Sensitive amplification immunoassay for human IgG and anti-human IgG by using an enzyme cascade system

A sensitive heterogeneous immunoassay for human IgG and anti-human IgG was developed using an enzyme cascade system in limulus amoebocyte as a signal amplification system. Lipopolysaccharide (LPS) was conjugated to human IgG and anti-human IgG was adsorbed on polystyrene beads. The LPS-labelled human IgG mixed with unlabelled human IgG was allowed to react in a competitive manner with the immobilized anti-IgG on the polystyrene bead surface. After B/F separation, the LPS activity in the supernatant (free) and LPS activity on the bead (bound) were measured by using the chromogenic limulus test. IgG could be measured in the range 10^?7-10^?11 g ml^?1. LPS-labelled anti-IgG and IgG absorbed on polystyrene beads were prepared, and LPS-labeled anti-IgG mixed with unlabelled anti-IgG was allowed to react again in a competitive manner with solid-phase IgG. The LPS activity specifically bound to the bead was then measured. Anti-IgG could be measured in the range 10^?7-10^?11 g ml^?1.     

Protein immobilization on surface modified latices bearing aldehyde groups

A new method for providing polymeric microspheres with aldehyde functional groups capable of covalent reaction with proteins is described. Benzyl halide groups on small molecules, polymeric resins, and the surfaces of surfactant-free poly(styrene-co-chloromethylstyrene) were converted to benzaldehyde groups by oxidation with 2-nitropropane in aqueous sodium methoxide. The modified microspheres containing aldehyde groups can be reacted with protein under milder conditions than the parent microspheres. The activity of a monoclonal antibody, Phe 1.9, was higher when it was immobilized on the aldehyde-containing beads than following immobilization on the parent beads.     

Covalently Bound Antibody on Polystyrene Latex Beads: Formation, Stability, and Use in Analyses of White Blood Cell Populations

CD4 or CD8 antibodies were covalently bound to latex beads by reaction of activated CD4 or CD8 monoclonal antibodies with 2-μm-diameter, 1,3-diaminopropane (DAP) coupled, polystyrene aldehyde/sulfate latex beads. Spectrophotometric analyses of the filtrates of the antibody-bead conjugation mixtures for unreacted antibody allowed construction of binding curves of antibody for the polystyrene bead surface and evaluation of binding constants for association of antibody with bead, ranging from 1.5x10(7) to 1.6x10(7) M(-1) for CD4 and CD8 antibodies. The reaction of the antibody thiol group with the activated maleimide group on the bead at pH 7.2-7.3 was complete within 10-15 min. The kinetics of CD4 or CD8 monoclonal antibody displacement from the surface of covalently conjugated antibody-polystyrene latex beads was followed as a function of temperature (5, 22, and 37 degrees C) and the nature of the final diluent for the antibody-coated beads by measuring the concentration of antibody in the filtrates of conjugated beads by an ELISA (enzyme-linked immunosorbent assay). The displacement reaction showed a pseudo-zero-order dependence of the rate, with constants, k(1), ranging from 0.65x10(-17) to 270x10(-17) M s(-1). The functionality of antibody-coated beads suspended in various media was also monitored in a biological cell assay with whole blood. The cell assay depends on forming a layer of beads around targeted lymphocytes to distinguish them from nontargeted lymphocytes by differences in dc or rf conductivity or median angle light scatter. Covalently bound CD4 and CD8 antibody beads stored in one set of media at 5, 22, and 37 degrees C over a period of 16 weeks showed excellent results in the STKS assay with various blood donors, which correlated well (correlation coefficients of 0.99 for CD4 data and 0.93 for CD8 data) with reference results obtained with fluorescent markers by flow cytometry. Covalently bound CD4/CD8 beads stored for 2 weeks in BSA buffer at 5-37 degrees C performed equally well in providing accurate values of the percentage of CD4- or CD8-positive cells in the total white blood cell population, whereas the same beads stored in the 47-50 degrees C range showed some failures in performance. Comparison with antibody concentrations in filtrates of adsorbed antibody-bead suspensions showed 2- to 10-fold greater amounts of free antibody at comparable elapsed time, media, and temperature conditions. A threshold of 1-2 μg/mL of free antibody was necessary before adverse effects on the biological cell assay were noticeable. Copyright 2001 Academic Press.     

