system in rat serum. In this study, the interaction of these monoclonal IgA antibodies with the classical pathway of complement was investigated. Monoclonal polymeric IgA (p-IgA) was shown to inhibit the IgG2b-mediated classical pathway-dependent lysis of TNP-coated sheep red blood cells. In addition, the binding of C3 to solid phase IgG2b immune complexes was inhibited by p-IgA. Monoclonal monomeric IgA (m-IgA) was much less efficient in this respect. To further analyse the effect of p-IgA on the activation of the classical pathway by IgG2b immune complexes, the interaction of p-IgA with C1 was studied. It was found that p-IgA antibodies bind C1q. No species-specificity was observed, since both rat and human C1q were bound. Whereas binding of C1q in C1 to IgG2b resulted in activation of C1, binding to p-IgA did not. The binding of C1q to both p-IgA and IgG2b could be inhibited by monoclonal antibodies directed against the globular heads of C1q, but not by monoclonal antibodies directed against the collagen tail. The formation of insoluble p-IgA immune complexes was inhibited in the presence of rat serum or C1. These studies indicate that C1q binds to p-IgA by its globular heads, and thereby may modulate classical pathway-mediated reactions such as the inhibition of immune precipitate formation.     

In vivo activation of complement by IgA in a rat model.

In this study we investigated the capacity of rat IgA to activate complement (C) in vivo in a rat model. Rat monomeric (m-), dimeric (d-) and polymeric (p-) IgA MoAbs were injected intravenously and assessed for deposition of C3 and C4 on IgA. By ELISA it was shown that both d- and p-IgA bound C3 whereas no binding of C3 by m-IgA was observed. Polymeric IgA was more efficient in binding of C3 as compared with d-IgA. However, in haemolytic assays no consistent decrease of plasma complement levels was observed except for dimeric IgA which induced a marginal consumption of AP50. When rats were pre-treated with cobra venom factor (CVF) to deplete C3, no C3 deposition was found on m-, d- or p-IgA. Neither m- nor d- or p-IgA was able to bind C4 in vivo. In agreement with the results described above, large sized polymeric IgA was shown to be taken up by Kupffer cells (KC) together with C3. No C3 was detected when rats were depleted of C using CVF. Taken together, the experimental data suggest that d- and p-IgA are able to activate C via the alternative pathway in vivo.     

Measurement of total, monomeric and polymeric IgA in human faeces by electroimmunodiffusion.

Total (t), monomeric (m) and polymeric (p) immunoglobulin A (IgA) levels were simultaneously measured in mixed faecal material collected over three consecutive days using a modified one-dimensional immunoelectrophoretic assay, which is a precise and reproducible method. Faecal t-, m- and p-IgA levels were statistically higher in 32 diarrhoeic patients than in a group of 16 healthy subjects (respectively 2.2, 2.6 and 2.0 times the normal). The values were also significantly different (P less than 0.001) when results were expressed as output per day in order to estimate the secreting capacity of gut. Moreover, the m-IgA/t-IgA percentages were significantly higher in faeces from diarrhoeic patients (42.3%) than in normal faeces (26.5%). These results confirm the importance of faecal IgA determination in estimating the local production of the IgA in various gastrointestinal tract disorders.     

