The use of T bag synthesis with paper discs as the solid phase in epitope mapping studies

Epitope mapping with synthetic peptides bound to derivatized paper discs has been investigated using the discs both as a solid-phase matrix for peptide synthesis as well as the solid phase in immunologic testing procedures without detachment of the peptides from the paper discs. Using the T bag (tea bag) method the simultaneous synthesis and subsequent immunologic testing of large numbers of peptides was demonstrated for the feline major allergen Fel d I. A total of 15,000 paper disc-bound peptides, comprising the 146 nonapeptides overlapping by eight amino acid residues on both chains, were synthesized simultaneously with 100 paper discs per T bag. Using these paper disc-bound peptides as the solid phase in radioimmunoassays the binding sites found coincided with those detected in the PEPSCAN with the commercially available epitope mapping kit and with the binding sites that had been found with Sepharose-coupled peptides. The signal to background-ratio in the paper disc-RIA was comparable to that in the PEPSCAN and the reproducibility was good. The bound antibodies could be eluted from the paper disc-bound peptides, permitting regeneration and repeated use of the paper discs for immunologic testing. This method was shown to be a useful alternative to the PEPSCAN and to have the major advantage that large numbers of antibodies could be tested with large numbers of peptides simultaneously.

Epitope mapping of the cat (Felis domesticus) major allergen Fel d I by overlapping synthetic peptides and monoclonal antibodies against native and denatured Fel d I

The major cat allergen Fel d I is a homodimer of which each monomer consists of two disulfide-linked polypeptide chains: chain 1 (70 amino acid residues) and chain 2 (92 amino acid residues). Twenty-one synthetic peptides of 14 amino acid residues length, overlapping by seven residues and spanning the entire sequence of both chains, were synthesized. These peptides were coupled to CNBr-activated Sepharose-4B and used as solid-phase antigens in epitope-mapping studies with monoclonal antibodies against native and reduced/alkylated Fel d I. Two monoclonal antibodies directed against reduced/alkylated chain 1 bound to the overlapping peptides 53-66 and 60-70 of chain 1. The monoclonal antibody directed against reduced/alkylated chain 2 bound to the overlapping peptides 36-49 and 43-56 of chain 2. Binding specificity was demonstrated by inhibition by reduced/alkylated Fel d I for all three monoclonal antibodies. Another monoclonal antibody against reduced/alkylated Fel d I had been found to bind predominantly to reduced/alkylated chain 2 on immunoblot in previous studies. It bound to peptides 1-16 and 60-70 of chain 1 and peptides 1-14 and 50-63 of chain 2; it is therefore probably directed against a conformational epitope formed by these four regions. Possibly because of low affinity of this monoclonal antibody, specificity of its binding could not be verified by inhibition studies. A panel of monoclonal antibodies directed against native Fel d I bound to peptides 1-16 and 60-70 of chain 1 and peptides 1-14 and 43-56 of chain 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of pH in determining the cell-type-specific residual activity of glucocerebrosidase in type 1 Gaucher disease

The properties of control and 370Asn-->Ser glucocerebrosidase, the frequently encountered mutated form of the enzyme in type 1 Gaucher disease, were studied in vitro as well as in situ. The catalytic properties of purified 370Asn-->Ser glucocerebrosidase were highly dependent on the assay conditions. The enzyme was deficient in activity towards substrate and in reactivity with the irreversible inhibitor conduritol B-epoxide (CBE) when activated by the bile salt taurocholate. In the presence of more physiological activators, the lysosomal activator protein saposin C and phosphatidylserine, the 370Asn-->Ser enzyme was near normal in kinetic properties at pH values approximately 5, but not at higher pH. In intact fibroblasts, the enzymic activity of the 370Asn-->Ser glucocerebrosidase and its reactivity with CBE were found to be clearly deficient. However, in intact lymphoblasts from the same patients, the behavior of the mutant enzyme was near normal. The catalytic efficiency of 370Asn-->Ser glucocerebrosidase in situ was also found to be highly pH dependent. When intact lymphoblasts were cultured in the presence of permeant weak bases, which increase the pH of acidic intracellular compartments, the catalytic efficiency of the mutant enzyme, as assessed by its reactivity with CBE, became markedly impaired. Our findings indicate that the intralysosomal pH in the intact cell can be expected to have a critical influence on the activation state of 370Asn-->Ser glucocerebrosidase and its ability to hydrolyse substrate. This phenomenon may partly underly the marked heterogeneity in clinical manifestation of Gaucher disease among patients with this mutated form of glucocerebrosidase.

