The predominance of IgG1 and IgG3 subclass antisperm antibodies in infertile patients with serum antisperm antibodies.

Mouse monoclonal antibodies (MAb) specific for each of the four human IgG subclasses and immunofluorescence flow cytometry were used to evaluate the subclass of the IgG antibody response to sperm in serum samples from 13 men and 6 women with a high titer (greater than 1:15,625) of IgG antisperm antibodies (ASA] determined by an indirect immunobead test. Five sera without ASA were also studied as a control. All 19 (100%) of the ASA-positive sera contained immunoglobulin (Ig)G ASA of the IgG1 and IgG3 subclasses. A 1:1 correlation was observed between the presence of IgG1 and IgG3 ASA. IgG2 was essentially undetectable, while IgG4 reactivity, although less intense than IgG1 and IgG3, was more prominent in the sera from the five vasectomized men. The ability of the IgG1 and IgG3 ASA-positive sera to deposit complement (C) on sperm was demonstrated by the concomitant binding to antibody-laden sperm of polyclonal antibodies to the membrane attack complex (C5b-9) of C. Both C-fixing and non-C-fixing ASA-positive sera were found to possess IgG1 and IgG3 antisperm antibodies. The predominance of IgG1 and IgG3 subclasses suggested a T-cell dependent immune response to sperm antigens.     

ELISA quantitation of IgG subclass antibodies to dietary antigens

The IgG subclasses of human antibodies against 2 dietary antigens, ovalbumin (OA) and beta-lactoglobulin (BLG), were studied by ELISA using monoclonal anti-human IgG subclass antibodies. Under the assay conditions used, the anti-IgG subclass antibodies were subclass specific. Quantitative estimates of the subclass antibodies were obtained by reference to a 'capture' assay using F(ab')2 anti-light chain antibody as ligand and IgG myelomas as standards. The validity of these estimates was supported by antibody quantitation using the Farr assay. In healthy adults with serum anti-OA or anti-BLG antibodies, anti-OA antibodies were found mainly in the IgG1 (9/11) and IgG4 (6/11) subclasses, whereas 5 sera showed high levels of IgG2 antibodies. In contrast, the IgG subclass distribution of anti-BLG antibodies was predominantly IgG4 (10/10).     

Influence of the G2m(n) allotype and age on IgG subclass distribution in antibodies to dietary proteins in children with coeliac disease

In 47 children with coeliac disease, IgG1 was the dominant IgG subclass (mean 61%) in antibodies to gliadin, a protein component of wheat; IgG2 (22%) and IgG3 (15%) were also found. Very little IgG4 (3%) was detected. Both G2m(n)allotype and the age of the patient had an independent effect on the subclass distribution. The effects of these two factors seem similar to those described earlier on responses to polysaccharides; both G2m(n) and age increase the expression of IgG2 antibodies and concomitantly the share of IgG1 is decreased. The average increase in the share of IgG2 brought about by n/n-genotype was 25.3% (95% confidence limits 12.2-38.4%; P less than 0.001) and that brought about by each additional year of age of the patient 1.1% (0.3-1.9%; P = 0.006). IgG antibodies to beta-lactoglobulin and ovalbumin consisted mainly of IgG1 and IgG4. The titres of the IgG subclasses were low and in many cases below detection level. No association with G2m(n) genotype and share of IgG1 or IgG4 could be demonstrated. Age was inversely correlated with the shares of IgG1 in antibodies to beta-lactoglobulin and ovalbumin.     

Prospective estimation of IgG, IgG subclass and IgE antibodies to dietary proteins in infants with cow milk allergy