Activation of rat complement by soluble and insoluble rat IgA immune complexes

The ability of rat monoclonal IgA, specific for 2,4-dinitrophenyl (DNA), to activate the complement (C) system of the rat was investigated using aggregated IgA or IgA immune complexes (IC). IgA was coated onto a solid phase, and tested for its capacity to bind C3 upon incubation at 37 degrees C in normal rat serum (NRS) in the presence of Mg-EGTA. Binding of C3 was observed dependent on the dose of dimeric (d-), polymeric (p-) and secretory IgA tested. In contrast, little C3 fixation was observed in this system with monomeric (m-) rat IgA or with mouse m- and d-IgA (MOPC315). Soluble and insoluble rat IgA IC were prepared using dinitrophenylated rat serum albumin (DNP8RSA) as antigen (Ag), and assessed for C activation. It was shown that insoluble IC (immune precipitates; IP) containing m-, d- or pIgA of rat origin activate the alternative pathway of rat C, as demonstrated by their capacity to induce C consumption in NRS in the presence of Mg-EGTA. When p- and m-IgA IP were compared for their capacity to activate C, it was found that p-IgA activated C four times as efficiently as m-IgA IP (at 2 mg/ml). Soluble rat IgA IC were prepared in an excess of DNP8RSA, fractionated by gel filtration on Sepharose 6B, and analyzed for C activation and antibody (Ab)/Ag ratio. In contrast to m-IgA IP, soluble m-IgA did not activate C. On the other hand soluble d-IgA IC activated C dependent on their concentration and size: at a concentration of 0.1 mg/ml high-molecular weight d-IgA IC with a high Ab/Ag ratio were four times as efficient as low-molecular weight IC with a low Ab/Ag ratio, and twice as efficient as IP prepared at equivalence. To demonstrate the induction by IgA of the assembly of the terminal membrane attack complex, trinitrophenyl (TNP)-conjugated rat red blood cells (TNP-RRBC) coated with d- or p-IgA were shown to be lysed in NRS in the presence of Mg-EGTA. No lysis of m-IgA-coated TNP-RRBC was observed. The results in this study demonstrate that both soluble and insoluble rat IgA IC activate the alternative pathway of homologous rat C. Alternative pathway activation by soluble rate IgA IC is dependent on the size of the IC. The degree of polymerization of the IgA Ab itself also influences C activation.     

An acute model for IgA-mediated glomerular inflammation in rats induced by monoclonal polymeric rat IgA antibodies.

An acute model for IgA-mediated glomerular inflammation in rats was induced by the in situ deposition of IgA directly into the glomerular mesangium. F(ab')2 anti-Thy1 MoAb was used to anchor an antigen, DNP (2,4-dinitrophenol), in the glomeruli of rats. Subsequent infusion of rat polymeric (p-) or monomeric (m-) IgA MoAb with specificity for DNP resulted in mesangial deposition of IgA in both groups of rats. However, acute proteinuria was observed only in p-IgA-treated rats and not in PBS- or m-IgA-treated rats. Immunofluorescence analysis revealed deposition of C3 in an identical pattern to that of IgA in the glomeruli of p-IgA-treated rats. No mesangial deposits of C4 or C1q were seen in these animals. Rats receiving m-IgA or PBS displayed no detectable C3, C4 or C1q deposition. The amount of proteinuria in p-IgA-treated rats was related to the amount of deposited C3. The presence of intraglomerular monocytes was only observed 2 days after p-IgA injection. By light microscopy, aneurysm formation, mesangial hypercellularity and matrix expansion were seen only in p-IgA-treated rats. However, by 37 days post-injection complete resolution of the lesions was observed. No histological renal changes were observed in PBS- or m-IgA-treated rats. In conclusion, an acute form of IgA-mediated nephritis in rats was induced by p-IgA but not by m-IgA. This reproducible model provides a basis for further study into the mechanisms of IgA-mediated glomerular inflammation.     

Urinary IgA in IgA nephropathy and Henoch-Schoenlein purpura

To determine the concentrations and molecular forms of urinary IgA in IgA nephropathy and Henoch-Schoenlein purpura, we studied 29 patients with these IgA-associated renal diseases (IgAN). Control groups comprised 10 patients with other diverse renal diseases and 11 healthy volunteers. Urinary IgA and IgG concentrations were higher in IgAN than in either control group and correlated positively with the serum creatinine concentration as well as the urinary protein excretion (P<0.01). However, IgA/IgG ratios did not differ among the three groups. Polymeric IgA (p-IgA) in the urine predominated only in normals; in IgAN and patients with other renal diseases, monomeric IgA (m-IgA) occurred almost exclusively. Serum IgA concentrations were generally normal in IgAN; four patients had concentrations greater than 500 mg/dl. Although the fraction of p-IgA in serum (median, 18%) was increased above normal (5–10%) in 13 of 16 (81%) subjects, neither the concentration of IgA or IgG nor the amount of p-IgA correlated with the serum creatinine concentration. These data suggest that the molecular form and concentration of urinary IgA are not discriminating for IgAN and are independent of these characteristics of serum IgA.     

