Characterization of human autoantibodies that selectively precipitate the 7SL RNA component of the signal recognition particle

The signal recognition particle (SRP), which consists of the 7SL RNA molecule associated with six polypeptides ranging between 9,000 and 72,000 m.w., mediates the translocation of newly synthesized proteins across the endoplasmic reticulum. We have characterized autoantibodies that are directed against this particle from two patients with rheumatic diseases. These sera immunoprecipitated the 7SL RNA from whole extracts of HeLa cells radiolabeled with 32P, but no RNA from deproteinized cell extracts. From 35S-methionine-labeled cell extracts, they immunoprecipitated a single polypeptide of 54,000 m.w. that is consistent with a known SRP component. Sucrose density gradient studies confirmed that this protein co-migrated with the 7SL RNA, indicating the likelihood that it is physically associated with this RNA. Thus, the 54,000 m.w. SRP protein, which is essential for the SRP functions of elongation arrest and translocation, appears to be a preferential target for human autoimmune responses. Human autoantibodies that recognize the SRP should be useful adjuncts to animal antisera for studies of the structure and function of this particle.

Interactions between precipitating and nonprecipitating antibodies in the formation of immune complexes

In the present study, we used monoclonal antidinitrophenol (DNP) antibodies to determine certain of the biophysical characteristics of precipitating and nonprecipitating antibodies. In addition, we studied the dynamics of immune complex (IC) formation when precipitating antibodies react with antigen in the presence of nonprecipitating antibodies. The antigen utilized in these studies was DNP-bovine serum albumin. All isolated nonprecipitating anti-DNP antibodies were of the IgG2b isotype, whereas all antibodies with other isotypes (IgG1, IgG3, IgM, IgA and IgE) were precipitating. Nonprecipitating antibodies did not differ significantly from precipitating antibodies in affinity, valence, or isoelectric point. Nonprecipitating antibodies inhibited the formation of precipitable IC between antigen and precipitating antibodies. In addition, preformed IC precipitates were solubilized by nonprecipitating antibodies. The solubilization of IC precipitates was influenced by the isotype of the precipitating antibody and by the antibody:antigen ratio in the IC precipitate. By isokinetic sucrose density centrifugation, we determined that solubilization of IC precipitates by nonprecipitating antibodies was associated with release of free precipitating antibody and formation of soluble IC between the antigen and the nonprecipitating antibody. In conclusion, in this study the nonprecipitating property of mouse anti-DNP antibodies is isotype-specific. Nonprecipitating antibodies compete and displace precipitating antibodies from the antigen, resulting in inhibition of IC precipitation and in IC solubilization. On the basis of the present results, we postulate that antibody-antibody interactions are important determinants of precipitating ability, and that these interactions are a characteristic of antibody isotype.

A trivalent antigen for the detection of type I avian adenovirus precipitin

A double immunodiffusion antigen prepared from cell-culture-propagated CELO virus was not capable of detecting precipitin directed against all of the type I avian adenovirus (fowl adenoviruses) isolates tested. However, an antigen pool containing CELO-4, B-3, and IBH-2 (Tipton) fowl adenovirus isolates detected precipitin directed against representative isolates of 10 type I serotypes. Additionally, this antigen pool markedly improved detection of adenovirus field exposure.

Lipoarabinomannan and lipid-free arabinomannan antigens of Mycobacterium paratuberculosis

Lipoarabinomannan (LAM) and lipid-free arabinomannan (AM) were prepared from Mycobacterium paratuberculosis. Purification of LAM was done by ultracentrifugation of the phenol-water-extracted crude polysaccharide, followed by affinity and anion exchange chromatography. AM was purified from the supernatant of the ultracentrifuged polysaccharide or from alkaline-extracted material by gel filtration and anion exchange chromatography. Chemical analysis revealed arabinose and mannose in LAM (1.4:1) and AM (3.5:1) and the presence of palmitic, stearic, and tuberculostearic acids for a total of 7.8% lipid in LAM. Traces of phosphorus were found in the AMs, particularly LAM (0.05%). Nuclear magnetic resonance confirmed the presence of alpha-arabinosyl residues and the acylated nature of LAM. LAM exhibited lipid-dependent aggregation, as indicated by a Triton-induced decrease in molecular weight. By using bovine sera, LAM was found to be active in the complement fixation test, whereas AM was inactive and inhibited this activity. Thus, the presence of AM in crude polysaccharide could explain the variable complement fixation results. Triton-dissociated LAM exhibited a precipitin (Cl) in common with that of AM, confirming shared determinants. LAM in its lipid-dependent aggregated form, however, exhibited a second precipitin (C2), which may be due to the disparity in antigen size or a novel epitope. The lipid content of LAM rendered it 100 times more effective for coating plates in the enzyme immunoassay than lipid-free AM.

