Lymphocyte activation after exposure to swine dust: a role of humoral mediators and phagocytic cells.

Exposure to swine dust causes intense airway inflammation with multifold increase in inflammatory cells and secretion of pro-inflammatory cytokines. This in vitro study focuses on the swine-dust activation of lymphocytes in whole blood, in phagocyte-depleted whole blood and in peripheral blood mononuclear cells (PBMC), in order to investigate whether phagocytic cells and/or soluble mediators are involved in the activation of T-cells following exposure to organic dust from a swine confinement house. T-cell activation was analysed by flow cytometry with double staining for CD3 and the activation marker CD69. Swine dust (50 microg) incubated (24 h) with heparinized whole blood was shown to activate 27.6% of the T-cells, while swine dust incubated with whole blood depleted from phagocytic cells or PBMC only activated 4.5%, and 4.8% of the T-cells, respectively. Plasma separated from whole blood preincubated with swine dust for 24 h stimulated as much as 32.4% of PBMC T-cells and contained high levels of interleukin (IL)-12 (14 pg x mL) and interferon (IFN)-gamma (2284 pg x mL(-1)), while plasma from PBMC incubated with swine dust contained low levels of IL-12 (2 pg x mL(-1)) and IFN-gamma (196 pg x mL(-1)). This study demonstrates that activation of T-cells by organic dust from a swine confinement building seems to require phagocytic cells, most likely acting through the release of soluble mediators. Also, conditioned plasma from swine-dust exposed whole blood, which was capable of activating T-cells, contained high concentrations of interleukin-12 and interferon-y.

Working with male rodents may increase risk of allergy to laboratory animals.

BACKGROUND: Our aim was to study the risk of laboratory animal allergy (LAA) among research staff working in laboratories separate from the animal confinement area. The roles of atopy and exposure intensity in LAA were studied with special regard to exposure to male rodents, who excrete higher levels of urinary allergens than female rodents. METHODS: Eighty rodent-exposed subjects gave blood samples for the analysis of total IgE, Phadiatop, and specific IgE against rat (RUA) and mouse urinary allergens (MUA), and answered questionnaires. Air samples were collected for RUA and MUA aeroallergen measurement in both laboratories and animal confinement facilities. RESULTS: Twenty percent of the subjects had IgE >0.35 kU/l to RUA and/or MUA, and 32% had experienced animal work-related symptoms, although 90% of aeroallergen samples from the research department laboratories were below the detection limit (<0.26 ng RUA per m(3) and <0.8 ng MUA per m(3)). Atopy (positive Phadiatop), total IgE >100 kU/l, other allergies (especially to other animals), or more than 4 years of exposure significantly increased laboratory animal sensitization and symptoms. Working with mainly male rodents gave odds ratios (95% CI) of 3.8 (0.97-15) for sensitization and 4.4 (1.4-14) for symptoms. Subjects with both exposure to mainly male rodents and atopy or elevated total IgE had a 10-fold higher frequency of sensitization than exposed subjects with neither risk factor. CONCLUSION: A majority of subjects with a combination of exposure to mainly male rodents and atopy or elevated total IgE developed sensitization to and symptoms from laboratory animals. Current low exposure seems to maintain the presence of specific IgE. Further measures must be undertaken to provide a safe workplace for laboratory animal workers.

Dispersion of horse allergen in the ambient air, detected with sandwich ELISA.

BACKGROUND: The objective was to establish an ELISA to detect horse allergen in ambient air and settled dust. METHODS: Monoclonal antibodies (mAbs) were produced against extracts of horse antigen. Two mAbs were selected and used in a sandwich ELISA. By the aid of portable pumps, air samples were collected in one stable and in the ambient air surrounding this stable. Furthermore, settled dust was collected by wiping spots with pieces of fabric, at sites within 500 m of the stable. RESULTS: Extracts of horsehair could be extensively diluted and still be positive. Extracts of cat and dog allergen failed to be detected. Furthermore, the mAbs were shown to detect an IgE-binding component. This was demonstrated by an ELISA using mAbs as capture antibody and sera from horse-allergic subjects as secondary antibody with readout depending on anti-IgE antibody. The sera with the highest RAST class to horse were positive in this ELISA. Airborne levels of horse allergen were over 500-fold higher in the stable than just outside the stable and over 3000-fold higher than at a residential building located only 12 m from the stable. Similarly, an inverse correlation was found between the distance to the stable and levels of "outdoor settled" horse allergen (r=-0.9, P<0.001). CONCLUSION: We have developed a sensitive, horse-allergen-specific, mAb assay allowing detection of low levels of horse allergens. Raised levels of horse allergen were found outdoors only in the close vicinity of the stable.

