Detection of high titres of Toxoplasma gondii antibodies in sera of patients with leprosy in Pakistan

Untreated and treated leprosy patients and their household contacts were screened for antibody to Toxoplasma gondii using antigen-coated latex particles. A significantly high level of seroprevalence (29.6%) was observed in the untreated leprosy patients compared to endemic controls (P < 0.01) with a mean reciprocal antibody titre of 20,007 +/- 3580 (n = 98) in seropositive patients. In treated patients seroprevalence dropped to 13.5%. Seroprevalence in a group of household contacts of leprosy patients was similar to that of control subjects from an endemic area but not exposed to leprosy (7.8% and 6.1% respectively), indicating that the increased seroprevalence in leprosy patients was not merely due to increased exposure related to socioeconomic factors. Antigenic cross-reactivity between T. gondii and Mycobacterium leprae antigens was ruled out by cross inhibition experiments carried out with soluble antigens from each of the organisms. We believe these antibodies may be induced by an increase in T. gondii load in leprosy due to a transient reactivation of latent T. gondii infections, as the antibodies in these leprosy patients were not associated with any sign of eye or lymphatic pathology related to toxoplasmosis.

Control of allergic reactivity in human filariasis. Predominant localization of blocking antibody to the IgG4 subclass

Patients with chronic helminth infections, despite having abundant basophils and mast cells specifically sensitized with antiparasite IgE and often exposed repeatedly to parasite Ag, rarely manifest allergic symptoms. This control of clinical allergic reactivity likely results from Ag-specific IgG "blocking antibodies" shown previously to be abundant in the sera of such patients. In the present study we used two approaches to determine in which of the four IgG subclasses this blocking activity was localized. First, specific antifilarial antibodies of each of the four IgG subclasses were quantified in the sera of 28 patients with Bancroftian filariasis and correlated with the levels of blocking activity in these sera (determined by histamine release assays). A significant correlation with blocking activity was seen only for antibodies of the IgG4 subclass, and, indeed, the correlation was especially strong in the group of totally asymptomatic patients (but with microfilariae circulating in the blood) in whom blocking antibody levels were highest. Interestingly, however, if the analysis excluded these asymptomatic microfilaremic patients and focused instead on those with lymphatic inflammatory pathology (who had relatively low levels of both serum blocking activity and specific IgG4 antibodies), then the small amount of blocking activity found in these sera correlated only with the levels of IgG1 subclass antibodies. The second approach utilized selective depletion of IgG4 (by anti-IgG4 affinity columns) from the sera of three microfilaremic patients with high levels of blocking activity and demonstrated clearly that removal of IgG4 abolished the majority of the blocking activity in these sera (53, 78, and 81%). These two sets of findings demonstrate a predominant role for specific IgG4 antibodies in blocking IgE-mediated allergic responses to the parasite Ag in vitro, but they also indicate that in some situations IgG1 antibodies can block such reactions. Furthermore, the correlation demonstrated between patients' clinical presentations and the levels of both their specific IgG4 antibodies and serum blocking activity suggests that these antibodies play a similar role in vivo as well.

Control of allergic reactivity in human filariasis. Predominant localization of blocking antibody to the IgG4 subclass