Structural and immunochemical analysis of the lipopolysaccharide from Acinetobacter lwoffii F78 located outside Chlamydiaceae with a Chlamydia-specific lipopolysaccharide epitope

Chemical analyses, NMR spectroscopy, and mass spectrometry were used to elucidate the structure of the rough lipopolysaccharide (LPS) isolated from Acinetobacter lwoffii F78. As a prominent feature, the core region of this LPS contained the disaccharide alpha-Kdo-(2-->8)-alpha-Kdo (Kdo=3-deoxy-d-D-manno-oct-2-ulopyranosonic acid), which so far has been identified only in chlamydial LPS. In serological investigations, the anti-chlamydial LPS monoclonal antibody S25-2, which is specific for the epitope alpha-Kdo-(2-->8)-alpha-Kdo, reacted with A. lwoffii F78 LPS. Thus, an LPS was identified outside Chlamydiaceae that contains a Chlamydia-specific LPS epitope in its core region.     

Preparation and structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanocomposite upon intercalating reaction

Poly(ethylene glycol) possessing pentaethylenehexamine at one end (N6-PEG) was prepared via a reductive amination reaction of aldehyde-ended PEG with pentaethylenehexamine. Using N6-PEG, an antibody/PEG co-immobilized surface was constructed on magnetic particles via an active ester reaction method. After immobilization of the antibody on the active ester surface, N6-PEG was reacted on the magnetic beads. A sandwich enzyme-linked immunosorbent assay (ELISA) system was newly constructed using PEG/antibody co-immobilized magnetic beads combined with an alkaline phosphatase (ALP)-assisted fluorescent detection system using alpha-fetoprotein (AFP) as a model antigen. The co-immobilization of both antibody and PEG on the magnetic bead surfaces reduced the nonspecific adsorption of proteins from cell lysates. Especially, when the magnetic particle surface was modified by N6-PEG mixtures with different molecular weights of 6000 and 2500 (6 kDa:2.5 kDa=9:1 w/w), the nonspecific adsorption of proteins was strongly suppressed. It is rather surprising for us that the sensitivity of the antibody on the surface was enhanced significantly when the PEG tethered chain was constructed in between the surface antibodies. Consequently, the mixed N6-PEG treatment showed a much higher S/N ratio than for the corresponding beads treated with bovine serum albumin (BSA), a conventional blocking reagent. Actually, when alpha-fetoprotein was analyzed by the magnetic bead-assisted ELISA thus constructed, the S/N ratio was about 20-fold higher for the mixed coating with PEG (6 kDa):PEG (2.5 kDa)=9:1, compared to the conventional BSA.     

Simultaneous detection of Escherichia coli O157:H7 and Salmonella Typhimurium using quantum dots as fluorescence labels

In this study, we explored the use of semiconductor quantum dots (QDs) as fluorescence labels in immunoassays for simultaneous detection of two species of foodborne pathogenic bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium. QDs with different sizes can be excited with a single wavelength of light, resulting in different emission peaks that can be measured simultaneously. Highly fluorescent semiconductor quantum dots with different emission wavelengths (525 nm and 705 nm) were conjugated to anti-E. coli O157 and anti-Salmonella antibodies, respectively. Target bacteria were separated from samples by using specific antibody coated magnetic beads. The bead-cell complexes reacted with QD-antibody conjugates to form bead-cell-QD complexes. Fluorescent microscopic images of QD labeled E. coli and Salmonella cells demonstrated that QD-antibody conjugates could evenly and completely attach to the surface of bacterial cells, indicating that the conjugated QD molecules still retain their effective fluorescence, while the conjugated antibody molecules remain active and are able to recognize their specific target bacteria in a complex mixture. The intensities of fluorescence emission peaks at 525 nm and 705 nm of the final complexes were measured for quantitative detection of E. coli O157:H7 and S. Typhimurium simultaneously. The fluorescence intensity (FI) as a function of cell number (N) was found for Salmonella and E. coli, respectively. The regression models can be expressed as: FI = 60.6 log N- 250.9 with R(2) = 0.97 for S. Typhimurium, and FI = 77.8 log N- 245.2 with R(2) = 0.91 for E. coli O157:H7 in the range of cell numbers from 10(4) to 10(7) cfu ml(-1). The detection limit of this method was 10(4) cfu ml(-1). The detection could be completed within 2 hours. The principle of this method could be extended to detect multiple species of bacteria (3-4 species) simultaneously, depending on the availability of each type of QD-antibody conjugates with a unique emission peak and the antibody coated magnetic beads specific to each species of bacteria.     