T-cell activation by organic dust in vitro.

Inhalation of swine dust causes intense airway inflammation with a multifold increase of inflammatory cells and lymphocyte activation as assessed by bronchoalveolar lavage. To further investigate the mechanism for lymphocyte activation the present in vitro study focuses on the lymphocyte response to swine dust in whole blood. Various concentrations of phytohaemagglutinin (PHA) (final concentrations: 3.16, 10.0, 3.16 and 100 microg ml(-1)) and swine dust (final concentrations: 10.0, 31.6, 100 and 316 microg ml(-1)) were added to heparinized whole blood from healthy donors. The blood samples were incubated in duplicate, using the homologous unstimulated blood as control, for 4, 24, 48 and 72 h in a water bath at 37 degrees C. The cells were stained with fluorochrome conjugated monoclonal antibodies. For analysis of T-cell activation CD3 was double-stained together with the activation markers CD69, CD25 and HLADR. Cell count percentages were analysed by flow cytometry. Soluble IL-2sRalpha in plasma was analysed using commercial sandwich ELISA technique. At baseline CD69, CD25 and HLA-DR were expressed in < 1%, approx 5% and < 1% of the T-cells respectively. We found a dose response relationship between swine dust exposure and the expression of all three T-cell activation markers which appeared at different time-points. Maximal expression of CD69 (8%, P<0.05) and CD25 (15%, P<0.001) was found after 24h of activation. HLA-DR was significantly expressed after 48h (8%) and maximally expressed after 72 h of activation (13%, P<0.05). The soluble IL-2sRalpha in plasma was maximally expressed after 24-48 h (1200 pg ml(1) and 1500 pg ml(-1), respectively. In conclusion, T-cells were activated by swine dust in vitro. Thus, our previous findings of T-cell activation following swine dust exposure, in vivo may be an effect of the dust either directly on T-cells or on other cells which in turn contribute to the T-cell activation.

School as a risk environment for children allergic to cats and a site for transfer of cat allergen to homes.

BACKGROUND: Many children are allergic to furred pets and avoid direct pet contact. The school may be a site of indirect exposure to pet allergens, which may induce or maintain symptoms of allergic diseases. OBJECTIVE: We sought to investigate airborne levels of cat allergen (Fel d 1) at schools and in homes with or without cats and to study clothes as a route for dissemination of allergens between homes and school. METHODS: Airborne cat allergen was collected with personal samplers from (1) children attending classes with many (>25%) or few (<10%) cat owners and (2) homes with or without cats. A recently developed amplified ELISA assay, which detects low levels of airborne cat allergen in pet-free environments, was used. Dust samples were collected from clothes and mattresses. RESULTS: There was a 5-fold difference in the median levels of airborne cat allergen between classes with many and few cat owners (2.94 vs 0.59 ng/m3; P <.001). The median airborne cat allergen concentration in classes with many cat owners was significantly higher than that found in the homes of non-cat owners (P <.001) but lower than that found in homes with cats (P <.001). Allergen levels in non-cat owners' clothes increased after a school day (P <.001). Non-cat owners in classes with many cat owners had higher levels of mattress-bound cat allergen (P =.01). CONCLUSION: The results indicate significant exposure to cat allergen at school. Allergen is spread through clothing from homes with cats to classrooms. There the allergen is dispersed in air and contaminates the clothes of children without cats. The allergen levels in non-cat owners' homes correlate with exposure to cat allergen at school.

Comparison of methods to assess airborne rat and mouse allergen levels. I. Analysis of air samples.