Heterogeneity in the IgE binding to a peptide derived from the house dust mite allergen Der p II indicates that the IgE response is highly polyclonal

The fine specificity of IgE antibody binding to peptide 65-78 of the house dust mite major allergen Der p II was examined by comparison with binding to two peptides in which the cysteines corresponding to cys73 and cys78 in Der p II were substituted by serines and methionines. Differences in binding behavior indicated that at least three different subpopulations of IgE antibodies bound to peptide 65-78. Even at the level of such a small fragment the IgE response in individual donors proved to be polyclonal.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2,2',4,4',5,5'-hexachlorobiphenyl on vitamin K-dependent blood coagulation in female germfree WAG/Rij-rats

Newborn infants are susceptible to bleeding disorders caused by a vitamin K deficiency, so called 'haemorrhagic disease of the newborn' (HDN). These bleedings often occur in infants after medication of the mother with antiepileptics, such as phenobarbital or phenytoin. It has been suggested that an increase in the late type of HDN in exclusively breast-fed infants might be related to the presence of cytochrome P450-inducing polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in human milk. In order to study this possible mechanistic relationship 5-week-old, germfree, female WAG/Rij-rats were exposed to a single oral dose of either 1 microgram 2,3,7,8-tetrachlorodibenzo-p-dioxin/kg body weight (TCDD) or 30 mg 2,2',4,4',5,5'-hexachlorobiphenyl/kg body weight (HxCB), representing cytochrome P-450 1A (3-methylcholanthrene type) and 2B (phenobarbital type) inducers. During the experiment blood coagulation time from each rat was measured. Also, hepatic 7-ethoxy-(EROD) and 7-pentoxyresorufin O-dealkylating (PROD) activities and total cytochrome P450 content were measured. Blood coagulation time (Thrombotest) in the HxCB-treated rats was significantly prolonged and positively correlated to PROD activity and total P450 content. No clear effect of TCDD on coagulation time could be observed under these experimental conditions. These results suggest involvement of P450 2B isoenzymes in vitamin K metabolism.

Autophagic degradation of peroxisomes in isolated rat hepatocytes

Degradation of the peroxisomal enzymes fatty acyl-CoA oxidase and catalase was studied in hepatocytes isolated from rats treated with clofibrate and from control rats. Hepatocytes were incubated in the absence of amino acids in order to ensure maximal flux through the autophagic pathway and in the presence of cycloheximide to inhibit protein synthesis. (1) Degradation of the two peroxisomal enzymes in hepatocytes from clofibrate-fed rats, but not in hepatocytes from control rats, was much faster than that of other intracellular enzymes. This increased degradation of the peroxisomal enzymes was almost completely prevented by 3-methyladenine, an inhibitor of macroautophagic sequestration. (2) The increased degradation of the peroxisomal enzymes was also inhibited by a long-chain (C16:0) and a very-long-chain (C26:0) fatty acid, but not by C12:0, a medium-chain fatty acid, or by C8:0, a short-chain fatty acid. These results provide direct evidence for the proposal that autophagic sequestration can be highly selective [(1987) Exp. Mol. Pathol. 46, 114-122]. It is concluded that preferential autophagy of peroxisomes is prevented when these organelles are supplied with their fatty acid substrates.

Turnover of peroxisomal vesicles by autophagic proteolysis in cultured fibroblasts from Zellweger patients

Previous studies have shown that in fibroblasts from patients with the Zellweger syndrome (ZS) aberrant membrane structures are present which contain peroxisomal membrane proteins (Santos, M. J. et al., Science 239, 1536-1538 (1988)). In order to characterize these structures we have performed double labeling immunoelectron microscopy experiments using antisera directed against the 69 kDa peroxisomal integral membrane protein (PMP) and lysosomal hydrolases. The results indicate that at least 80% of the structures earlier referred to as 'peroxisomal ghosts' contain lysosomal hydrolases. In addition, we have studied the effect of culture of ZS fibroblasts in the presence of 3-methyladenine, an inhibitor of autophagy, on the intracellular distribution of the 69 kDa PMP. Immunofluorescence experiments showed that in the presence of 3-methyladenine there is an increase in fluorescent spots and a change in the distribution of the spots from mainly perinuclear to randomly distributed throughout the cytoplasm. Double labeling immunoelectron microscopy revealed that after culture in the presence of 3-methyladenine the 69 kDa PMP also accumulates mainly in compartments containing lysosomal hydrolases. In one ZS cell line we found that after culture in the presence of 3-methyladenine there was also an accumulation of structures which were as small as normal microperoxisomes. We conclude that in ZS fibroblasts the 69 kDa PMP is mainly present in lysosomal compartments, presumably degradative autophagic vacuoles. Furthermore, in ZS fibroblasts peroxisomes of apparently normal morphology may be synthesized, but they are degraded by autophagic proteolysis.