On-column capture of a specific protein separated by SDS-CGE using an immunological reaction on magnetic beads

The on-column capture of a specific protein using magnetic beads was applied to SDS-CGE. In a preliminary study, an immunological reaction in the presence of SDS, using a batch method, was attempted. Carbonic anhydrase (CA), alpha-lactalbumin (LA), and HSA were denatured by heating in the presence of SDS and 2-mercaptoethanol, and then reacted with anti-CA that had been immobilized on magnetic beads. Not only native CA, but also the denatured CA reacted with anti-CA, even in the presence of SDS. Therefore, the on-column capture of denatured CA separated by SDS-CGE was attempted using a two-point detection technique. A mixture of proteins, containing LA, CA, and HSA, were separated by SDS-CGE according to their Mr. The CA was then specifically captured on anti-CA-immobilized magnetic beads, which were packed between two detection windows in the capillary column, during the electrophoresis. The results show that the technique leads to information similar to that obtained by Western blotting, i.e., a protein can be identified by its Mr and reaction with its antibody.     

猪肉中β-受体激动剂AlphaLISA检测方法的建立

建立了快速检测猪肉中克伦特罗、沙丁胺醇、溴布特罗和特布他林4种β-受体激动剂的光激化学发光纳米均相时间分辨荧光免疫(Alpha LISA)分析方法。样品经乙酸铵和β-葡萄糖醛酸酶/硫酸酯酶酶解提取过柱,浓缩至干后,用缓冲溶液定容。样品与生物素化抗原、抗体、供体微珠和受体微珠进行酶联免疫,Alpha LISA进行检测,基质标准曲线定量。结果表明:沙丁胺醇、克伦特罗、溴布特罗和特布他林在0.1~500ng/m L范围内呈良好线性,相关系数均大于0.98,沙丁胺醇与克伦特罗、溴布特罗和特布他林的交叉反应率分别为143.3%,179.2%和95.6%,检出限为0.03~0.08 ng/m L。在0.5,10,20μg/kg 3个添加水平下,4种化合物的平均回收率为82.5%~115.9%,相对标准偏差(RSD)均小于12.0%。该方法操作简单,快速准确,适用于猪肉中β-受体激动剂的筛选与检测。     

超顺磁性免疫磁珠体系用于植物油中黄曲霉毒素B1的检测研究

利用化学共沉淀方法,制得了主要成分为Fe3O4的超顺磁性纳米磁珠。纳米磁珠和硅烷偶联剂氨丙基三乙氧基硅烷(APTES)反应而带上氨基基团。带上氨基的磁珠通过戊二醛活化后发生醛基化,与黄曲霉毒素B1(AFB1)多克隆抗体偶联得到黄曲霉毒素B1免疫磁珠。利用该免疫磁珠为净化工具,建立了有机溶剂萃取、免疫磁珠净化、高效液相色谱(HPLC)检测植物油中黄曲霉毒素B1的方法。该方法具有良好线性,线性范围为5～50μg/L,相关系数达0.999 4,检出限为0.5μg/L,平均回收率为96%,相对标准偏差为12.5%。该方法操作简单、灵敏度高、准确性好,可用于植物油中黄曲霉毒素B1的检测。     

Immunoassay for B. globigii spores as a model for detecting B. anthracis spores in finished water