Secretion of immunoglobulins and plasma proteins from the colonic mucosa: an in vivo study in man.

There are no available data on immunoglobulins and albumin outputs into the normal human colon. We thus measured the intracolonic secretion rates of IgA, IgG, IgM, secretory component (SC) and plasma proteins (albumin (Alb), orosomucoid (Oro), transferrin (Transf) and alpha 2-macroglobulin (alpha 2-M)). Using a pancolonic perfusion technique in 10 healthy volunteers (six females, four males, mean age 24 years), concentrations and outputs of Alb, immunoglobulins, SC, Oro, Transf and alpha 2-M were measured in the rectal effluents by immunoradiometric assay. Monomeric (m) and polymeric (p) IgA distribution was analysed by sucrose density ultracentrifugation. The secretion of polymeric IgA (p-IgA) was 153 micrograms/min, i.e. 220 mg/day, exceeding that of other immunoglobulins (m-IgA 8.5 micrograms/min; IgG 33.5 micrograms/min; IgM 17 micrograms/min) and of non-immunoglobulin proteins (Alb 104 micrograms/min; Oro 9 micrograms/min; Transf 7 micrograms/min; alpha 2-M 4.5 micrograms/min). p-IgA was entirely linked to SC (secretory IgA) and 12% of SC was in free form. About 62% of total IgA was IgA2. For each protein, a relative coefficient of excretion (RCE) was calculated (colon to serum concentration ratio expressed relative to that of Alb). The p-IgA, IgM and m-IgA RCE were 277, 6 and 2.2 times higher than the values predicted from their molecular weight. RCE of non-immunoglobulin proteins also exceeded the values expected from a passive seepage from the vascular compartment. The intracolonic clearance of Alb extrapolated to 24 h was only 3.7 ml/day. These results show the high local production and/or the facilitated transport to the colonic lumen of p-IgA, and are in very good agreement with the distribution of plasma cells in the colonic mucosa.     

Polymeric and Monomeric IgA Response in Serum and Milk after Parenteral Cholera and Oral Typhoid Vaccination

The effect of vaccinating lactating Pakistani mothers with a combination of live oral typhoid vaccine and parenteral inactivated cholera vaccine on specific milk and serum IgA antibodies in both monomeric (m) and polymeric (p) forms was analysed. IgA antibody titres peaked for both antigenic specificities 2 weeks after the first dose of vaccine. 82 +/- 7% of anti-Vibrio cholerae and 72 +/- 17% of anti-Salmonella typhi IgA were in the polymeric form. These serum pIgA antibodies were mainly dimeric IgA, not complexed with the secretory component. They disappeared more rapidly from serum than mIgA antibodies. Anti-V. cholerae IgA responses were parallel in serum and milk samples, whereas anti-S. typhi responses were dissociated. In milk, IgA antibodies were secretory IgA for both antigenic specificities, being probably of local origin in the mammary gland. Our results indicate that both oral and parenteral vaccinations can induce pIgA antibodies in serum and secretions, confirming that the presence of pIgA in serum does not necessarily reflect an immune stimulation only at the mucosal level.     

Induction of Salivary Antibody Responses in Rats after Immunization in Peyer''s Patches

We examined salivary, milk, and serum antibody levels after immunization in the Peyer's patches (Pp) of rats with horse spleen ferritin. Priming of the Pp one day after parturition led to the appearance of IgG, but not IgA or IgM, anti-ferritin antibodies in saliva 9 days later. IgG and IgM antibodies were detected both in milk and in serum, whereas IgA antibodies could only be demonstrated in milk. During a second lactation period the salivary antibodies had vanished but IgG antibodies could still be detected in milk and serum. During a third lactation period, when the rats were immunized in the Pp a second time, not only IgG but also IgA anti-ferritin antibodies appeared in the saliva. Salivary IgG antibody levels and milk IgG, IgM, and IgA antibody levels were higher than those observed after primary immunization in the Pp. The IgG antibody activity in the saliva was positively correlated to the serum IgG antibody activity. It is concluded that salivary IgA antibody responses can be induced by immunization in the Pp. The results of this study suggests that IgA antibodies detected in saliva are produced locally by cells that have migrated from the intestinal lymphoid tissue to the salivary glands.     