Epitope mapping of the Dermatophagoides pteronyssinus house dust mite major allergen Der p II using overlapping synthetic peptides

Fourteen synthetic peptides of 15 amino acid residues length, overlapping by five residues and spanning the entire sequence of the major allergen Der p II from the house dust mite Dermatophagoides pteronyssinus were synthesized. These peptides were coupled to CNBr-activated Sepharose-4B and used as solid-phase antigens in epitope mapping studies using human IgE antisera. These antibodies bound predominantly to the peptide comprising residues 65-78, the binding of which was inhibited by native Der p II. In addition these antisera bound, to a lesser extent, to the peptide that comprised residues 1-15, which binding was not inhibited by native Der p II. Thus, we found one sequential epitope for a number of IgE sera.

Prediction of RNA secondary structure, including pseudoknotting, by computer simulation

A computer program is presented which determines the secondary structure of linear RNA molecules by simulating a hypothetical process of folding. This process implies the concept of 'nucleation centres', regions in RNA which locally trigger the folding. During the simulation, the RNA is allowed to fold into pseudoknotted structures, unlike all other programs predicting RNA secondary structure. The simulation uses published, experimentally determined free energy values for nearest neighbour base pair stackings and loop regions, except for new extrapolated values for loops larger than seven nucleotides. The free energy value for a loop arising from pseudoknot formation is set to a single, estimated value of 4.2 kcal/mole. Especially in the case of long RNA sequences, our program appears superior to other secondary structure predicting programs described so far, as tests on tRNAs, the LSU intron of Tetrahymena thermophila and a number of plant viral RNAs show. In addition, pseudoknotted structures are often predicted successfully. The program is written in mainframe APL and is adapted to run on IBM compatible PCs, Atari ST and Macintosh personal computers. On an 8 MHz 8088 standard PC without coprocessor, using STSC APL, it folds a sequence of 700 nucleotides in one and a half hour.

Selective retention of toxic polychlorinated dibenzo-p-dioxins and dibenzofurans in the liver of the rat after intravenous administration of a mixture

A mixture of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), purified from fly ash from a municipal incinerator, was administered as a single intravenous dose to male rats. Livers were analyzed after 5 h, 1, 2, 4, 7 and 9 days for PCDD and PCDF content. Starting from t = 5 h 2,3,7,8-substituted congeners were the predominant PCDDs and PCDFs retained. 2,3,4,6,7-PnCDF was the only congener without 4 lateral chlorine atoms retained in the liver. For most of the 2,3,7,8-substituted congeners reliable half-lives could not be calculated due to the short experimental period. For only three 2,3,7,8-substituted congeners was a complete elimination from the liver found, within this time period. These congeners were 2,3,7,8-TCDF, 1,2,3,7,8- and 2,3,4,6,7-PnCDF with half-lives of less than 1, 2.1 and 1.6 days, respectively. The other PCDDs and PCDFs, without 4 lateral chlorine atoms, were not detected in the liver from 5 h to 9 days after i.v. administration. Based on the congeneric distribution patterns, it is suggested that besides metabolism, structural specific binding to the Ah-receptor and cytochrome P-450 complex might also be responsible for this selective liver retention.

An improved procedure for the isolation of lamellar bodies from human lung. Lamellar bodies free of lysosomes contain a spectrum of lysosomal-type hydrolases

We have recently shown that lamellar body fractions purified from human lung contain a distinct acid alpha-glucosidase distinguishable from lysosomal acid alpha-glucosidase in that it does not cross-react with antibodies raised against the lysosomal enzyme and does not bind to concanavalin A (De Vries, A.C.J., Schram, A.W., Tager, J.M., Batenburg, J.J. and Van Golde, L.M.G. (1985) Biochim. Biophys. Acta 837, 230-238). In order to study the relationship between the non-concanavalin A-binding alpha-glucosidase and lamellar bodies more closely a method was developed for the further purification of the organelles. A purified lamellar body preparation isolated from human lung homogenate by discontinuous sucrose density centrifugation was subjected to gel filtration with Sepharose 4B followed by Percoll density gradient centrifugation, which yielded a lamellar body preparation with a phospholipid phosphorus/protein ratio of 12.57 +/- 0.38 (mumol/mg) (n = 3) as compared to a ratio of 3.34 +/- 0.16 (mumol/mg) (n = 3) in the sucrose density gradient preparation. Concomitantly there was a 3.3 +/- 0.1 (n = 3)-fold enrichment in the content of total acid alpha-glucosidase and a 3.2 +/- 0.1 (n = 3) -fold enrichment of non-concanavalin A-binding acid alpha-glucosidase. The new purification method removes adhering proteins without changing the phospholipid composition. During the successive purification steps the concanavalin A-sensitive and -insensitive alpha-glucosidases remained fully lamellar body fraction associated. Differences between a lysosome-enriched fraction and a lamellar body preparation at varying stages of purification with respect to the ratio between soluble acid hydrolases and the membrane-associated lysosomal enzyme glucocerebrosidase indicate that the purified lamellar bodies were not contaminated with lysosomes. The absence of lysosomes in the purified lamellar body fraction was confirmed by experiments with the weak base glycyl-L-phenylalanine-beta-naphthylamide, which is an artificial substrate for the lysosomal enzyme cathepsin C and brings about lysis of lysosomes. Morphological examination by electron microscopy endorses the absence of contaminating vesicles and organelles and showed a structural integrity of the lamellar bodies in the final preparation. The improved isolation procedure strongly suggests that the concanavalin A-insensitive acid alpha-glucosidase is endogenous to lamellar bodies and supports our earlier idea that it can be used as a lamellar body-specific marker enzyme. In addition, the experiments show that lamellar bodies free of lysosomes contain a spectrum of lysosomal-type enzymes.