The 2001 anthrax alarm in the US raised concerns about the Nation's preparedness to the threat of bioterrorism, and the demand for early warning systems that might be used in the case of a biological attack continues to grow. Here we develop an ultra-sensitive rapid detection method for B. globigii(BG) spores, the simulant of B. anthracis(BA) spores. BG spores were detected by a bead-based sandwich immunoassay with fluorescence detection. Paramagnetic Dynal beads were used as a solid support, primary antibody was attached to the beads by streptavidin-biotin coupling and the secondary antibody had an alkaline phosphatase (AP) enzyme label. Enzymatic conversion of fluorescein diphosphate (FDP) to fluorescein by AP was measured in real time with lambda(ex)= 490 nm and lambda(em)= 520 nm. The assay was linear from 2.6 x 10(3)-5.6 x 10(5) BG spores mL(-1), and the detection limit was 2.6 x 10(3) spores mL(-1) or 78 spores. All reagent concentrations and incubation times were optimized. The assay time from the moment the spores were introduced to the system was 30 min, and real-time fluorescence detection was done in less than 1 min. Formation of the BG spores-capture beads complex was confirmed by environmental scanning electron microscopy (ESEM). BG spores were detected successfully when doped into Cincinnati tap water to demonstrate the applicability of the developed method to detect the spores in non-buffered media.     

Sequential injection chemiluminescence immunoassay for anionic surfactants using magnetic microbeads immobilized with an antibody

A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminscence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min.     

Chemiluminescence sequential injection immunoassay for vitellogenin using magnetic microbeads

A rapid and sensitive immunoassay for the determination of carp vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a samarium-cobalt magnet. An anti-Vg monoclonal antibody, immobilized on magnetic beads, was used as a solid support for the immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by a samarium-cobalt magnet and the flow of the carrier solution. The immunoassay was based on a sandwich immunoreaction of anti-Vg monoclonal antibody (primary antibody) on the magnetic beads, Vg, and the anti-Vg antibody labeled with horseradish peroxidase (HRP) (secondary antibody), and was based on a subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The magnetic beads to which the primary antibody was immobilized were prepared by coupling the primary antibody with the magnetic beads after an agarose-layer on the surface of the magnetic beads was epoxidized. The primary antibody-immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the samarium-cobalt magnet, a Vg sample solution, an HRP-labeled secondary antibody solution and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photomultiplier located at the upper side of the flow cell. The optimal incubation times both for the first and second immunoreactions were determined to be 20 min. A concave calibration curve was obtained between Vg concentration and chemiluminescence intensity when various concentrations of standard Vg samples (2–100 ng mL⁻¹) were applied to the SIA system under optimal conditions. In spite of a narrow working range, the lower detection limit of the immunoassay was about 2 ng mL⁻¹.     

Immunoassay for P38 MAPK using surface enhanced resonance Raman spectroscopy (SERRS)

A micro-bead sandwich assay for P38 mitogen-activated protein kinase using surface enhanced resonance Raman spectroscopy (SERRS) detection is reported. Monoclonal capture antibodies were immobilised on a solid phase of magnetic micro-beads with secondary detection using a rhodamine-labelled antibody. Quantitative SERRS detection of the secondary antibody was possible with a limit of detection of 9.5 x 10(-12) mol dm(-3). The sandwich assay was quantitative and sensitive to 6 ng ml(-1). The mechanism of the SERRS detection in the immunoassay was investigated. The addition of SERRS aggregating agents causes the dissociation of the immuno-complex from the magnetic beads. Scanning electron microscopy images indicate that the colloidal suspension rather than adsorbed silver nanoparticles on the beads provide the SERRS signals, that the aggregate size is partially controlled and that there is some inhomogeneity in the distribution of organic matter on the nanoscale.     