Optimizing oral vaccines: induction of systemic and mucosal B-cell and antibody responses to tetanus toxoid by use of cholera toxin as an adjuvant.

Cholera toxin (CT) is an effective mucosal antigen and acts as an adjuvant when given orally with various antigens; however, few studies have compared the levels of antibody responses to CT and coadministered protein in systemic and mucosal tissues. In this study, we used tetanus toxoid (TT) for assessment of immune responses. Time course and dose-response studies established that 250 micrograms of TT given orally with 10 micrograms of CT three times at weekly intervals induced high serum and gastrointestinal tract anti-TT and anti-CT antibody responses. Oral immunization with TT alone induced no detectable mucosal immunoglobulin A (IgA) antibodies in fecal extracts and only weak serum IgG anti-TT responses. The coadministration of CT and TT induced peak serum IgG anti-TT responses following two oral doses that remained constant after the third oral immunization, while optimal mucosal IgA responses were seen after the third oral immunization. The serum anti-TT response obtained with CT and TT proved protective against TT challenge (100 minimum lethal doses), whereas mice orally given CT or TT alone died. Antigen-specific B-cell responses were assessed with an isotype-specific Elispot assay of isolated lymphoid cells from the spleen, Peyer's patches, and the small intestinal lamina propria. Interestingly, approximately fourfold-higher numbers of IgA anti-CT than of anti-TT antibody-producing (spot-forming) cells occurred in lymphocytes from the lamina propria of mice orally immunized with both TT and CT. The adjuvant CT did not induce polyclonal B-cell responses in mice given CT by the oral route, since no significant differences in total numbers of B cells producing IgA, IgG, or IgM were found compared with the numbers in mice given TT alone. The results clearly indicate that serum and mucosal antibody responses develop with different kinetics and that protective TT-specific antibody responses are generated in the systemic compartment when TT is administered with CT via the oral route.     

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

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

Subclass and molecular form of immunoglobulin A antibodies to Actinobacillus actinomycetemcomitans in juvenile periodontitis

Patients with juvenile periodontitis frequently have elevated levels of serum immunoglobulin A (IgA) antibodies to antigens of Actinobacillus actinomycetemcomitans. IgA occurs in two subclasses, IgA1 and IgA2, and in monomeric and polymeric forms. Because IgA1 is susceptible to cleavage by IgA1 proteases produced by microorganisms found at mucosal sites and in the gingival crevice, we wished to determine the IgA subclass distribution of antibodies to antigens of A. actinomycetemcomitans. The molecular form was examined because it may indicate the origin of the IgA and because the form differs in acute and chronic infections. There is also evidence that monomeric and polymeric IgA have different biological functions. Serum was taken from patients with juvenile periodontitis before and at intervals during and after initiation of therapy. IgA subclass distribution was determined against a sonic extracts of A. actinomycetemcomitans ATCC 2952a (serotype b) by using monoclonal anti-subclass reagents in an enzyme-linked immunosorbent assay. To determine the molecular form of the antibodies, sera were separated by high-performance liquid chromatography on a size-exclusion column. Fractions were assayed for antibody activity by the enzyme-linked immunosorbent assay, and described above. The results of the subclass analysis of the sera indicated that while both IgA1 and IgA2 antibodies to A. actinomycetemcomitans sonic extract are often found before, during, and after treatment, IgA1 antibodies dominated the response. There was a predominance of monomeric IgA1 antibodies to A. actinomycetemcomitans sonic extracts in most samples before, during, and after treatment. The monomeric form is consistent with what is seen in other chronic infections. The predominance of IgA1 antibodies implies that any protective effects of the IgA response to A. actinomycetemcomitans could be compromised by microbial IgA1 proteases.     

