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Results for “Binding Sites, Antibody”

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At least 19 recordsLinked to original sources
PubMed1976

Tryptic cleavage of antibody binding sites from hepatitis B surface antigen particles.

The sedimentation of radiolabelled 22 nm hepatitis B surface antigen particles was unaffected by treatment with either trypsin or SDS alone, but combined treatment disrupted the particulate nature of the radiolabelled material. Considerable antibody binding activity by the group-specific determinant (a) was preserved after combined SDS and trypsin treatment but was released from the bulk of the radiolabelled protein; gel filtration indicated an approximate mol. wt. of 5000 to 15000 for the released antibody binding material. This material was precipitated by concanavalin A, suggesting the presence of carbohydrate. Its serological activity was remarkably resistant to boiling and to proteolytic digestion, but was partially sensitive to treatment with 0-01 M-periodate or with mixed carbohydrases and neuraminidase, and was greatly reduced by treatment with reducing agent. These data suggest that the stability of the a determinant is due to the structure of the antibody binding site itself, rather than to involvement in the quaternary structure of the particle, and that intact disulphide bonds and carbohydrate, closely related to the antibody binding site, are necessary for the full expression of serological acitivity.

Binding Sites, Antibody↗
PubMed1977

Structural and dynamical aspects of membrane immunochemistry using model membranes.

Three different phospholipid haptens have been synthesized, in which the haptenic group is the paramagnetic nitroxide (spin-label) group. These lipid haptens differ from one another in the length and composition of the molecular chain linking the 2,2,6,6-tetramethylpiperidinyl-N-oxy moiety to the phosphodiester group of the lipid. These lipid haptens have been incorporated at low molar concentrations (0.01 to 0.5 mol %) in liposomes containing various proportions of cholesterol and dipalmitoylphosphatidylcholine (DPPC). A study has been made of specific antinitroxide IgG (and Fab) binding to these liposomes, and the fixation of complement. From these studies we conclude: (a) For lipid haptens whose possible extension above the bilayer plane is limited (e.g., approximately 10-20 A), antibody binding and complement fixation depend strongly on the hapten structure and host lipid composition, because of steric limitations on the accessibility of lipid haptens to the binding sites in the protein. (b) Complement fixation by specific IgG antibodies directed against the nitroxide group as part of a lipid hapten depends strongly on the lateral mobility of the lipid hapten when its molar concentration in the plane of the membrane is of the order of 0.1 mol % or less. It is likely that this conclusion applies to many lipid haptens, and possibly other membrane components. (c) The inclusion of cholesterol in lipid membranes has at least two distinct effects on complement fixation involving lipid haptens. Through a steric effect on bilayer structure (probably involving lateral molecular ordering) cholesterol in phosphatidylcholine bilayers can enhance hapten exposure to antibody binding sites, enhance antibody binding, and thereby enhance complement fixation. It is likely that cholesterol also affects complement fixation at low hapten concentrations through a modification of membrane fluidity.

Animals↗
PubMed1975

Specific isolation and characterization of antibody directed to binding site antigenic determinants.

The preparation and specificity of antibodies specific for the ligand-binding site of HOPC 8, a phosphorylcholine (PC)-binding mouse myeloma protein, are described. Antiserum to HOPC 8, prepared in rabbits, was adsorbed with an HOPC 8-Sepharose immunoadsorbent and anti-binding site antibodies were eluted with PC. These antibodies reacted with HOPC 8 but not other myeloma proteins, including those with PC-binding specificity different from HOPC 8; the specificity of this anti-HOPC 8 antibody for the combining site region of HOPC 8 was shown by the fact that 1) the interaction of the anti-HOPC 8 antibody preparation with HOPC 8 was completely blocked by PC and 2) the antibody preparation failed to bind TEPC 15 in which the combining sites had been blocked by covalently bound PC groups. Moreover, these anti-binding site antibodies did not react with isolated heavy or light chains, indicating the requirement for a heavy-light chain interaction. By contrast an idiotypic antiserum to HOPC 8 prepared in A/J mice did bind affinity-labeled TEPC 15 and the reaction with HOPC 8 was only marginally hapten inhibitable. Both of the idiotypic determinants detected by these two antisera were present on anti-PC antibody raised in BALB/c mice;

Adsorption↗
PubMed1977

Interaction of thyroid-stimulating antibodies with the human thyrotrophin receptor.

Thyroid-stimulating antibodies (TSAb) were found to inhibit the binding of labelled thyrotrophin (TSH) to thyroid membranes in a dose-dependent manner and this effect was localized in the Fab part of the TSAb molecule. Analysis of the binding data suggested that TSAb and TSH bound to the same receptor site. Production of cyclic AMP by the thyroid membranes was stimulated by TSAb and TSAb-Fab with a similar time course to that observed with TSH. Kinetic studies indicated that the binding of TSAb to the thyroid membranes was not rate-limiting in the process of stimulation of cyclic AMP production.