Patients with chronic helminth infections, despite having abundant basophils and mast cells specifically sensitized with antiparasite IgE and often exposed repeatedly to parasite Ag, rarely manifest allergic symptoms. This control of clinical allergic reactivity likely results from Ag-specific IgG "blocking antibodies" shown previously to be abundant in the sera of such patients. In the present study we used two approaches to determine in which of the four IgG subclasses this blocking activity was localized. First, specific antifilarial antibodies of each of the four IgG subclasses were quantified in the sera of 28 patients with Bancroftian filariasis and correlated with the levels of blocking activity in these sera (determined by histamine release assays). A significant correlation with blocking activity was seen only for antibodies of the IgG4 subclass, and, indeed, the correlation was especially strong in the group of totally asymptomatic patients (but with microfilariae circulating in the blood) in whom blocking antibody levels were highest. Interestingly, however, if the analysis excluded these asymptomatic microfilaremic patients and focused instead on those with lymphatic inflammatory pathology (who had relatively low levels of both serum blocking activity and specific IgG4 antibodies), then the small amount of blocking activity found in these sera correlated only with the levels of IgG1 subclass antibodies. The second approach utilized selective depletion of IgG4 (by anti-IgG4 affinity columns) from the sera of three microfilaremic patients with high levels of blocking activity and demonstrated clearly that removal of IgG4 abolished the majority of the blocking activity in these sera (53, 78, and 81%). These two sets of findings demonstrate a predominant role for specific IgG4 antibodies in blocking IgE-mediated allergic responses to the parasite Ag in vitro, but they also indicate that in some situations IgG1 antibodies can block such reactions. Furthermore, the correlation demonstrated between patients' clinical presentations and the levels of both their specific IgG4 antibodies and serum blocking activity suggests that these antibodies play a similar role in vivo as well.

Experience of erythropoietin in anemia of end stage renal disease

Recombinant human erythropoietin 50 units/kg intravenous twice a week was given to 9 anemic patients and end stage renal disease (ESRD) who were undergoing dialysis at the Kidney Centre. Of the total, 8 required no transfusion since the initiation of therapy and their haematocrit increased to approximately 29% or more with the improvement in general condition, sense of well being and exercise tolerance. One patient showed an increase in serum creatinine and two iron deficiency during therapy. In all cases blood pressure remained adequately controlled. No organ dysfunction or any other complication was observed.

Possible transmission of Mycobacterium leprae in a group of UK leprosy contacts

A case of infectious leprosy in residential accommodation in the UK prompted a study of the cellular and humoral response to Mycobacterium leprae in two groups of individuals who were in contact with the index case for almost a year. In the younger staff group (mean age 44 years) 23 of 30 individuals had positive Mitsuda skin tests, 25 showed lymphocyte transformation to a soluble sonciate of M leprae and 2 had slightly raised IgM antibody concentrations to the terminal disaccharide of M leprae phenolic glycolipid-1. In the older group of residents (mean age 83 years) 7 of 36 individuals were skin-test positive, 25 of 33 were positive by lymphocyte transformation, but none had raised antibody levels. When retested on two further occasions, the same 2 individuals in the younger group still had raised antibody concentrations, 1 of whom had a persistent lepromin skin-test response for over 8 months and showed a pronounced increase in lymphocyte transformation to mycobacterial antigens. The findings suggest that transmission of M leprae may have occurred in these 2 contacts, who were therefore given 6 months' chemoprophylaxis with rifampicin.

Application of a polymerase chain reaction for the detection of Mycobacterium leprae in skin tissues

The polymerase chain reaction (PCR) based on the selective amplification of a 530-bp fragment of the gene encoding the proline-rich antigen of Mycobacterium leprae was applied on sections of fixed or frozen biopsy samples from leprosy patients. A simple procedure for the extraction of DNA from M. leprae in clinical specimens that provided suitable template DNA for amplification was developed. When PCR was applied on frozen sections, positive amplification in samples from all untreated acid-fast bacillus (AFB)-positive patients and in samples from 56% of the untreated AFB-negative patients could be detected, while biopsy samples from patients with skin diseases other than leprosy were all PCR negative. With neutral Formalin-fixed biopsy samples, positive amplification in 92% of the samples from untreated AFB-positive patients and in 61% of the samples from untreated AFB-negative patients could be detected by PCR. Biopsy samples exposed to mercuric chloride or nonbuffered formaldehyde containing fixatives were not suitable for application of PCR. This PCR holds promise as a tool for studies on M. leprae infection.