Prospectively, serum levels of IgE, specific IgE antibodies (AB) to whole cow milk protein (CMP), bovine se-albumin, bovine immunoglobulin, bovine lactoferrin, bovine lactalbumin and beta-lactoglobulin (BLG), IgG and IgG subclass antibodies to ovalbumin (OA) and BLG, and IgG4 RAST to CMP (bovine whey) were measured in 39 infants with cow milk protein allergy (CMPA) at birth (cord blood), at time of diagnosis and before and after milk challenge at the age of 12 months. Immunological measurements were also undertaken in 33 control infants without CMPA at birth, at 6 months and at 18 months. At no time, were differences found between the levels of IgG and IgG subclass AB to OA and BLG in control versus infants with CMPA. In the 39 infants with CMPA no correlation was found between the levels of IgE, IgG and IgG subclass AB in cord blood and subsequent levels of these values, irrespective of the type of CMPA (IgE-mediated (CMA) or non-IgE-mediated (CMI)), and irrespective of whether remission had occurred. In cord blood 25/33 (76%) of the infants with CMPA had specific IgE-AB to one or more of the bovine milk proteins indicating a prenatal intrauterine sensitization to cow milk protein. At 6 months the frequency of specific IgE-AB to bovine milk proteins was significantly (p less than 0.05) higher in infants with CMA versus CMI, and at 12 months total serum-IgE and the increase of these specific IGE-AB and RAST to CMP were significantly higher (p less than 0.05) in infants with persistent CMA. From 6 to 12 months withholding milk resulted in a significant fall in specific IgE-AB to CMP, and IgG, IgG1 and IgG4 anti-BLG followed by an increase after milk challenge. Decreasing levels of IgG anti-OA from birth to 6 months reflect passive maternal transfer of IgG through the placenta, and increasing levels of IgG anti-BLG, already from birth to 6 months, may represent an early exposure to CMP in all infants. Significantly higher levels (p less than 0.05) of IgG anti-OA AB, IgG1 and IgG4 anti-BLG AB were found in infants with persistent CMA, indicating a close relation between the synthesis of IgE and IgG and between IgE and IgG subclasses (IgG1 and IgG4) in symptomatic cow milk-allergic individuals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Enzyme-linked immunosorbent assay for subclass distribution of human IgG and IgA antigen-specific antibodies

In this study we describe an ELISA using monoclonal antibodies to IgG 1, 2, 3, 4, IgA1 and IgA2 for determining the subclass distribution of human-specific antibodies. No cross-reactivity of the subclass-specific reagents under the conditions used was observed. The sensitivity was 0.5 ng/ml for IgG1, 3, 4; 1.5 ng/ml for IgG2 and 50 ng/ml for IgA1 and IgA2. The reproducibility as described by the coefficient of variation calculated on repeated runs was 8-26% if the data were obtained by relating the absorbance values to a positive serum run in the assay, 17-58% when relating the OD figures to those of a standard myeloma plate. The method may be considered semiquantitative with high sensitivity and specificity, easy to handle and with small day-to-day variation. The assay has been applied to a number of antigens of protein and polysaccharide nature.     

Subclass distribution of IgG antibodies to the rat oesophagus stratum corneum (so-called anti-keratin antibodies) in rheumatoid arthritis.

Serum IgG, labelling the stratum corneum of the rat oesophagus epithelium, so-called anti-keratin antibodies (AKA) constitute the most specific marker for the diagnosis of rheumatoid arthritis. In this study, we investigated 31 IgG AKA-positive rheumatoid sera and 21 control sera from patients with non-rheumatoid inflammatory rheumatic diseases. The serum level of IgG1,2,3 and 4 was determined by radial immunodiffusion and the subclass distribution of IgG AKA by a three-step semi-quantitative immunofluorescence assay using standard monoclonal antibodies specific for each of the four human IgG subclasses. In the rheumatoid sera, the serum level of IgG1 was found to be significantly increased and the level of IgG2 significantly decreased with regard to the control sera, while the levels of IgG3 and 4 as well as total IgG were in the normal range. IgG1,2,3, and 4 AKA were detected in 27 (87%), 6 (19%), 4 (13%) and 11 (35%) of the 31 rheumatoid sera, respectively, and were found to be independent of the clinical and biological indices of the disease. In spite of inter-individual heterogeneity, two predominant profiles were distinguished: IgG1 (alone) and IgG(1 + 4), which together represented 18 sera (58%). The large predominance of IgG1 AKA and the quasi-absence of IgG2 AKA suggest that the recognized antigen may be partly comprised of protein. Moreover, the high frequency of occurrence of IgG4 AKA might result from chronic exposure to the eliciting antigen, which could be a genuine autoantigen since we demonstrated that it is also present in the stratum corneum of human epidermis.     

Anti-mitochondrial antibody IgG subclass distribution and affinity in primary biliary cirrhosis.

We have studied the total IgG subclass and anti-mitochondrial antibody (AMA) specific IgG subclass distribution in primary biliary cirrhosis (PBC) sera. In order to solve the problems caused by the differing affinities of subclass specific monoclonals and the competitive inhibition of antibodies in a whole serum assay, six sera were separated into subclass-specific fractions by affinity-depletion chromatography. AMA subclass distribution of 20 further sera from patients with PBC was assessed using conventional methods and the results were calibrated against one of the fractionated sera. Light chain distribution and AMA functional affinity were also assessed for the fractionated subclasses. Total amounts of IgG3 were significantly increased compared with normal controls. AMA were found in all IgG subclasses and not restricted predominantly to IgG3 as previously described. The functional affinity of IgG3 AMA is generally lower as compared with that of other subclasses. No light chain restriction was found.     