Antibodies↗
PubMed1975

Relation of thyroid-stimulating immunoglobulins to thyroid function and effects of surgery, radioiodine, and antithyroid drugs.

Thyroid-stimulating immunoglobulins (T.S.I.) have been detected in the serum of all patients with untreated Graves' disease, and in these patients the levels of T.S.I. correlated significantly with the early uptake of 131I by the thyroid. The frequency of T.S.I. in patients treated solely by antithyroid drugs, by radioiodine, or by partial thyroidectomy was 53 per cent, 50 per cent, and 17 per cent, respectively. The reduced frequency of T.S.I. in the serum of patients treated by drugs or radioiodine was probably due to spontaneous remission, but in the case of partial thyroidectomy the operation itself clearly had a dramatic effect on the serum-T.S;I. These results accorded well with the reported frequency of thyroid autonomy in similar groups of patients and suggested that thyroid-stimulating immunoglobulins were responsible for hyperthyroidism in Graves' disease.

Adenylyl Cyclases↗
PubMed1977

Investigation of immunological relationships among myosin light chains and troponin C.

Two classes of myosin light chains can be distinguished functionally: those that restore calcium regulation to "desensitized" scallop myofibrils, and those that do not (Kendrick-Jones, J., et al. (1976), J. Mol. Biol. 104, 747--775). Despite this functional classification, chemical analyses reveal few patterns unique to regulatory light chains, and, indeed, sequence comparisons suggest structural similarities between both classes of myosin subunits (Collins, J. H. (1977), Nature (London) 259, 699--700; Kendrick-Jones, J., and Jakes, R. (1977), in International Symposium on Myocardial Failure at Tegernsee, Riecker, G., and Boehringer, Ed., Munich, West Germany, Springer-Verlag, pp. 28--40). Immunological assays using antisera to regulatory and to nonregulatory light chains showed no correlation between antigenic activity and the presence or absence of regulatory function. Weak cross-reactivity was observed, however, among myosin light chains and troponin C, consistent with the suggestion made on the basis of sequence homologies that these subunits contain similar structural domains (Weeds, A. G., and McLachlan, A. D. (1974), Nature (London) 252, 646--649). Unexpectedly, the strongest cross-reactivity observed was that between the vertebrate myosin alkali 1 and DTNB light chains.

Animals↗
PubMed1976

Pulmonary angiotensin-converting enzyme antienzyme antibody.

A method has been developed for quantitating anticatalytic activity in antibody preparations made in goats against pure solubilized angiotensin-converting enzyme from rabbit pulmonary membranes. Anticatalytic activity was purified about 90-fold from a single batch of serum by a procedure including diethylaminoethylcellulose chromatography and elution from Sepharose columns containing covalently bound pure enzyme. Antiholoenzyme antibody was fractionated with respect to charge and binding affinity; however, these different populations each inhibited enzymatic hydrolysis of hippurylhistidylleucine, angiotensin I, and bradykinin. The inhibition dose-response curves were similar for hydrolysis of hippurylhistidylleucine and angiotensin I despite the difference in molecular weight of these substrates. Evidence is presented suggesting that a single molecule of antibody can bind two molecules of enzyme and that at least 18% of the total antiholoenzyme antibody population is directed against determinants which influence catalytic activity. A competitive immunoassay was developed with radioiodinated pulmonary enzyme as displaceable antigen. The anticatalytic and radioimmune assays were used to examine immunological properties of converting enzymes in various rabbit organs and fluids. Kidney, brain, and serum were found to contain converting enzymes which were immunologically identified with that in rabbit lung. Converting enzyme in seminal plasma was similar to the lung enzyme in the anticatalytic assay, but showed lower immunoreactivity in the radioimmune assay.

Animals↗
PubMed1977

Antibodies specific to a deoxyribodinucleotide sequence.

Antibodies were raised in rabbits against the bovine serum albumin conjugate of dpApT. Analysis by double diffusion in agar gel and quantitative precipitation test showed the presence of antibodies specific to the hapten in the antisera. Quantitative data on the specificity of the antibodies were obtained by studying the inhibition of the binding of 3H-dpApT to the antisera by various nonradioactive mono- and oligonucleotides, using a nitrocellulose membrane binding assay. The antibodies were found to be highly specific for the dinucleotide sequence dpApT. The antibodies were able to bind to synthetic oligonucleotides containing the sequence dpApT and to denatured calf thymus DNA.

Animals↗
PubMed1979

Effect of quantity and quality of IgG antibodies on blocking of allergenic histamine release in vitro.