Airborne laboratory-animal allergens can be measured by several methods, but little is known about the effects of important differences in methodology. Therefore, methods used in research projects in The Netherlands, the UK, and Sweden were compared. Seventy-four sets of three parallel inhalable dust samples were taken by a single operator in animal facilities in the three countries, and analyzed in parallel by the three institutes for rat and mouse urinary allergen. Rat-allergen levels measured by RAST inhibition (UK) were 3000 and 1700 times higher than levels measured by enzyme immunoassay (EIA)-sandwich methods with polyclonal rabbit (The Netherlands) or monoclonal mouse (Sweden) antibodies, while the difference between the two EIA-sandwich methods was much smaller: a factor of 2.2. For mouse allergen, an inhibition radioimmunoassay (RIA) with rabbit antimouse antibodies (UK) gave 4.6 and 5.9 times higher concentrations than sandwich EIAs with rabbit polyclonal antibodies (Sweden and The Netherlands), while the difference between the two sandwich EIAs was, on average, 1.6-fold. Thus, although levels of rat and mouse aeroallergens are significantly correlated, the assay type gives large differences in absolute concentrations, and interlaboratory technical differences affect even the same assay type. Conversion factors can aid comparison between studies, and, in the long term, assay standardization is desirable.

Comparison of methods to assess airborne rat and mouse allergen levels. II. Factors influencing antigen detection.

Potential factors influencing antigen detection in immunoassays for measuring rat or mouse aeroallergen (i.e., assay setup, antigen specificities, standard extracts used, and antigen decay) were investigated in a three-country study (the UK, The Netherlands, Sweden). An inhibition enzyme immunoassay (EIA) setup gave nominal rat urinary allergen (RUA) sample values seven times higher than a sandwich EIA setup utilizing identical antibodies and standards. In immunoblotting experiments, pooled patient serum and polyclonal rabbit antibodies partly detected different rat antigens; monoclonal antibody specificity could not be determined. Immunoblot detection of mouse urinary antigens (MUA) by the polyclonal rabbit antibodies from all laboratories was similar. In both the RUA and the MUA assays, urinary antigen standards were detected with similar potency, except purified Rat n 1, which was an inefficient inhibitor in the RUA RAST inhibition. In the sandwich EIA RUA assays, a rat room-dust extract was detected with 700800-fold less sensitivity than rat urine, whereas in the RAST RUA assay, dust inhibited equally with rat urine. Simulated decay did not decrease the potency of urinary antigen in any assay. Thus, assay setup and choice of detection antibodies strongly influence the nominal allergen levels. We recommend the use of standardized and characterized antibodies and standard extracts in sandwich EIAs to measure airborne rodent urinary allergens.

Increase in interleukin-6 and fibrinogen in peripheral blood after swine dust inhalation.

OBJECTIVES: The inhalation of dust from swine confinement buildings causes inflammatory responses in the airways with a rise of interleukin-6 (IL-6). The purpose of this study was to confirm the increase in serum IL-6 after inhalation of swine dust and investigate a possible increase in plasma fibrinogen. METHODS: Eight healthy nonsmoking volunteers inhaled dust for 4 hours inside a swine confinement building. Inhalable dust and endotoxin were sampled. The concentrations of IL-6 and fibrinogen were determined in serum and plasma. RESULTS: The study showed a clear increase in the concentrations of IL-6 and fibrinogen after exposure. CONCLUSIONS: As fibrinogen is an important risk factor for ischemic heart disease, the increased concentration of fibrinogen among persons exposed to swine dust may increase the risk for this disease.

Budesonide but not terbutaline decreases phagocytosis in alveolar macrophages.