Immunoextraction of zinc proteins from human plasma using chicken yolk antibodies immobilized onto paramagnetic particles and their electrophoretic analysis

Zinc(II) as the only transition metal lacking redox activity is an essential part of approximately 10% proteins as a cofactor of these proteins. Considering the fact that there are numerous zinc(II) containing proteins, proteomics and metallomics studies aimed on them require accurate methods for preparation of real biological samples prior to their subsequent analysis using 2DE and MS. For this purpose, we suggested a new method based on chicken anti-zinc antibodies and magnetizable particles. Antibodies were covalently immobilized to the surface of paramagnetic beads activated with tosyl group. Binding of the antibody to the beads was confirmed by secondary anti-chicken antibody conjugated with horseradish peroxidase. The immunoextraction conditions, such as concentration of the beads (6-18 μg/mL of the sample), time of immunoextraction (6-34 min), pH and composition of the elution buffer, and time of extraction (48-300 s) were optimized. Subsequently, zinc proteins were extracted from human plasma and total concentration of zinc was monitored by electrochemical detection in the extracts. Under optimal conditions it was possible to monitor the proteins and zinc removal from the sample by chip CE, SDS-PAGE, and indirectly using electrochemistry.     

稀土铕离子标记抗-乙型肝炎表面抗体

结合生命科学中生物活性物质的高灵敏度分析检测方法研究,组装了时间分辨激光荧光免疫分析装置;合成了稀土离子与蛋白质联接的双向螯合剂－二乙三胺五乙环酐（ＤＴＰＡＡ）;纯化了抗－乙型肝炎表面抗体;研究了Ｅｕ＾３－ＤＴＰＡＡ－抗－乙型肝炎表面抗体制备过程;确定了标记物制备的最佳条件;依据解离增强原理,采用时间分辩激光荧光光谱技术,对Ｅｕ（β－ＮＴＡ）３（ＴＯＰＯ）２螯合物的有关参数进行了测定。     

Effect of nitrite on cell growth and antibody production in mouse splenic B cells stimulated with lipopolysaccharide and B cell hybridomas.

Nitric oxide, nitrite and nitrate are released by activated macrophages in an immune response. We showed here that nitrite influenced cell growth and antibody production in mouse lipopolysaccharide (LPS)-stimulated splenic B cells and B cell hybridomas. The addition of 10(-7) and 10(-6) M nitrite enhanced deoxyribonucleic acid (DNA) synthesis of LPS-stimulated splenic B cells. However, DNA synthesis and antibody production in the case of total spleen cells stimulated with LPS were suppressed by nitrite in a dose dependent-manner. These phenomena were also observed in a similar experiment involving mouse B cell hybridomas. Antibody production of all B cell hybridomas was significantly suppressed by the addition of nitrite. This suppressing effect could not be explained by changes in viable cell yields. This data suggests that the antibody production and cell proliferation of B cells may be influenced by nitrite from activated macrophages in the immune response.     

Electrochemical immunoassay for vitellogenin based on sequential injection using antigen-immobilized magnetic microbeads.

A rapid and sensitive immunoassay for the determination of vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with an amperometric detector and a neodymium magnet. Magnetic beads, onto which an antigen (Vg) was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of magnetic beads in an immunoreaction cell were controlled by means of the neodymium magnet and by adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an alkaline phosphatase (ALP) labeled anti-Vg monoclonal antibody between the fraction of Vg immobilized on the magnetic beads and Vg in the sample solution. The immobilization of Vg on the beads involved coupling an amino group moiety of Vg with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactate film. The Vg-immobilized magnetic beads were introduced and trapped in the immunoreaction cell equipped with the neodymium magnet; a Vg sample solution containing an ALP labeled anti-Vg antibody at a constant concentration and a p-aminophenyl phosphate (PAPP) solution were sequentially introduced into the immunoreaction cell. The product of the enzyme reaction of PAPP with ALP on the antibody, paminophenol, was transported to an amperometric detector, the applied voltage of which was set at +0.2 V vs. an Ag/AgCl reference electrode. A sigmoid calibration curve was obtained when the logarithm of the concentration of Vg was plotted against the peak current of the amperometric detector using various concentrations of standard Vg sample solutions (0-500 ppb). The time required for the analysis is less than 15 min.     