Structure of asymmetric non-precipitating antibody: presence of a carbohydrate residue in only one Fab region of the molecule

The reactions between purified precipitating and non-precipitating anti-DNP sheep and rabbit antibodies and the antigens DNP-BSA and DNP-GABA-BSA have been studied by immunodiffusion, complement fixation and an inhibition test. Both antigens reacted identically with precipitating antibodies. On the contrary, non-precipitating antibodies did not precipitate and did not fix complement with DNP-BSA but were able to do so with DNP-GABA-BSA. A different behaviour with both antigens was also demonstrated by an inhibition test. The properties of these antibodies were also studied after treatment with endo-beta-N-acetylglucosaminidase H. Non-precipitating antibody was able to give precipitin bands in gel diffusion and to fix complement with DNP-BSA after treatment with the enzyme. The treated antibody was able to agglutinate sensitized erythrocytes. Studies by fluorescence quenching showed that the affinity for the ligand DNP-GABA was significantly increased after hydrolysis of the carbohydrate residue. The properties of precipitating antibody were not modified by the endoglycosidase. Affinity chromatography of the F(ab')2 and Fab fragments obtained from precipitating and non-precipitating antibodies was made with Con A-Sepharose. The Con A retained all the F(ab')2 and 50% of the Fab from non-precipitating antibody, which were subsequently eluted with alpha-methyl-D-mannoside. The fragments from precipitating antibody were not retained at all. It is concluded that the asymmetry of the non-precipitating antibody molecule is due to a carbohydrate moiety which is present in only one of the Fab regions. This carbohydrate affects the reaction between the combining site and the antigen, and renders the molecule functionally univalent.

Isolation and purification of a Clq-anti Clq precipitin ring enhancing protein from sera of patients with rheumatoid arthritis

We have isolated and purified to apparent homogeneity a serum protein which appears to be a biological marker for active rheumatoid arthritis. The protein has been found in the sera in all 44 active rheumatoid arthritis patients thus far studied and is absent from, or present in undetected amounts, in sera from normal subjects or from patients with other arthritides. The protein has a molecular weight of 135,000 daltons, an isoelectric pH of 5.1-5.3, and it enhances the size of the C1q-anti C1q ring.

Factors affecting the development of precipitating antibodies in workers exposed to contaminated humidifiers

A total of 601 sera from groups of workers exposed to heavily and moderately contaminated humidifiers respectively were examined by the double diffusion test for precipitating antibodies to humidifier extracts. Clinical information was obtained using a standardized questionnaire. Skin-prick tests to control, to three common inhalant antigens and to an extract from the humidifier were performed in 103 subjects exposed to a heavily contaminated humidifier. In this environment a strong inverse relationship between current smoking and precipitins was detected (P less than 0.001). Pack years smoked had no bearing on precipitin level. In the larger study there was a clear dose response effect of smoking on precipitins. The effect of smoking appeared to reverse within 3 years. Duration of exposure also had a major effect on the development of precipitins with a clear 'dose response' again being seen in the larger study. These relationships did not apply in the groups exposed to moderately contaminated humidifiers. Levels of airborne antigen were measured using a competitive ELISA inhibition assay and were found to be much lower in sites with moderately contaminated humidifiers than at sites with heavily contaminated humidifiers. Our results suggest that the airborne antigen level is crucial in determining the pattern and strength of precipitin response in smokers and non-smokers exposed to contaminated humidifiers.