Specificity of IgG subclass antibodies in different clinical manifestations of leprosy.

We analysed specific IgG subclasses levels to Mycobacterium leprae sonicate extract (MSE), lipoarabinomannan B (LAM) and phenolic glycolipid I (PGL-I) in the sera of leprosy patients with different clinical manifestations. IgG2 was found to be the predominant antibody to MSE regardless of clinical manifestations, and IgG1 response was mostly seen in lepromatous patients. IgG3 reacted only rarely but IgG4 reacted relatively more in certain clinical groups such as borderline lepromatous and lepromatous with erythema nodosum leprosum (ENL) reaction. Most of the IgG subclass responses to MSE could be accounted for reactivity with LAM, suggesting that LAM is the major immunogen involved in the pathogenesis of leprosy. In contrast to LAM, PGL-I antigen showed considerably lower reactivities for IgG subclasses. An association between IgG subclass responses and clinical manifestations of leprosy was also seen. Whereas borderline lepromatous patients were found to have significantly higher levels of IgG2 and IgG4 to MSE, lepromatous patients had elevated levels of IgG1 and lower levels of IgG2. An interesting observation, however, was the significantly higher levels of IgG2 to LAM in the pure neuritic leprosy patients.     

Bacteroides gingivalis-specific serum IgG and IgA subclass antibodies in periodontal diseases

The level of serum IgM, IgG and IgA antibodies including IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2 subclass-specific antibodies to Bacteroides (Porphyromonas) gingivalis fimbriae and to lipopolysaccharide (LPS) were analysed in patients with different forms of periodontal disease (PD) and control subjects by ELISA. Among PD subjects, sera obtained from adult periodontitis (AP), rapidly progressive periodontitis (RPP) and gingivitis contained high titres of fimbriae-specific IgG antibodies (7500-15,000 ELISA units) followed by IgA (90-700 units) and IgM (30-90 units). In contrast, sera from localized juvenile periodontitis (LJP) subjects exhibited much lower titres of fimbriae-specific IgG (89 +/- 11 units), IgA (31 +/- 5 units) and IgM (17 +/- 3 units) antibodies. A similar response pattern was also seen in sera from normal subjects aged 35-41 years who practice normal oral hygiene, while sera of younger adults (aged 18-24) with superior hygiene did not have any antigen-specific antibodies. Analysis of IgG subclass anti-fimbriae responses revealed that the major response was IgG3 followed by IgG1, IgG2 and IgG4 in AP, RPP and gingivitis. Although lower, a similar pattern of IgG subclass titre was seen in LJP and normal subjects aged 35-41 years. When IgA subclass responses were measured in AP and RPP, higher titres of the fimbriae-specific response were noted with IgA1 when compared with IgA2. However, lower but approximately equal levels of fimbriae-specific IgA1 and IgA2 titres were seen in other PD groups. When anti-B. gingivalis LPS-specific responses were measured, the sera of AP patients contained high levels of IgG antibodies (2265 +/- 224 units) followed by IgA (411 +/- 90 units) and IgM (214 +/- 56 units). Further, IgG anti-LPS responses were mainly IgG2 followed by IgG4, IgG3 and IgG1. For IgA subclass responses, higher titres of anti-LPS-specific antibodies were noted in IgA2 subclass over IgA1. These results showed that higher anti-B. gingivalis antibody responses occur in PD when compared with healthy individuals and protein and lipid-carbohydrate antigens of B. gingivalis induce distinct patterns of antigen-specific IgG and IgA subclass responses.     