Sequential injection chemiluminescence immunoassay for nonionic surfactants by using magnetic microbeads

A rapid and sensitive immunoassay based on a sequential injection analysis (SIA) using magnetic microbeads for the determination of alkylphenol polyethoxylates (APnEOs) is described. An SIA system was constructed from a syringe pump, a switching valve, a flow-through type immunoreaction cell equipped with a photon counting unit and a neodymium magnet. Magnetic beads, to which an anti-APnEOs monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in and from the immunoreaction cell were controlled by means of a neodymium magnet and adjusting the flow of a carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-APnEOs monoclonal antibody immobilized on the magnetic beads with a sample APnEOs and a horseradish peroxidase (HRP)-labeled APnEOs in the same sample solution, and was based on the subsequent chemiluminscence reaction of HRP on the magnetic microbeads with a luminol solution containing hydrogen peroxide and p-iodophenol. The anti-APnEOs antibody was immobilized on the magnetic microbeads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of the magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced in the immunoreaction cell and trapped in it by the neodymium magnet, which was equipped beneath the immunoreaction cell. An APnEOs sample solution containing the HRP-labeled APnEOs at a constant concentration, and a luminol solution containing hydrogen peroxide and p-iodophenol were sequentially introduced into the immunoreaction cell, according to an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the immunoreaction cell by collecting the emitted light with a lens. A typical sigmoidal calibration curve was obtained, when the logarithm of the concentration of APnEOs was plotted against the chemiluminescence intensity as the number of photons in 100 ms using standard APnEOs sample solutions at various concentrations (0–1000 ppb) under optimum conditions. The lower detection limit defined as IC₈₀ is ca 10 ppb. The time required for analysis is less than 15 min per a sample. The present method was successfully applied to the determination of APnEOs in river water.     

β2-微球蛋白连续表位的免疫亲和质谱研究

采用Endoproteinase Glu-C, Lys-C和Trypsin 3种蛋白酶分别水解β2-微球蛋白, 产生一系列肽段, 利用固定在琼脂糖珠上的单克隆抗体与其发生免疫亲和反应. 利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术, 对抗原决定簇肽段-抗体复合物进行系统研究, 结果表明, 与抗体结合部位即连续表位的位点为肽段(59~69)(DWSFYLLYYTE). 该研究方法简便、准确, 可用来对其它抗原连续表位的快速测定.     

A possible mechanism of fever induced by Nocardia rubra cell wall skeleton (N-CWS) in experimental animals

The characteristics of fever elicited by the cell wall skeleton of Nocardia rubra (N-CWS) and by lipopolysaccharide (LPS) were compared in rabbits, and the possible involvement of the antigenicity of N-CWS was investigated in guinea pigs. In rabbits, fever of more than 0.5 degree C developed after an intravenous (i.v.) injection of 10 micrograms/kg or more of N-CWS, and was monophasic with 30-100 micrograms/kg but biphasic with the highest dose of 300 micrograms/kg. LPS elicited fever with similar characteristics at doses of 0.01-0.1 microgram/kg. With both compounds, the fever was inhibited by indomethacin. Tolerance to N-CWS and LPS appeared after dosing with 30 or 0.1 micrograms/kg, respectively for 10 d. In guinea pigs sensitized with N-CWS, challenge with 1 or 10 micrograms/kg of N-CWS 10 d later, which did not induce fever in the nonsensitized animals, caused fever of more than 0.5 degree C, and delayed-type hypersensitivity (DTH) appeared. N-CWS also elicited fever in nonsensitized guinea pigs bearing N-CWS-sensitized lymphocytes or anti-N-CWS antibody; the fever was higher in the guinea pigs sensitized with the lymphocytes than in those with the anti-N-CWS antibody. In brief, single injections of N-CWS and of LPS elicited fever with similar characteristics, although the potency of N-CWS was weaker. With N-CWS, the fever is proposed to be triggered by the antigenicity of the compound itself, because doses as low as 1 or 10 micrograms/kg elicited fever along with immunological response in N-CWS-sensitized animals, but not in nonsensitized ones.