Assurance of consistent peak-velocity measurements with a variety of duplex Doppler instruments

To assess the need for quality control when measuring peak velocities with Doppler ultrasonography, 17 duplex Doppler instruments from six manufacturers were compared by using a flow phantom that had been calibrated for peak velocities ranging from 23 to 75 cm/sec. Variations in peak-velocity measurements among machines averaged 23% when tested at the same flow rate with a Doppler flow phantom, indicating that scientific articles that document peak velocities for various disease processes should be accompanied by equipment calibration data. Doppler string and flow phantoms were compared, and each was found to have deficiencies. Techniques for quality assurance procedures for Doppler measurements are given that should achieve consistent peak-velocity measurements on serial scans of patients undergoing treatment for vascular conditions.

Quantitation of IgM antibodies to the M. leprae synthetic disaccharide can predict early bacterial multiplication in leprosy

Quantitative enzyme-linked immunosorbent assays detecting IgM to the soluble Mycobacterium leprae crude sonicate (CD75) and the synthetic disaccharide antigen coupled to bovine serum albumin (ND-BSA) were assessed for their ability to determine early infection in families/household contacts of leprosy patients and employees of a leprosy center working in close contact with leprosy patients. Although IgM to both antigens (CD75 and ND-BSA) correlated with the bacterial index (BI) assessed histologically on skin-biopsy samples, the level of IgM antibodies to ND-BSA was a much more sensitive indicator of low bacterial loads. A 4.4-fold difference in antibody levels was observed between the mean group levels of endemic controls (N = 116) and tuberculoid leprosy patients with a BI of 0 (N = 88), increasing to sevenfold in tuberculoid leprosy patients with a BI of 1 (N = 20). Using a statistical cut off with endemic controls (mean + 2 S.D.), household/family contacts showed 30% seropositivity (N = 180) as compared to staff contacts who showed 17% seropositivity (N = 55). Percent seropositivity in family contacts was not related to the type of leprosy of the index case (lepromatous vs. tuberculoid) or the duration of treatment of the index case. Age of the individual in the family contact group had a significant influence on seropositivity. These results support the hypothesis that, in this community, factors other than the viable bacterial load of the index case, such as genetic susceptibility, may be influencing the high rate of seropositivity in family contacts. IgM ND-BSA antibodies seem to provide a good indicator of low antigenic loads and could prove to be useful in detecting subclinical infection before the onset of disease. Follow-up studies of these seropositive individuals are in progress to understand the relationship between seropositivity and the progress of clinical disease.

Quantitative antibody ELISA for leprosy

Quantitative enzyme-linked immunosorbent assays (ELISAs) were established to measure IgM and IgG antibody levels to soluble Mycobacterium leprae sonicate (CD60) and to the synthetic disaccharide antigen based on the phenolic glycolipid-I antigen of M. leprae coupled to bovine serum albumin in 46 leprosy patients. Separate reference pools for IgM and IgG antibody were established. The reciprocal of the antibody titer was expressed as the number of arbitrary units in the reference pools which was subsequently used as the calibrator for assessment of units in individual test sera. The dose-response relationship for both IgM and IgG was highly specific and reproducible for both isotypes, as indicated by the intra- and inter-assay coefficients of variation. The distribution of antibody levels are in general agreement with the results from previous studies against different M. leprae antigens. The lepromatous group showed 10- to 100-fold higher IgM antibodies to both the soluble sonicate antigen and the disaccharide as compared to the control group. Very low to undetectable levels of IgM antibodies were observed in the tuberculoid group of leprosy patients. IgG antibodies, on the other hand, were not only present but showed considerable overlap with the lepromatous patient group. Optimized ELISAs, such as the one described in this study, would allow one to address issues such as antibody changes with treatment, antigen clearance, and correlation with other immune parameters associated with disease pathogenesis and protection.