IgG subclass distribution of antibody responses to protein and polysaccharide mycobacterial antigens in leprosy and tuberculosis patients

Immunoenzymatic assays were developed for the measurement of antibodies against mycobacterial lipoarabinomannan (LAM), a cell-free proteic extract (CFX) of Mycobacterium leprae, and the 38-kD protein antigen of M. tuberculosis. Sera from 108 leprosy patients, belonging to all clinical–immunological forms of the spectrum, and 81 patients with localized or disseminated tuberculosis (TB) were tested for antibodies of the four IgG subclasses. Standard calibration curves were used to allow comparisons between results of different isotypes and specificities. Mean concentrations of total IgG antibodies were higher in the overall leprosy population than in TB patients. In leprosy, levels of anti-CFX increased from tuberculoid toward lepromatous forms, with a clear switch from IgG1 to IgG2 subclass predominance. A similar IgG1 to IgG2 conversion was observed in anti-LAM antibodies, although total levels of anti-LAM were similar in patients with tuberculoid and lepromatous forms. In TB, antibodies against polysaccharide and protein antigens were both predominantly of IgG1 subclass, whatever the patient's clinical status, although lower in disseminated forms, probably due to concomitant HIV infection. A hypergammaglobulinaemia was also found in most leprosy and TB patients. In TB this was due to increased IgG1 and IgG3, especially in HIV co-infected patients. Based on the current knowledge of the influence of T cell-secreted cytokines on human immunoglobulin isotype expression, these results do not fit with a putative role of Th1 (such as found in TB and tuberculoid leprosy (TT)) and Th2 (such as found in leprosy lepromatous (LL) leprosy) environment in the isotypy of antibody responses in mycobacterial infections. Nor do variations of isotypy according to pathological conditions seem to be related to the biochemical nature of antigens, since antibodies to LAM and protein antigens had comparable evolutions of their subclass distribution. Other factors are to be investigated in order to understand better the significance and possible roles of antibodies in mycobacterial diseases.     

Clinical significance of IgG subclass antibodies to wheat flour antigens in bakers

We measured the IgG subclass antibody levels to wheat flour in 42 bakers and 20 controls with an enzyme immunoassay. The levels of total IgG, IgG1 IgG2 and IgG4 antibodies were significantly higher in the bakers than in the unexposed controls. The presence of anti-wheat flour IgG subclass antibodies in the bakers was correlated with various clinical variables including IgE levels, duration of asthmatic or rhinitis symptoms, skin prick test response, peripheral blood eosinophil levels, bronchial histamine reactivity and responses to nasal challenge with wheat flour. The IgG subclass antibody levels of the total cohort of bakers did not correlate with any of the measured clinical variables. However, among men specific IgG4 and IgG1 antibody levels correlated negatively with total IgE levels and duration of rhinitis, respectively. We conclude that IgG and IgG subclass levels to wheat flour in bakers reflect exposure, but that it is not related to any specific clinical situation. The exact pathogenic role of these antibodies in the development of occupational asthma and rhinitis is thus not clear.     

Immunoglobulin class and IgG subclass distribution of anticardiolipin antibodies in patients with systemic lupus erythematosus and associated disorders.

The class and subclass distribution of an antibody response may give insight into the stimulating mechanism and likely effector functions. IgA, IgG and IgM anticardiolipin antibodies (aCL) were quantified in a consecutive series of 200 samples sent to an autoimmune serology laboratory to determine the relationships between aCL responses of each of these antibody classes and, in particular, whether there was any utility in the measurement of IgA aCL. Positive results for one of the three aCL isotypes were found in 105 samples (53%), and in 41 samples IgA aCL was detected (21%). However, amongst these unselected samples, little additional information was obtained by measurement of IgA aCL, which was found in conjunction with IgM or IgG aCL in all but five samples, and in these the isolated elevation of IgA aCL was only slight, and showed no disease specificity. The levels of each of the four IgG subclasses of aCL were measured in a subgroup of serum samples from 28 patients with autoimmune disease and from 29 patients with syphilis. Amongst the SLE patients IgG1 and IgG3 aCL were the predominant IgG subclasses, consistent with an antigen-driven, T cell-dependent antibody response. However, a subgroup of eight of the autoimmune subjects had predominant elevation of IgG2 aCL, possibly implying a role for T cell-independent antibody production to cardiolipin. Amongst the syphilis patients IgG1 and IgG3 aCL were also the predominant subclasses of aCL but IgG4 aCL were also detected in the majority of subjects, consistent with prolonged antigenic stimulation.     

Aberrant IgG subclass distribution to measles in healthy seropositive individuals, in patients with SSPE and in immunoglobulin-deficient patients

Sera from healthy seropositive donors, patients with acute measles, subacute sclerosing panencephalitis, common variable immunodeficiency, and CH gene deletions were analysed for anti-measles IgG1-4. Compared with other anti-viral immune responses of IgG1 and IgG3, an unusual predominance of specific IgG1 prevailed; only four out of a total of 68 patients showed anti-measles IgG3. Of the 17 healthy, measles seropositive serum donors, all showed specific IgG1, none showed IgG3 and six had IgG4. Eight out of 10 patients with SSPE showed an anti-measles IgG1 and IgG4 response while IgG3 was not seen. The IgG1 and IgG4 subclass patterns had some exceptions. Anti-measles IgG3 was found in five out of five patients with deletion of the gamma-1 encoding gene segments and in four out of 15 patients with recent measles antigen stimulation. The subclass pattern was suggested to reflect the immunological compromise associated with measles infections.     