In a study of the protective role of IgG antibodies in allergen injection therapy, serum antibodies to timothy grass allergens were raised in rabbits and tested for inhibition of histamine release from basophils of grass pollen-sensitive human subjects. Rabbit sera were not inhibitory until late in the immune response when large amounts of relatively low affinity IgG antibodies were detected by primary binding. Inhibition of histamine release by late sera required preincubation of allergen and antibody prior to addition of sensitive basophils, and could not be demonstrated when basophils and IgG antibodies had simultaneous access to allergen. Hence intravascular inhibition of mediator release in allergen-treated patients may require high affinity IgG antibodies. The predominantly low affinity of antibodies raised in the rabbits precluded testing of this possibility.

Allergens↗
PubMedDate not supplied

Polyfunctional antibodies. Their biology and inheritance.

It seems likely that immunoglobulins have evolved from some archetypal molecule and those forms which are useful to the animal have been retained. It is this entire population of antibodies which forms the humoral immune system and in such a system, not only the properties of individual antibody combining regions, but the properties of the multiprotein system as a whole, are important for the defences of the body against pathogens. Antibody combining sites may bind a disparate set of structurally related and unrelated ligands. This multispecificity can be biologically meaningful: the same clone can be stimulated by different antigens. In this sense, cell surface immunoglobulins are multifunctional. The major biological consequence of antibody multispecificity is overlapping binding functions within subsets of the total antibody repertoire. The most significant impact of this overlap is: (1) it reduces the number of V genes necessary to code for the total number of combining sites; (2) the cross-stimulation of clones by structurally related and unrelated antigens may be instrumental in the normal maintenance of immune responsiveness and in addition, it may explain the ability to respond to unusual and less ubiquitous antigens; (3) the antigenic history of the animal may contribute to the maturation of the immune response by cross-stimulation of pre-selected clones of antigen binding cells.

Animals↗
PubMed1977

A new method of applying the Sips equation.

The Sips equation is frequently used in immunochemistry to describe the relationship between antibody-binding site concentration (n0[Ab]), antigen concentration, intrinsic affinity constant (K), and the heterogeneity index (a) of the affinity constant. Usually n0[Ab] is determined before calculating the remaining parameters (K and a). A new method is proposed which does not require knowledge of n0[Ab] nor an extensive calculation to determine K and a. The method can also be used to determine the antibody-binding site concentration without purified antibody or ligand saturation of the binding sites. This method can be applied to any antibody which binds a monovalent ligand and which can be obtained at a concentration greater than 1/K. Since the Sips equation can be applied to any ordinary chemical reaction by setting a=1, the proposed method can be used generally to determine the affinity constant and the initial concentration of one of the reactants.

Animals↗
PubMed1979

Conformation-specific antibodies to the alpha chain COOH terminus of hemoglobin A0.

An anti-hemoglobin antiserum obtained from a sheep immunized with human carboxyhemoglobin A0 demonstrated little difference in its reactivity with deoxy- or carboxyhemoglobin A0. However, a subpopulation of this antiserum isolated by synthetic peptide affinity chromatography clearly distinguished between these two hemoglobin species. This subpopulation, designated alpha(129-141) anti-hemoglobin antibodies, represents less than 1% of the total anti-hemoglobin antibodies. They are nonprecipitating by Ouchterlony analysis, and fluorescence-quenching studies demonstrate the interaction of a single antibody binding site per hemoglobin dimer. These antibodies bind preferentially to carboxyhemoglobin with a median affinity constant of 5 X 10(8) M-1 compared to binding to deoxyhemoglobin with a binding affinity of less than 1 X 10(8) M-1. Furthermore, the presence of these antibodies in stoichiometric amounts increases the oxygen affinity of hemoglobin, and thus antibody and oxygen binding to hemoglobin can be considered as a linked function.

Antibodies↗
PubMed1978

Nerve growth factor in mouse and rat serum: correlation between bioassay and radioimmunoassay determinations.

High levels of nerve growth factor (NGF) determined by competition radioimmunoassay do not agree with values obtained by bioassay. This discrepancy is illustrated here with rat and mouse serum as examples in which values up to 1000 ng/ml have been found by using competition radioimmunoassays. An explanation for the discordant results is presented: serum components bind NGF with an intermediate affinity (Kd = 10(-7) M) but with a very large capacity (up to 0.5 mg of NGF per ml of rat serum). The binding of 125I-labeled NGF to serum components competes with the binding to the solid-phase antibodies (Kd = 10(-9)M) present in limiting amounts, according to the principle of competition radioimmunoassays. Thus, less radioactivity is recovered bound to the antibodies and this gives the erroneous impression that NGF is present. To overcome this difficulty, a two-site radioimmunoassay has been developed which utilizes nonlimiting numbers of antibody binding sites. This assay provides a reliable determination of NGF levels in serum and it can be shown that in rat and mouse serum (either sex) there is less than 5 ng of NGF per ml, in agreement with the results of the bioassay.

Animals↗