Cellular immune responses of leprosy contacts to fractionated Mycobacterium leprae antigens

Antigens of armadillo-derived Mycobacterium leprae sonic extract were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto a nitrocellulose membrane, and the unstained blot was converted into 20 fractions of antigen-bearing particles. These were tested in cellular proliferation assays, and reproducible results were obtained between batches of fractions. Peripheral blood mononuclear cells from healthy contacts of leprosy patients (presumed to have protective immunity) were tested with the fractions to investigate which antigens they recognized. A small group of tuberculoid leprosy patients were also tested. Both groups showed a wide range of responses. Almost every fraction stimulated proliferation with at least one donor, yet none was clearly immunodominant or inhibitory in either group. Thus, protective immunity did not appear to be associated with proliferation caused by any single fraction.

T-cell recognition of the 18-kilodalton antigen of Mycobacterium leprae

The 18-kilodalton (kDa) antigen of Mycobacterium leprae was expressed as a fusion protein with a 2-kDa leader peptide and used in proliferation assays with peripheral blood cells. Fifty percent of untreated tuberculoid leprosy patients and 93% of long-term leprosy contacts responded to the recombinant protein in lymphocyte transformation tests. Comparison of the stimulation indices in the two groups showed that the contacts responded more strongly than the tuberculoid leprosy patients. Seventy percent of Mycobacterium bovis BCG-vaccinated European donors responded, although with low stimulation indices. The isolation of 18-kDa antigen-responsive T-cell lines from a BCG-vaccinated British donor confirmed that the 18-kDa antigen contains at least one cross-reactive epitope. These results indicate that the 18-kDa protein is an important antigen in the immune response to leprosy.

Parallel recognition of filarial antigens by IgE and IgG4 antibodies

IgE responses are highly modulated in human filariasis and allergic symptoms usually associated with IgE antibodies are seldom observed in individuals with Elephantiasis and Microfilaremia. Only a minor group with tropical pulmonary eosinophilia (TPE) suffer from nocturnal asthma. One possible mechanism may be the presence of IgG blocking antibodies which can block IgE mediated histamine release in vitro. Using immunoblot analysis we have further shown that remarkably similar pattern of antigen recognition were obtained with IgE and IgG antibodies which would be a major prerequisite for the blocking activity. In the present study, we have tried to determine if a particular IgG subclass is responsible for the parallelism seen with IgE antibodies. Immunoblotting with autoradiographic analysis was used to study IgE and IgG subclasses using highly characterized radiolabeled antibodies in 24 sera representing all three groups mentioned above. The most striking observation was that in 23/24 sera, the only antibody that showed consistent and parallel binding was IgG4. No consistent pattern of response was seen with any of the other three subclasses. IgG1 and 2 when present were usually directed predominantly to the high molecular weight antigens and were detected with greater frequency in Elephantiasis group. These results suggest that IgG4 may be an ideal candidate for the blocking activity seen in these sera. Such modulation of IgE responses may have important survival value for the host in filarial infection which tend to evoke rigorous IgE responses.

The structure of phenindamine base and salts in the solute state

High-field NMR (13C and 1H) studies of phenindamine are reported which establish structures of the free base and some of its salts in the solute condition. The base exists as a mixture of two isomers which differ in double bond position (9-9a or 4a-9a) while most salts are 9-9a isomers. The clinically employed tartrate (Thephorin) is exceptional in being a 4a-9a ene. Salts of both double bond type exist in solution as mixtures of protonated epimers of variable epimeric ratio, that of the tartrate in D2O being approximately 1:1.