Alveolar macrophages are the most common cells in bronchoalveolar lavage fluid. The macrophages participate in the inflammatory response and defence of the airways by secretion of mediators and by phagocytizing foreign particles such as bacteria and viruses. beta-Agonists and glucocorticosteroids are the most frequently used drugs in asthma. Alveolar macrophages have beta 2-adrenoceptors on their surface but the functional role of these receptors is unknown. Glucocorticosteroids interact with mediator release from macrophages. However, nothing is known about the effects of those drugs on the phagocytic capacity of alveolar macrophages. Therefore, the present study has investigated phagocytosis of alveolar macrophages from nine healthy volunteers after incubation with a beta 2-agonist, terbutaline (10(-8), 10(-6) and 10(-4) M) and a glucocorticosteroid, budesonide (10(-9), 10(-7) and 10(-5) M). Alveolar macrophages were incubated with FITC-labelled Escherichia coli, and the drugs and phagocytosis was assessed by flow cytometry. Phagocytosis was measured as the proportion of phagocytizing cells and mean fluorescence intensity (MFI). MFI was highly correlated with phagocytized E. coli per cell assessed by fluorescence microscopy (r = 0.996). The proportion of phagocytizing macrophages (control) was [median (25th-75th) percentiles] 46% (40-63) and 29% (18-60), and MFI were 174 (154-205) and 122 (90-271) in the terbutaline and budesonide experiments, respectively. Terbutaline did not affect the phagocytosis significantly, while budesonide decreased the phagocytic capacity (percent phagocytizing cells and MFI) in a dose-dependent manner (P < 0.01). At the highest budesonide concentration (10(-5) M), phagocytosis was approximately half of the control situation. In conclusion, this in vitro study indicate that a glucocorticosteroid decreases phagocytosis in alveolar macrophages in a concentration that may be relevant in the airway lining fluid. Further investigations regarding the effect on other micro-organisms and in vivo effects are necessary to further elucidate these findings.

Free radicals as potential mediators of metal allergy: effect of ascorbic acid on lymphocyte proliferation and IFN-gamma production in contact allergy to Ni2+ and Co2+.

A possible free radical mechanism in metal allergy was investigated in peripheral blood mononuclear cell (PBMC) cultures from 6 subjects, contact allergic to Ni2+ and Co2+, and 6 control individuals. Ni2+ and Co(2+)-mediated free radical generation was studied with electron spin resonance spectroscopy. The immune response was characterized by cellular [methyl-3H]thymidine uptake and interferon-gamma (IFN-gamma) production Ni2+ and Co2+ (10-50 microM) significantly increased lymphocyte proliferation and IFN-gamma production in PBMC cultures from contact allergic subjects in comparison with cultures from controls. Inhibition of Co(2+)-mediated free radical generation by ascorbic acid did not influence cellular [methyl-3H]thymidine uptake and IFN production. Detectable amounts of free radicals were not obtained with Ni2+. We therefore conclude that it is unlikely that free radicals are involved in contact allergy to Ni2+ and Co2+.

A new amplified monoclonal rat allergen assay used for evaluation of ventilation improvements in animal rooms.

BACKGROUND: Available methods for the measurement of airborne laboratory animal allergens are not standardized and are often insufficiently sensitive for measurements in laboratories or in undisturbed animal rooms. Although low, the levels may be clinically relevant, because many scientists not involved in cleaning out cages or handling animals have rodent allergies. OBJECTIVE: The purpose of this study was to develop a sensitive monoclonal assay to determine airborne rat allergen and test it in the evaluation of a sliding curtain system installed in refurbished rat rooms, with perforated, transparent polycarbonate screens, behind which were the cage racks. METHODS: Monoclonal antibodies were produced against male rat urine by immunization in mice and fusion with mouse cell line Sp2/0. A novel biotinylated phenol compound was synthesized for immunoassay signal amplification in conjunction with horseradish peroxidase. Air filter samples were collected at a rate of 2 L/min, and allergen content in the filter eluates was determined. RESULTS: Two monoclonal antibodies were produced and used in a sandwich ELISA, which bound alpha2u-globulin (Rat n 1.02). The assay detection limit was 3.2 pg/ml, about tenfold increased sensitivity compared with the unamplified assay. Allergen levels were lower in rooms when curtains were closed (median, 0.2 ng/m3) than behind the curtains (0.9 ng/m3, p = 0.01) or if the curtains were open (0.9 ng/m3, p = 0.001). However, allergen levels during cage cleaning, when curtains were drawn apart, were high (18 ng/m3). CONCLUSION: We have developed a method for measurement of airborne rat allergen that can be standardized, measures an important allergen, and is sufficiently sensitive to measure low allergen levels with personal samplers.