Specificities and characteristics of mitochondrial protein antigens assessed by enzyme linked immunosorbent assay for anti-mitochondrial antibodies. Relationship to immunofluorescent and precipitating antibodies

M-A, M-B and M-C are autoantibodies to mitochondrial proteins frequently found in primary biliary cirrhosis. To study the characteristics and specificities and to isolate antigens reacting with the autoantibodies a sensitive assay (ELISA) was established. Using this technique a significantly elevated level of antibodies was detected in patients with primary biliary cirrhosis (mean OD 460.2, s.d. 145.8) compared to normals (133.7 +/- 49.7). The assay correlated well with the indirect immunofluorescence test for detecting anti-mitochondrial antibodies and the mitochondrial fluorescence could be abolished by absorption of autoantibodies with the mitochondrial fraction. All three types of antibodies could be detected by ELISA; however, sera containing the combination of two or more antibodies yielded higher ELISA values. The ELISA confirmed that the M-A antigen is trypsin and acid (pH 3.0) sensitive but DNAase and RNAase resistant while the M-B antigen is DNAase and trypsin sensitive. The antigens were enriched in the supernatant isolated from the mitochondrial fraction centrifuged at 1,800 g for 60 min and 2% polyethylene glycol precipitates of the mitochondrial fraction. The antigens were found phosphate buffer soluble and therefore could also be enriched by phosphate buffer extraction of the mitochondrial proteins. Thus, ELISA described here provided a sensitive method in the assessment of characteristics and purification of autoantigens related to mitochondrial antibodies.

Factors influencing the development of serum precipitins to farmer's lung antigen in Quebec dairy farmers

A total of 888 randomly selected dairy farmers participated in an epidemiological study to evaluate the prevalence of precipitins to farmer's lung antigens, and the socioeconomic factors associated with their presence. Precipitins were present in 75 farmers (8.4%) (65 to Micropolyspora faeni, seven to Aspergillus spp, two to both Aspergillus and Micropolyspora faeni, and one to Aspergillus and Thermoactinomyces vulgaris). The titres ranged from a dilution of 1/32 to a concentration of X 2 (Ouchterlony's double diffusion method). In the study population there were 544 who had never smoked, 146 ex-smokers, and 198 smokers. Sixty nine precipitin positive subjects were either never smokers or ex-smokers; only six were smokers. The negative relationship between cigarette smoking and precipitins was highly significant (p = 0.004). Factors positively associated with positive precipitin reactions were: size of farm, time spent in the barn, and the presence of a family member previously diagnosed as having farmer's lung disease. Interestingly, positive precipitin reactions were not associated with any of the following: use of silos, hay conditioners, or hay dryers; the presence or quantity of mouldy hay; or the presence of respiratory symptoms. It is concluded that precipitin analysis is not useful as a screening method for farmer's lung, though it can be of diagnostic value in acute farmer's lung disease.

Isolation of an acidic polysaccharide antigen from Propionibacterium acnes

An acidic polysaccharide antigen is released from Propionibacterium acnes I and II during growth. The molecular weight of the antigen was heterogeneous and when fractionated on a Sepharose CL-6B column, the antigen was detected at Kav values of between 0.1 and 1.0. The pI of the antigen was below 3.5. Rabbit antiserum raised against purified acidic-polysaccharide agglutinated P. acnes showing that the polysaccharide was a surface antigen. Human antibodies towards whole P. acnes-II organisms were quantitated by an agglutination technique, and antibodies towards purified acidic polysaccharide were quantitated by single radial immunodiffusion. A high prevalence of antibodies against whole bacteria and the acidic polysaccharide was found in sera from healthy individuals. The antibody titre in sera from acne patients was significantly higher than that in sera from blood donors.

Standardization of Dermatophagoides pteronyssinus: assessment of potency and allergen content in ten coded extracts

As part of the studies to establish an international reference preparation of Dermatophagoides pteronyssinus allergens, ten coded extracts of this mite were assessed in four laboratories. The extracts were compared for total potency using direct RAST, RAST inhibition and quantitative skin tests, and also for composition and major allergen content using crossed immunoelectrophoresis, crossed radioimmunoelectrophoresis, rocket immunoelectrophoresis and radioimmunoassay. In addition, the source materials were examined by light microscopy, and the extracts were examined for the presence of proteins/allergens derived from the culture media. To help with standardization, a new reference pool of sera from patients allergic to D. pteronyssinus was also established (National Institute of Biological Standards and Control, NIBSC, 82/528). The results showed that techniques are available for measurements of potency and allergen content. In several of the extracts, culture medium derived allergens and antigens were demonstrated. It also became clear that extracts varied not only in their total potency but also in the distribution of the identifiable allergens. In particular, extracts derived from isolated mites contained more AgX and/or Ag 23 relative to their content of antigen P1 (= Ag42). These studies lead to the choice of an extract for an international reference preparation (NIBSC 82/518) and helped to establish the methods used subsequently in the international collaborative study.