IgG subclass antibodies against Parietaria judaica in normal and allergic subjects

IgG antibody response to the inhalant allergen Parietaria judaica (Pj) and IgG subclass distribution were studied in 82 normal subjects, divided into three groups according to age (0–1, 1–20, and 20–60 years) and in 32 allergic subjects aged 20–60 years. Both normal and allergic subjects showed an IgG response, and all had IgG1 antibodies specific for PjE. Serum IgG2, IgG3, and IgG4 against PjE were detectable in 36%, 46%, and 22% of normal subjects, and in 58%, 31%, and 65% of allergic subjects, respectively. A significant difference in class distribution between allergic and age-matched normal subjects was found only for IgG4 antibodies against PjE (65% and 17%; P<0.01). The ELISA results were also analyzed quantitatively, taking into account the relative proportion of specific antibodies. Thus, in normal subjects IgG1 antibodies showed a decreasing trend as the age rose, while no differences according to the age of the subject were found for IgG2 and IgG4. When data from allergic subjects (20–60 years) and the age-matched normal group were compared, they were different for the relative percentage of IgG2 only, showing for this a significantly lower value (P< 0.001). The present data indicate that normal and allergic subjects show differences in the IgG isotype distribution depending on their sensitivity and duration of allergen exposure.     

Bindine affinities of allergens from pollen, mites, and house dust for specific IgG subclass antibodies

The distribution and affinity of IgG subclasses against various aeroallergens were assessed by inhibition of specific antibody binding. Two parameters from the dose-response curves were taken as indicative of antibody affinity: the point of 50% inhibition and the value of the slopes on double-log plots. It was found that IgG4 antibody specific for aeroallergens (i.e., from pollens of several species of Gramineae, Olea europaea , and Parietaria judaica and from house dust) usually exhibits high affinity, except for Dermatophagoides pteronyssinus . High binding affinity was also displayed by IgGl subclass antibodies against the allergens of O. europaea and P. judaica . Distinct IgG subclass affinity profiles were observed for the allergens of grass pollen (i.e., Holcus lanatus ) and dust mites (i.e., D. pteronyssinus ). These results demonstrate that IgG subclass distribution, as well as antibody affinity, depends on the nature of the sensitizing allergen.     

Herpes simplex-specific IgG subclass response in herpetic keratitis

The measurement of the local IgG response in ocular Herpes simplex virus infection presents particular problems due to the difficulty in obtaining sufficient tear samples and the possible transudation of IgG from the serum to the inflamed eye. Using specific monoclonal antibodies to Human IgG subclasses in an enzyme-linked immunoabsorbant assay (ELISA) the local IgG antibody response in Herpes simplex keratitis was analysed. All serum samples from patients and controls contained quantifiable levels of HSV specific IgG1 and IgG4 antibody. Comparison of serum antibody levels with tear levels for patients showed that HSV specific IgG1 serum concentrations were 16.1 fold or more higher than in tears, whereas IgG4 concentrations were only 6.5 fold higher in serum than in tears. This difference was not apparent in the control group. Radioimmunoprecipitation assay of 35S-methionine labelled HSV antigens revealed only minor differences in the protein profiles produced by immunoprecipitation using serum or tear antibody. These results suggest a role for IgG4 antibodies in mucosal immunity in the eye as has been suggested for the mucosal surface of the lung.     

A comparative study of IgG subclass antibodies in patients allergic to wasp or bee venom