Increased number of activated lymphocytes in human lung following swine dust inhalation.

Inhalation of swine dust causes intense alveolar inflammation, with recruitment of inflammatory cells, predominantly neutrophils, but also alveolar macrophages and lymphocytes. The present study focuses on the lymphocyte response to inhaled swine dust. Twenty four healthy, nonsmoking, nonallergic subjects were exposed to swine dust for 3 h in a swine confinement building. Bronchoalveolar lavage (BAL) was performed before and 24 h after the start of exposure, and blood samples were drawn before, and at 7 and 24 h after exposure. Total and differential cell counts were carried out. Monoclonal antibodies recognizing T-cells, T-cell subsets, T-cell activation markers, and B-cells were analysed by flow cytometry. The number of granulocytes increased more than 50 times and alveolar macrophages and lymphocytes increased two- to three-fold in BAL fluid. The exposure did not alter the proportion of T-cells but increased the number of activated T-cells in BAL fluid. The interleukin-2 (IL-2) receptor (CD25), human leucocyte antigen-DR (HLA-DR) major histocompatibility complex (MHC) class II and the early activation marker CD69 were expressed by 8.4% (25-75th percentiles 6.4-9.6%), 9.9% (8.2-21.6%) and 22.0% (18.1-24.3%) of the lymphocytes prior to exposure, and 11.6% (9.0-16.4%) (p < 0.01), 18.8% (12.9-30.4%) (p < 0.01) and 42.1% (38.4-47.3%) (p < 0.05), respectively, after the exposure. In peripheral blood, the concentration of T-cells decreased after exposure and B-cells increased slightly but significantly. The ratio naive/memory T-cells (CD45RA/RO) did not change in blood. In conclusion, 3 h of swine dust inhalation led to an influx of lymphocytes into the lower airways and increased expression of lymphocyte activation markers on the cell surface in previously unexposed subjects. The finding suggests a role for T-cells, in conjunction with other cells, in the inflammatory response to inhaled swine dust.

Covalent binding of proteins to grafted plastic surfaces suitable for immunoassays. II. Picograms of IgE detected in BAL fluid in sarcoidosis.

An ELISA is described for the quantitation of minute amounts of human IgE using microtiter strips which were surface modified according to a procedure previously described. This ELISA used an IgG fraction of a rabbit polyclonal anti-IgE antibody coupled to the carboxylated surface, which prior to coupling had been preactivated with a water soluble carbodiimide. A biotinylated affinity purified rabbit anti-IgE antibody was used together with streptavidin conjugated alkaline phosphatase and biotinylated enzyme for the detection of bound analyte. Sarcoidosis is a systemic disorder of as yet unknown cause with epithelioid granuloma formation in the lung as a prominent feature. With the bronchoalveolar lavage technique, epithelial lining fluid was obtained and analyzed for IgE content since differences of immunoglobulin concentration in bronchoalveolar lavage fluid (BALF) may reflect disease activity. Our modified ELISA system was used for measuring IgE in BALF from healthy controls and sarcoid patients. The assay using modified strips demonstrated a considerably improved sensitivity compared to the use of physical adsorption of first antibody to untreated strips. The detection limit of the improved assay was approximately 3 pg IgE/sample (100 microl). Quantitative recovery of IgE was demonstrated within the measuring range (51.2-12500 pg IgE/ml) and more than 40% (23/54) of the sarcoid patients showed values above the lowest standard concentration (51.2 pg/ml). In contrast, none of the healthy controls (0/22) had detectable IgE as defined by the detection limit of the assay.

Comparison of a radioallergosorbent (RAST) inhibition method and a monoclonal enzyme linked immunosorbent assay (ELISA) for aeroallergen measurement.