Allergenic components of bald-faced hornet (V. maculata) venom

Bald-faced hornet (V. maculata) venom collected by electrical stimulation was fractionated using molecular exclusion gel-filtration and ion-exchange chromatography. Four fractions were selected for in-depth analysis. These were analyzed for phospholipase, hyaluronidase and protease enzyme activities, antigenicity as measured by reaction with anti-hornet venom rabbit serum, and allergenic activity, as determined by RAST reaction with sera from hornet-sensitive patients. The results of these studies suggest that the fractions containing phospholipase, hyaluronidase and protease possess allergenic activity. In addition, there appear to be other allergenic components in hornet venom. Allergic patients differ in their reactivity to the various allergenic components in hornet venom and may have IgE antibodies to one or more of these components.

Immunochemical studies on the binding properties of Brucella abortus lipopolysaccharides to bovine precipitating antibodies

The binding properties of Brucella abortus smooth lipopolysaccharides (LPS) to the precipitating antibodies in the serum of a B. abortus S2308 infected cow were studied by quantitative precipitin and precipitin-inhibition assays. Crude B. abortus lipopolysaccharides (cLPS) and chemical modification products of strains 1119.3, 19 and 2308 (virulent) were used for this study. In the quantitative precipitin assay, 13 micrograms of cLPS precipitated about 4.0-5.2 micrograms nitrogen of precipitating antibodies in 10 microliter of serum. After alkaline treatment (0.125 N NaOH at 56 degrees C for 1 hr), the alkali-treated lipopolysaccharides (aLPS) from S19 and S1119.3 maintained the maximum precipitability, but the precipitation profile was changed from a sigmoidal to a bell-shaped curve, and aLPS from S2308 was reduced to about 40% of its reactivity. These results indicate that some of the antigenic determinants blocked by other molecules were reshielded by alkaline treatment, and possibly that structural differences exist between virulent (S2308) and nonvirulent (S19 and S1119.3) strains. Among the monosaccharides and glycosides tested for inhibition of precipitation, methyl alpha-D-mannose was most active and about 3.3 times as active as D-mannopyranose (DMan) and only 1/200 as active as acid hapten or the carbohydrate moiety of cLPS prepared from S1119.3 (expressed as a monosaccharide of mol. wt 200) implying that the carbohydrate determinants of this antigen are probably related to a DMan alpha 1----linked compound. The precipitability of the antibodies in this serum was greatly reduced after absorption with cLPS and the precipitin reaction was completely inhibited by the carbohydrate moiety of LPS (O-antigen) S1119.3 demonstrating that the common antigenic determinants (hapten) of B. abortus LPS reacting with these precipitating antibodies are in the region of the carbohydrate moiety of the LPS.

Adverse transfusion reactions associated with a precipitating anti-C4 antibody of anti-Rodgers specificity

A patient suffering from chronic hepatitis exhibited severe transfusion reactions after administration of fresh frozen plasma and a plasma fraction: PPSB (prothrombin complex concentrate). 1 month before these reactions, she received fresh frozen plasma during plasma exchange therapy. The patient's serum obtained 1 week and 6 months after the second reaction gave a precipitation arc against PPSB preparations when examined by double-diffusion technique in agarose gel. An antibody of IgG class present in these sera reacted with a purified preparation of the fourth complement component (C4). This was demonstrated by various experiments (protein A radioimmunoassay and passive hemagglutination) using purified C4 as antigen. The antibody had a limited specificity and reacted only with C4 of Rodgers specificity. Phenotype determination of the patient's C4 group showed that she was Chido positive and Rodgers negative. Her HLA group was A1, Aw30; B8,-; DR3,-. The patient had neither detectable anti-IgA nor other anti-immunoglobulin antibodies. She had not received blood or plasma transfusion before her hepatitis. The coexistence of a precipitating anti-C4 antibody and adverse transfusion reactions to plasma fractions containing large amounts of C4 indicates that in the absence of antibodies of other specificities, this antibody can be considered as the cause of the transfusion reaction.