Salivary and serum antibodies in patients with Yersinia enterocolitica infection

The systemic and secretory antibody response in patients with yersiniosis was studied by measuring Yersinia antibodies of various isotypes (IgG, IgA and IgM) and the total concentrations of the corresponding Ig classes in serum and saliva. Specific antibody activities of IgG (IgG antibody concentration divided by IgG concentration) were almost identical in serum and saliva of all patients although the pair of values varied from patient to patient. Almost all salivary IgG of these patients was therefore probably a transudate from the blood. Specific antibody activities of IgA and of IgM, on the other hand, varied independently in serum and saliva. Occasional great differences between serum and saliva values indicate that most of the salivary IgA and IgM (more than 90%) is produced locally at least in some individuals. The local anti-Yersinia response was restricted to IgA in some individuals, to IgM in others, whilst yet other patients produced salivary antibodies of both isotypes.     

Prolonged and preferential production of polymeric immunoglobulin A in response to Streptococcus pneumoniae capsular polysaccharides.

Streptococcus pneumoniae is an invasive mucosal pathogen for which host defense is dependent on capsular polysaccharide-specific antibody. Capsule-specific immunoglobulin G (IgG), IgM, and IgA are produced following pneumococcal vaccination and infection. Serum IgA has two molecular forms, polymeric and monomeric. These forms may modulate the avidity of antigen binding and evolve over time as the immune response matures. Therefore, we sequentially characterized the molecular forms of serum IgA to three serotypes of pneumococcal capsular polysaccharides (types 8, 12F, and 14) after pneumococcal vaccination and after natural infection with type 14 S. pneumoniae. Although typically the form of IgA in antigen-specific systemic responses to protein antigens is predominantly polymeric in sera of patients shortly after exposure and shifts to the monomeric form in sera obtained several weeks later, the form of IgA in response to each pneumococcal capsular polysaccharide remained predominantly polymeric 1 month after natural infection and up to I year following vaccination. In contrast, IgA to pneumococcal cell wall polysaccharide was both polymeric and monomeric. Moreover, the form of IgA in response to polyribosyl-ribitol-phosphate (PRP), the capsular polysaccharide of Haemophilus influenzae type b, was predominantly monomeric in the sera of 8 of 10 subjects tested 1 to 3 months after vaccination with either PRP alone or the diphtheria toxoid conjugate of PRP. We conclude that systemic responses to pneumococcal capsular polysaccharides are distinct in the production of predominantly polymeric IgA over time. The persistence of polymeric IgA may facilitate binding and clearance of pneumococci from the systemic circulation or reflect limited maturation of the immune response to pneumococcal capsular polysaccharides.     

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.     

Secretory immune responses to Mycoplasma pulmonis.

Formalinized Mycoplasma pulmonis, along with aluminum hydroxide as an adjuvant, was used to subcutaneously immunize rats in the vicinity of the salivary gland to examine the characteristics of the secretory immune response to this pathogen. The induction of specific antibody to this microorganism was detected in serum and the exocrine fluids, namely, saliva and lung lavage fluid. Both immunoglobulin G (IgG) and IgA isotype antibodies were detected in each of these fluids after primary and secondary local immunizations. Serum responses from immunized animals were significantly greater than in the control group, but a dose response was not observed in either IgG or IgA antibody at the dosages selected for immunization. Salivary IgG antibody responses peaked early after both the primary and secondary immunizations, exhibiting a clear dose response. Salivary IgA in immunized groups was significantly greater than that in the control group but displayed little dose-dependent kinetics, and, at the termination of the experiment, this response had not yet peaked. Lung lavage IgG and IgA were minimal after the primary immunization when the antibody was normalized to total protein but displayed dose-dependent kinetics after a secondary challenge. IgG peaked immediately after a secondary challenge, while IgA peak responses were observed only after 20 days. A positive correlation was noted between the serum, saliva, and lung lavage fluid IgGs after both primary and secondary immunizations and only after a secondary challenge for IgA. In this study we were able to elicit a secretory immune response, consisting of both IgG and IgA, which exhibited a dose-dependent characteristic in lung lavage fluid to this immunogen. Additionally, a positive correlation of antibody levels between saliva and lung lavage fluid suggests that saliva could be used as an indicator for monitoring specific antibody to M. pulmonis in lung lavage secretions without requiring invasive, deleterious procedures.