IgG1 and IgG4 antivenom antibody responses were compared in groups of patients who had experienced systemic reactions to wasp ( Vespula spp.) or bee stings. Pretreatment serum IgG4 antibody levels were low in both groups, but IgG4 antibodies were significantly raised in bee-allergic patients ( P <0.002), probably reflecting their greater exposure to stings than wasp-reactive patients. No direct or indirect relationships were found, in untreated bee or wasp patients, between IgG1, IgG4, or IgE antibody levels and the severity of a patient's last systemic reaction to a sting. After a 12-week course of venom immunotherapy (VIT), IgG1 antibodies increased significantly only in wasp-sensitive patients ( P <0.001), although both groups responded with marked increases in venom-specific IgG4 ( P <0.01). Wasp-allergic subjects who responded to VIT with high production of specific IgG4 showed the greatest increases (pre- to post-VIT) in IgE antibodies (P<0.05). This group also demonstrated a direct correlation ( P <0.05) between post-VIT levels of IgE and IgG1 antibodies, a finding contrary to an IgE-immunoregulatory role for IgG 1. High levels of venom-specific IgG1 alone, or in combination with IgG4, were not protective in three patients who suffered repeated adverse reactions to bee VIT, showing that absolute levels of IgG subclass antivaenom antibodies are not reliably indicative of clinical responsiveness in individual patients.     

Determination of IgG subclass antibodies against wheat flour antigens by an ELISA technique

We describe the assay conditions for an enzyme-linked immunoassay for the determination of IgG and IgG subclass antibodies in serum to water-soluble wheat flour antigens. The optimal antigen coating concentration was 5 micrograms/ml for total IgG, IgG1, IgG4 and 100 micrograms/ml for IgG2. Serial dilutions of test sera were used and commercially available monoclonal mouse anti-human IgG isotype antibodies (as ascites fluid) were diluted 1:500-1:1000. Specific wheat flour antibodies belonging to the IgG1, IgG2 and IgG4 subclasses were detected. Despite the lack of standardized isotype-specific second mouse monoclonal antibodies, the subclass antibody levels between flour-exposed bakers and controls could be compared. We observed significantly higher IgG1, IgG2, and IgG4 subclass antibodies among 23 bakers than among 12 non-exposed controls, but no IgG3 antibodies were detected. The differences in biological activities of the IgG subclass antibodies may explain the clinical and pathophysiological features for fluor-induced occupational allergic diseases among bakers.     

A triple antibody assay for the quantitation of plasma IgG subclass antibodies to acetylcholine receptors in patients with myasthenia gravis

Monoclonal anti-human IgG subclass antibodies have been used in an immunoprecipitation assay for the determination of anti-acetylcholine receptor IgG subclasses in plasma from patients with myasthenia gravis. Solubilized acetylcholine receptors labelled with 125I-alpha-bungarotoxin were incubated with patient plasma. Monoclonal mouse antibodies to human IgG subclasses 1-4 were added to the incubation and finally precipitated with anti-mouse IgG antibody. A maximal IgG subclass precipitation of 62-76% was determined with 125I-labelled myeloma IgG subclasses 1-4 added to normal human plasma. The anti-IgG subclass antibodies were added in excess which ensured that the precipitation of IgG2, IgG3 or IgG4 were unchanged, and that of IgG1 was only reduced by 17%, when the plasma IgG concentration was increased by a factor of two. The anti-IgG subclass antibodies were highly specific for their complementary subclasses. Determination of the IgG subclass of the anti-acetylcholine receptor antibodies from 8 patients with myasthenia gravis showed that IgG1 and IgG3 antibodies are predominant. This may support the hypothesis that complement mediated lysis of the neuromuscular end-plate plays a pathogenetic role in myasthenia gravis.     

IgG subclass antibodies to Pseudomonas aeruginosa in sera from patients with chronic Ps. aeruginosa infection investigated by ELISA

ELISAs using subclass-specific monoclonal antibodies were developed for the quantification of human IgG1, IgG2, IgG3 and IgG4 antibodies to Ps. aeruginosa. We investigated the pattern of IgG subclass antibodies against Ps. aeruginosa in serum from patients with cystic fibrosis (CF), other patients with chronic Ps. aeruginosa infection, and healthy controls. Healthy controls and patients with CF but without Ps. aeruginosa infection showed no or very low titres of antibodies against Ps. aeruginosa. In the early stage of chronic Ps. aeruginosa infection, antibody titres in all four subclasses were significantly higher than either normals or CF patients without infection. Other patients with Ps. aeruginosa infection showed the same increased level of IgG subclass antibodies as CF patients in an early stage of infection. Sixteen patients (eight in good and eight in poor clinical condition) have been followed for an average of 13 years with multiple serum samples covering the pre-infection, early and late stages of chronic infection. Patients in a poor clinical condition showed significantly higher levels of IgG3 antibodies in the first year of infection and 2 years later also had significantly higher IgG2 antibody levels. We conclude that elevated levels of IgG2 and IgG3 antibodies to Ps. aeruginosa are a sign of poor prognosis in CF.