Relationships between antinuclear and anti-Ro/SS-A antibodies in subacute cutaneous lupus erythematosus

A certain degree of confusion has arisen regarding the relationship between patients having subacute cutaneous lupus erythematosus (SCLE) and those with "antinuclear antibody-negative" systemic lupus erythematosus (ANA-negative SLE). One of the confusing issues relates to published differences in the autoimmune serologic findings of these two patient groups. In order to clarify this issue, we have screened the sera from thirty-seven patients with SCLE for the presence of fluorescent antinuclear antibodies (FANA) on two different substrates--human Hep-2 tissue culture cells and mouse kidney sections. In addition, these same sera were assayed for anti-Ro/SS-A precipitin antibodies. Seventy-eight percent of the sera were FANA-positive at a titer of 1:10 or greater when tested on human Hep-2 cells, whereas 76% were positive at a titer of 1:80 or greater. Fifty-one percent were positive on mouse kidney sections at a titer of 1:10 or greater, whereas 46% were positive at a titer of 1:20 or greater. Twenty-two percent of these sera were completely FANA-negative on both human and mouse substrates. None of these sera that were negative on both substrates contained anti-Ro/SS-A antibodies. However, 69% of the sera that were FANA-positive on both human and mouse substrates were found to have detectable anti-Ro/SS-A antibodies. Ninety percent of the SCLE sera that were FANA-positive on human Hep-2 cells, but negative on mouse kidney sections, contained anti-Ro/SS-A antibodies. These sera gave a speckle-like, or particulate, nuclear immunofluorescence staining pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Farmer's lung serologies. An early manifestation of acute histoplasmosis

Three cases of acute histoplasmosis demonstrated, in addition to the usual serologic findings, strongly positive precipitins against farmer's lung antigens. Twelve additional serums from patients with acute histoplasmosis were subsequently studied. Forty percent of these patients demonstrated positive precipitins against organic dust antigens.

Anti-La/SSB antibody is present in some normal sera and is coincident with anti-Ro/SSA precipitins in systemic lupus erythematosus

Sera from 42 patients with systemic lupus erythematosus (SLE) and precipitating antibody to the La/SSB antigen contained 80,000 to 28,800,000 times the minimum detectable binding activity (units) in a solid phase ELISA assay using purified La/SSB antigen. Three normal sera (of 40 tested) had 7,200,21,600 and 21,100 units, respectively, while the log average of the 40 normals was 270 units. Binding activity in normal sera was in the F(ab')2 fragments of IgG, inhibited by purified La/SSB antigen, and bound the major La/SSB peptides. The average apparent relative binding affinity to La/SSB in normal donors was 10-fold lower than in SLE patients with anti-La/SSB precipitins. Analysis of other SLE sera revealed a high incidence of anti-La/SSB in association with anti-Ro/SSA precipitins.

Tobacco smoke "sensitivity"--is there an immunologic basis?

This study was undertaken to determine if there is an immunologic basis for reported tobacco-smoke hypersensitivity in man. Ninety-three individuals who were recruited on the basis of their smoking history and/or claimed sensitivity to tobacco smoke were skin prick tested with tobacco smoke and leaf extracts and their sera analyzed for reaginic and precipitating antibodies to these antigens. Results demonstrated that a significant number of the individuals who were tested had positive skin test and RAST responses to tobacco leaf antigens, whereas only a small number responded to smoke antigens. RAST or skin test responses of study subjects to leaf or smoke antigens did not correlate with symptoms of tobacco-smoke "sensitivity" or smoking history but did correlate with atopic status. Precipitins were detected only to tobacco leaf C in 46 of the 93 individuals who were tested but did not correlate with smoking history or smoke "sensitivity." These results suggest that subjective tobacco-smoke sensitivity is not caused by hypersensitivity to tobacco leaf or smoke antigens.