Characterization of dendritic cells, isolated from normal and stimulated lymph nodes of the rat

Non-lymphoid dendritic cells were isolated from normal and paratyphoid vaccine-stimulated lymph nodes draining the rat skin. They were studied using enzymecytochemical, immunocytochemical and electron-microscopical methods. These cells had an irregular outline and an eccentrically situated nucleus. All showed acid phosphatase activity in a central area and expressed Ia antigen on the plasma membrane. Birbeck granules were exclusively present in dendritic cells isolated from lymph nodes in the induction phase of the immune response. This observation concurs with the presence of Birbeck granules in interdigitating cells in situ during the same period of the immune response. It is concluded that the dendritic cells are the in-vitro equivalents of the non-actively phagocytizing population of interdigitating cells.

Lymph node accessory cells in the immune response. The primary response to paratyphoid vaccine in rat parathymic lymph nodes

The immune response in the rat parathymic lymph node was studied after administration of antigen into the peritoneal cavity. Special attention was paid to the accessory cells, which might induce the response. During the induction phase of the response a heterogeneous population of non-lymphoid mononuclear cells was present in the subcapsular sinus and the cortex of the node. These cells resemble "veiled cells" described in skin draining lymph and interdigitating cells in the paracortex of skin draining lymph nodes, but they do not contain Birbeck granules. It is concluded that the appearance of these granules depends on the site of the exudate provocation and that the presence of the organelles in these accessory cells is not obligatory for lymphocyte stimulation.

The heterogeneity of follicular center cell lymphomas. I. Cytohistologic, immunologic, and enzymehistochemical aspects

Histologic material from 44 patients with follicular center cell lymphomas with a follicular growth pattern was divided into five groups on the basis of the predominating neoplastic cell type(s), i.e., small centrocytes with occasional centroblasts (SCC), centrocytes and few (CBCC/A) or many (CBCC/B) centroblasts, small and large centrocytes (SLCC), and small and large centroblasts (SLCB). Histologic, immunologic, and enzymehistochemical parameters as observed in these groups were compared, and follow-up material and material obtained during staging procedures were studied. Immunologic and enzymehistochemical findings confirmed both the B-cell origin and the neoplastic nature of the lymphomas, but did not yield relevant differences between the various groups. The groups with a predominance of small centrocytes or of small centrocytes and centroblasts showed the most prominent follicular growth and early dissemination to bone marrow and spleen. Histologic transformation in these groups was characterized by an increase in the number of centroblasts and a more diffuse growth pattern. The groups composed of small and large centrocytes or centroblasts tended to a more diffuse growth and had later dissemination and no histological transformation.

Adjuvanticity of dimethyl dioctadecyl ammonium bromide in guinea pigs. I. Skin test reactions

The effect of the adjuvant dimethyl dioctadecyl ammonium bromide (DDA) on the induction of cellular immunity in guinea pigs was studied. DDA, a surface-active lipid, was mixed with the antigen bovine serum albumin (BSA) or with a conjugate of BSA and dinitrophenol (DNP22--BSA) and injected into the footpads of guinea pigs. At varying intervals skin tests were performed to test the immediate and delayed hypersensitivity (DH) reactions. Optimal DH reactions to BSA were observed from 3 to 6 weeks after immunization with BSA in DDA. The hapten-specific response to DNP22--BSA had an optimum at 3 weeks and was highly specific for the homologous antigen. Histological examinations of skin test sites confirmed that the reaction was rather of the tuberculin type than of the cutaneous basophil hypersensitivity type. When guinea pigs were immunized with DNP22--BSA in Freund's complete adjuvant (FCA) a long-lasting DH to both carrier and hapten groups developed but the DH was always complicated by an Arthus reaction due to antibodies to the DNP hapten. In conclusion, DDA is superior to FCA as adjuvant for the induction of a state of pure DH in guinea pigs.