IgG antibody subclasses in human filariasis. Differential subclass recognition of parasite antigens correlates with different clinical manifestations of infection

The four subclasses of IgG are distinct in structure, function, and degree of participation in the antibody response to complex antigens. Looking for differential responsiveness of potential pathogenetic significance, we have analyzed both quantitatively and qualitatively the filaria-specific IgG subclass responses of 20 patients with lymphatic filariasis presenting either with chronic lymphatic obstructive pathology and elephantiasis (CP) or with asymptomatic microfilaremia (MF). Subclass-specific monoclonal antibodies were used in an enzyme-linked immunosorbent assay to study IgG filarial antibodies quantitatively and in immunoblot analyses to determine qualitatively the subclass antibody specificities. Quantitatively, the most significant differences among patient groups were in levels of IgG4, which were more than 17 times higher in MF patients (geometric mean, 64.7 micrograms/ml) than in those with CP (mean, 3.7 micrograms/ml). When qualitative analyses were done on the same sera, major differences were noted, particularly in the recognition profiles of the IgG1, IgG3, and IgG4 responses. IgG1 and IgG3 responses to antigens were seen especially to antigens with m.w. greater than 68,000 in all patients with elephantiasis, whereas MF patients showed most of their reactivity to antigens less than 68,000. For IgG4, the MF patients showed prominent recognition of antigens throughout the entire range of m.w., whereas those with CP had very little IgG4 recognition of antigens of any m.w. Interestingly, this relationship was essentially reversed in the IgG3 antibody responses (especially to antigens greater than 68,000) and, to a lesser extent, the IgG1 responses. These findings demonstrate correlations of potential cause/effect significance between IgG4 antibody responsiveness and the immunomodulated asymptomatic MF form of clinical filariasis and between IgG3/IgG1 antibody responsiveness and the clinical presentation of CP.

IgG antibody subclasses in human filariasis. Differential subclass recognition of parasite antigens correlates with different clinical manifestations of infection

The four subclasses of IgG are distinct in structure, function, and degree of participation in the antibody response to complex antigens. Looking for differential responsiveness of potential pathogenetic significance, we have analyzed both quantitatively and qualitatively the filaria-specific IgG subclass responses of 20 patients with lymphatic filariasis presenting either with chronic lymphatic obstructive pathology and elephantiasis (CP) or with asymptomatic microfilaremia (MF). Subclass-specific monoclonal antibodies were used in an enzyme-linked immunosorbent assay to study IgG filarial antibodies quantitatively and in immunoblot analyses to determine qualitatively the subclass antibody specificities. Quantitatively, the most significant differences among patient groups were in levels of IgG4, which were more than 17 times higher in MF patients (geometric mean, 64.7 micrograms/ml) than in those with CP (mean, 3.7 micrograms/ml). When qualitative analyses were done on the same sera, major differences were noted, particularly in the recognition profiles of the IgG1, IgG3, and IgG4 responses. IgG1 and IgG3 responses to antigens were seen especially to antigens with m.w. greater than 68,000 in all patients with elephantiasis, whereas MF patients showed most of their reactivity to antigens less than 68,000. For IgG4, the MF patients showed prominent recognition of antigens throughout the entire range of m.w., whereas those with CP had very little IgG4 recognition of antigens of any m.w. Interestingly, this relationship was essentially reversed in the IgG3 antibody responses (especially to antigens greater than 68,000) and, to a lesser extent, the IgG1 responses. These findings demonstrate correlations of potential cause/effect significance between IgG4 antibody responsiveness and the immunomodulated asymptomatic MF form of clinical filariasis and between IgG3/IgG1 antibody responsiveness and the clinical presentation of CP.

The clinical and immunologic responses of normal human volunteers to low dose hookworm (Necator americanus) infection