A precipitin for human serum proteins as released under stress by a marine invertebrate, the marsh snail, Littorina irrorata

A substance released into the environment by stressed marsh snails, Littorina irrorata, precipitates with the beta globulin and albumin fractions of human serum proteins. Other diverse invertebrate species may produce a similar substance. Invertebrate precipitins have not been widely reported, and none like the one described. Some physicochemical and adaptive characteristics of the snail precipitin are presented. This precipitin can be produced in large quantities and has potential application as a diagnostic reagent.

Hypersensitivity pneumonitis--pathology and pathogenesis

Early reports of hypersensitivity pneumonitis postulated that the disease was infectious or resulted from the toxic properties of the inhaled organic dusts. The finding of precipitating antibodies to moldy hay in farmers afflicted with farmer's lung suggested a role for antibody in pathogenesis, and a type III (antigen-antibody complex-mediated or Arthus) hypersensitivity reaction based on the classification of allergic reactions by Gell and Coombs was postulated. Subsequent studies have indicated the importance of cell-mediated (delayed) hypersensitivity (type IV). It must be recognized that hypersensitivity mechanisms are quite complicated and that the classification of Gell and Coombs is an oversimplification; interreacting humoral and cellular responses are typical of most hypersensitivity reactions of whatever classic type as originally defined. The prime importance of T-cell- and macrophage-mediated inflammation in HP, however, is indicated by histopathology, animal models, and in vitro correlates in humans. Major difficulties in defining completely the exact effector mechanisms involved in the pathogenesis of HP include the absence of a reliable in vitro correlate of antigen-specific effector T cells (the so called TDH cell) and the overwhelming versatility of the macrophage. There is no direct evidence to support contributions by precipitins, complement, or genetic host factors in the pathogenesis of hypersensitivity pneumonitis, nor are there studies as yet of cellular cytotoxicity contributions. Cellular and antibody interactions may lead to immunosuppressive processes modulating inflammatory responses and preventing disease despite immunogenesis. Animal models are helpful in dissecting mechanisms and defining effector functions. The eventual goal in studies of pathogenesis is to provide better tools for definitive diagnosis and methods of disease prevention, modulation, and cure.

Grouping of haemolytic streptococci by monoclonal antibodies: determinant specificity, cross-reactivity and affinity

Streptococcal group polysaccharide (CHO), A-, A-variant-, B-, C-, D- and G-specific monoclonal antibodies were prepared by the hybridoma technique employing spleen cells of several inbred mouse strains which are either high or low responders to the group A-CHO. The isotypes of these reagents were restricted to the class mu and IgG subclasses gamma 3 and--in small numbers--gamma 1. Two distinct categories of antibodies were identified for all but group D specificity: those which agglutinate suspended bacteria but do not precipitate purified soluble antigen, and those which show both agglutinating and precipitating properties. The group D antibodies described here were only of the latter category. The reactions were inhibitable by haptens in as far as these were known. Cross-reactions were observed in group-A-specific antibodies with E and L polysaccharides. Most G-CHO-specific antibodies cross-reacted with B-CHO. Association constants determined by fluorescence quenching measurements were for binding of complete A and C polysaccharides in the range of 10(6) to greater than 10(8) M-1, and for hapten binding by A-, Av- and C-CHO-specific antibodies in the range of 10(3) to 10(4) M-1. These results support a model of steric arrangements of antigenic determinants on A-variant bacteria and solubilized antigen [42] and allow its extension to streptococcal groups A, B, C and G. This model explains the observed functional differences by postulating single, terminal determinants which interact with the prevailing non-precipitating antibodies and internal repeating determinants which react with precipitins, respectively. No significant differences were found in the reactivity patterns to these streptococcal group antigens between strains of mice in terms of their ability to respond with high or low serum antibody titres to group A-CHO. On the other hand, within high and low responder strains, different kinetics of the optimal timing of fusion after initiation of the secondary immune reaction by boosting was observed. Low responders were most efficiently used for fusion 1.5 days later than high-responder spleen cells. This feature is interpreted to indicate an earlier proliferation of B lymphocytes in high responders, due to either an improved responsiveness to T-lymphocyte help or a reduced reactivity with T suppressor cells in comparison to low-responder B lymphocytes.