BACKGROUND: Mouse and rat urinary proteins are potent occupational allergens for exposed personnel. Methods of measuring airborne allergens differ greatly, and reported levels of allergens vary considerably between laboratories. OBJECTIVES: To compare the values obtained using two different methods of allergen detection. METHODS: Air samples were collected in rat rooms in Sweden and the United Kingdom at 2 L/min on to polytetrafluoroethylene (PTFE) filters and extracted in buffer containing 0.5% v/v Tween 20. Airborne rat urinary allergen (RUA) was measured in all samples by both RAST inhibition using a polyclonal human serum pool (UK) and a two monoclonal antibody sandwich ELISA employing antibodies specific for Rat n 1.02 (alpha2u-globulin) (Sweden). RESULTS: The two methods gave values which were correlated (r2 log values = 0.72, P<0.0001), but differed by several orders of magnitude (median [range] ratio of RAST inhibition/ELISA = 316 [7-26(80)]. There was a systematic bias: as the absolute values increased, the difference in the measurements increased. The rat urine standards used were antigenically similar. CONCLUSIONS: A large contrast in RUA values obtained from the two assays was observed in this study. This may be primarily due to methodological differences, but variations in antibody specificities or composition of allergenic epitopes in the air samples may contribute. The results demonstrate that standardization of methods and antibodies is necessary before interlaboratory comparisons can be made.

Allergic sensitization is associated with increased bronchial responsiveness: a prospective study of allergy to laboratory animals.

The purpose of this prospective study was to investigate the extent of change in bronchial responsiveness and the prognostic value of methacholine provocation in early sensitization to laboratory animals. Thirty eight laboratory technicians were studied during training (before first exposure) and after having been exposed to laboratory animals for a median 18 (range 5-33) months. On both occasions they were subjected to spirometry, bronchial methacholine challenge, skin-prick tests and blood sampling, and responded to questionnaires. Nine (24%) developed laboratory animal allergy (LAA), defined as animal work-related symptoms (n = 8), or specific immunoglobulin E (IgE) (n = 7) or both. In the LAA group, bronchial responsiveness was normal before employment, but had increased significantly at follow-up compared to technicians who had not developed LAA. Six of the nine LAA subjects had a more than threefold increase in bronchial responsiveness, and three of these reported chest symptoms. Spirometric values were not different between the groups prior to exposure or at follow-up, and had no prognostic value. However, a pre-employment level of total IgE > 100 kU.L-1 predicted the development of LAA (relative risk 2.8). Thus, early LAA was associated with increased bronchial responsiveness in most subjects. In contrast to total IgE, the level of pre-employment bronchial responsiveness or lung function did not influence the magnitude of change in responsiveness, nor predict sensitization.

Prospective study of laboratory-animal allergy: factors predisposing to sensitization and development of allergic symptoms.

In a prospective study of laboratory technicians, selected indicators of allergy and atopy were studied in an attempt to determine predictors of laboratory-animal allergy (LAA). Laboratory technicians underwent spirometry, methacholine provocation tests, and blood sampling, and responded to a questionnaire during training and after 2 years' work. Among 38 laboratory-animal-exposed subjects, total IgE before exposure gave the best correlation (P < 0.01; Mann-Whitney U-test) to reported symptoms caused by laboratory animals (n = 8) at follow-up. The prevalence of atopy and allergic symptoms had increased in exposed technicians at follow-up, but this was also found among unexposed matched referents (n = 36 pairs). One subject in the exposed group reported asthma before exposure, compared with seven at follow-up (P < 0.05; Fisher's exact test). However, the prevalence of asthma had increased from two to six (not significant) also among unexposed technicians. There were no significant differences between the groups in any measured variable at follow-up. Among 43 subjects who later worked with laboratory animals, 21% had a positive skin prick test for common allergens, as compared with 37% among 112 without animal exposure (P = 0.06; chi2 test), suggesting selection for laboratory animal work.

IgE elevation and IgE anti-malarial antibodies in Plasmodium falciparum malaria: association of high IgE levels with cerebral malaria.