Five normal human volunteers were exposed to approximately 50 infective larvae of Necator americanus and were observed for the development of clinical signs or symptoms and for changes in blood eosinophil levels, IgG antibody titers, total and parasite-specific IgE, and lymphocyte blastogenic responses for 6-10 weeks. Bronchoalveolar lavage was performed on four subjects prior to infection and at times when larval migration through the pulmonary tree was likely. Eggs were demonstrated in the stools of four volunteers who remained untreated for more than 6 weeks; one volunteer had to be treated at day 40 because of severe gastrointestinal symptoms. All others also complained of abdominal pain and flatulence between days 35-40. All volunteers developed marked blood eosinophilia which peaked between days 38-64 and ranged from 1,350-3,828 eosinophils/mm3. Small increases in total and parasite-specific IgE and IgG were noted in some volunteers. One volunteer showed a significant lymphocyte blastogenic response. With the exception of mucosal erythema, bronchoalveolar lavage results were unremarkable. Our data indicate that a single small inoculum of hookworm larvae is capable of producing significant transient gastrointestinal morbidity and marked blood eosinophilia but does not induce other prominent T cell- and B cell-dependent immune responses.

Use of monoclonal antibodies to quantify subclasses of human IgG. II. Enzyme immunoassay to define antigen specific (anti-filarial) IgG subclass antibodies

Because of their single epitope specificity, monoclonal antibodies (Mcabs) may perform with different levels of efficiency in immunoassays depending on the accessibility of the particular epitope recognized. In order to develop assays capable of detecting specific antibodies of each of the four human IgG subclasses, we have evaluated by ELISA the performance characteristics of a panel of Mcabs raised to the subclass proteins. At least one Mcab to each of the four subclasses was identified that was specific in its ability to capture its own relevant IgG subclass without any associated light chain, allotype or isoallotype activity and that was able to function effectively as a probe in an optimized, quantitative ELISA. When IgG subclass antibodies were measured in sera from patients with filariasis using specific filarial antigen, the sensitivities of each subclass antibody assay varied; for IgG1 and IgG4 antibodies the sensitivity of detection was 50 ng/ml and for IgG2 and IgG3, 10 ng/ml. The potency of the Mcab, determined by its titration for use as a probe, did not correlate with the sensitivity of the assay. These Mcabs were also capable of defining IgG subclass antibody responses qualitatively in immunoblot analyses with little or no non-specific binding. The availability of such highly characterized Mcabs for use in quantitative and qualitative definition of specific IgG subclass antibody responses should greatly improve our detection and subsequent understanding of the role of these IgG subclasses in various disease states.

Use of monoclonal antibodies to quantify subclasses of human IgG. I. Development of two-site immunoenzymometric assays for total IgG subclass determinations

Dissection of the IgG antibody response into its subclass components has been difficult largely because of the lack of adequate supplies of specific reagents. The development of monoclonal antibodies (Mcab) promises to overcome this problem, but the use of such antibodies has certain inherent problems. It has been shown recently that Mcabs which were avid, potent and specific for well defined epitopes may partially or completely lose their activity depending on the assay system in which they were used. In order to identify Mcabs that would be specific and useful as capture antibodies in a simple two-site enzymometric assay, a panel of 18 Mcabs was screened and one Mcab to each of the four IgG subclasses was identified for quantitation of subclass levels in human serum.

Time-resolved X-ray diffraction studies of the B in equilibrium D structural transition in the DNA double helix

Because of the relation between topology and function, there has been much interest in the structural transitions of the various conformations of DNA polymers. The x-ray fiber diffraction analysis system at the Daresbury Synchrotron Radiation Source was used to study the reversible transition between the B and D forms of the synthetic DNA poly[d(A-T)].poly[d(A-T)]. The gradual progression of conformations between these two forms indicates that the DNA double helix does not undergo a change of handedness during this transition.

IgE responses in human filariasis. IV. Parallel antigen recognition by IgE and IgG4 subclass antibodies

Immediate hypersensitivity responses are highly modulated in filariasis, and with few exceptions, the majority of infected individuals do not develop allergic manifestations. One possible mechanism for this modulated responsiveness could involve the high levels of IgG "blocking antibodies" shown to be present in filariasis and other chronic helminth infections. When immunoblot analyses were done to analyze the immunoglobulin (Ig) E and IgG antibody responses of patients simultaneously, remarkable similarity in the patterns of antigen binding was observed. In this study, the four IgG subclasses were analyzed in a similar manner in relation to IgE. The results clearly demonstrate that IgG4 was primarily responsible for this "parallel" recognition that was seen previously between IgG and IgE antibodies. These results lend additional support to the possibility that IgG4 may play an important role in modulating IgE-mediated allergic responses in vivo.

IgE responses in human filariasis. IV. Parallel antigen recognition by IgE and IgG4 subclass antibodies

Immediate hypersensitivity responses are highly modulated in filariasis, and with few exceptions, the majority of infected individuals do not develop allergic manifestations. One possible mechanism for this modulated responsiveness could involve the high levels of IgG "blocking antibodies" shown to be present in filariasis and other chronic helminth infections. When immunoblot analyses were done to analyze the immunoglobulin (Ig) E and IgG antibody responses of patients simultaneously, remarkable similarity in the patterns of antigen binding was observed. In this study, the four IgG subclasses were analyzed in a similar manner in relation to IgE. The results clearly demonstrate that IgG4 was primarily responsible for this "parallel" recognition that was seen previously between IgG and IgE antibodies. These results lend additional support to the possibility that IgG4 may play an important role in modulating IgE-mediated allergic responses in vivo.

Comparison of immunoblot and immunoprecipitation methods for analyzing cross-reactive antibodies to filarial antigens

Qualitative analysis of antibody responses in helminth infections is essential not only for developing better immunodiagnostic antigens but also for understanding immune recognition and its relevance to immunopathogenesis and protective immunity. In this study 2 qualitative analytic methods (immunoprecipitation and immunoblotting) were compared for the ability to define the extent of cross-reactivity in the serum antibodies from patients with various forms of filariasis (caused by Brugia malayi, Wuchereria bancrofti, Loa loa and Tetrapetalonema perstans) or other non filarial helminth infections (ascariasis, strongyloidiasis, trichinosis, echinococcosis and schistosomiasis). Our results demonstrated that the spectrum of cross-reactive antibodies identified by immunoprecipitation was limited because of the selective radiolabeling of particular filarial antigens, while immunoblotting was able to detect a much wider range of cross-reactive antibodies in both filarial and non-filarial serum pools. In addition, this latter procedure was easily adapted for simultaneous analysis of different antibody isotopes (e.g., IgE and IgG) to the same antigens in individual sera. Immunoblotting thus provides an excellent tool for studying the spectrum of antibodies of different isotypes evoked during helminth infections and for discriminating between those responses that are species-specific and those that are cross-reactive.

IgE responses in human filariasis. III. Specificities of IgE and IgG antibodies compared by immunoblot analysis

IgE and IgG immune responses were qualitatively characterized in three well-defined groups of patients with different clinical manifestations of lymphatic filariasis caused by infection with Wuchereria bancrofti; viz. tropical pulmonary eosinophilia (TPE), chronic lymphatic obstruction with elephantiasis (CP), and asymptomatic microfilaremia (MF). A complex filarial antigen preparation extracted from adult filarial parasites was separated on SDS-polyacrylamide gels, and was electrophoretically transferred to nitrocellulose paper before being incubated with individual sera and being probed with radiolabeled anti-IgE or protein A. Three clinical groups of patients showed distinct patterns of antigen recognition by both IgE and IgG antibodies, with TPE patients showing the most diverse patterns and microfilaremic individuals the most restricted responses for both antibody isotypes. "Dual recognition" of antigens by IgE and IgG antibodies seemed to be the rule rather than the exception for each individual's immune response to the parasite antigens, but the relative magnitudes of IgG and IgE responses differed among the three groups. The ratio of IgG to IgE antibody was generally greater in patients with MF and CP than in those with TPE. These findings of the comparative specificities and relative abundance of IgE and IgG antibodies in infected patients may have fundamental importance in explaining the clinical expression (especially allergic reactivity) and disease pathogenesis of human filarial infections.