In the course of studying immunoregulation in human Plasmodium falciparum malaria we have investigated IgE levels and IgE anti-plasmodial antibodies in children and adults from areas of high malaria endemicity in both Africa and Asia. On average, 85% of all donors had significantly elevated levels of total IgE. A fraction of the IgE had anti-plasmodial activity as revealed by ELISA with lysates of infected erythrocytes as antigen. Using synthetic peptides representing antigenic regions of two major plasmodial blood stage antigens, IgE antibody concentrations ranged from 5 to 15 ng/ml serum for each of the peptides. On average, the concentrations of the corresponding IgG antibodies were x 500-1000 higher. Immunoblotting of parasite lysates showed that most donors had IgE antibodies against one or several of a restricted number of plasmodial polypeptides, with antibodies against an antigen of mol.wt 45 kD already being present in all donors at an early age. Donors having IgE antibodies to particular antigens also frequently had corresponding IgG4 antibodies, reflecting underlying IL-4-dependent cellular mechanisms controlling formation of these isotypes. As infection with other parasites such as helminths is known to induce IgE elevation, the results do not prove that plasmodial infections were the primary cause of IgE induction. However, the importance of plasmodial infection for IgE elevation was supported by the finding of significantly higher levels of IgE, but not of IgG, in children with cerebral malaria compared with patients with uncomplicated disease.

Serum reactivity to other indoor ficus plants in patients with allergy to weeping fig (Ficus benjamina).

Ornamental plants have long been used for indoor decoration. An example is the india rubber tree (Ficus elastica). With the increased popularity of green plants, both in private homes and public premises, small-leaf species, such as weeping fig or Ficus benjamina (Fb), have become widely used. Exposure to dust from Fb may cause sensitization and allergic airway symptoms, which among occupationally exposed plant keepers occur both in atopics and non-atopics. The serum reactivity to sap extracts from Fb and seven other indoor plants of the genus Ficus were investigated with RAST and a RAST inhibition technique, using sera from 12 atopic subjects and 12 plant keepers, sensitized to Fb. The allergenic similarity between the different extracts was found to be extensive. The specific IgE antibodies with the highest concentrations in serum were those against Fb and its variegate form, "star light", with decreasing values for the other species, especially those with larger leaves. The binding of IgE antibodies to the other Ficus RAST discs could be completely inhibited by extract of Fb. These reactions were probably due to cross-reactivity. Sensitization is believed to occur by inhalation of allergen-enriched dust, emanating from the leaves of the plants. The high allergenic potency of the species with many small leaves may be due to their large total leaf area.

Characterization of allergenic components in sap extract from the weeping fig (Ficus benjamina).

The allergen composition of crude extract from sap (latex) of the weeping fig (Ficus benjamina) was investigated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. The allergenic components were detected by sera from 11 occupationally exposed plant keepers, of whom 7 were non-atopic, and from 9 non-occupationally exposed atopic patients with a positive radio-allergosorbent test to weeping fig. The allergen-antibody complexes were visualized by rabbit anti-IgE and beta-galactosidase-labelled sheep anti-rabbit IgG, using a chromogenic insoluble substrate. A total of 11 allergenic components were identified. Three of them were found to be major allergenic components, identified by more than 50% of the investigated sera. These 3 IgE-binding components had molecular weights of approximately 29,000, 28,000 and 25,000 daltons, respectively. The major allergenic components were denatured by heat in the temperature range of 60-90 degrees C.

Detection of cell-free human immunodeficiency virus in cerebrospinal fluid by using immune scanning electron microscopy.

The cerebrospinal fluid of 52 patients with human immunodeficiency virus type 1 (HIV-1) infection was incubated with polystyrene microspheres coated with monoclonal antibodies specific for HIV-1 core or envelope antigens. The beads were then collected on a filter surface and inspected by scanning electron microscopy (SEM). In 37 of 51 samples from subjects with chronic HIV-1 infection and from all three patients with primary HIV-1 infection, with or without neurologic symptoms, particles of 50-75 nm and 100-125 nm were visualized on beads coated with antibodies to HIV-1 core and envelope antigens, respectively. No such binding of particles was detected in the controls. Findings using immune SEM, which was found to be as sensitive as virus isolation, indicate that HIV-1 can replicate in the central nervous system (CNS) of patients with primary or chronic HIV-1 infection without causing neurologic symptoms. Production of cell-free virus seems to occur in the CNS of the majority of HIV-1-infected patients.