Definitions epitope

Polyclonal antibodies can react with many epitopes, whereas MAbs are restricted to one epitope on proteins that do not have repeating sequences.24 By definition, polyclonal immunoassays are generally much more sensitive but less specific than monoclonal assays. Bispecific or hybrid antibodies can be used to increase the affinity. Bispecific antibodies are formed by the fusion of two previously established hybridomas to produce antibodies displaying the binding characteristics of both of the antibodies in one molecule.25... 

Precise definition of the host-protection epitope(s) of the Taenia and Echinococcus vaccine antigens would be valuable if it were to lead to the development of a synthetic vaccine or provide reagents to assist with quality control of vaccine production. Identification of a limited number of host-protective fragments may allow the recombinant antigen to be replaced by synthetic peptides. This would have significant advantages in the production... 

In light of the above-mentioned difference of opinion, and in the absence of a definite understanding regarding unmasking of an epitope or whole antigen molecule as a result of unmasking treatments (heat or nonheat treatment), both terms, epitopes and antigens, are used in this volume. 

In contrast to enzyme activities, the definition of the proteo-hormone measurands as well as of many tumor markers and cardiac markers is very critical and several aspects have to be regarded as it concerns the epitope to be detected, the sub-unit to be measured (/3-chain or complete molecule) and finally the glycosidic structure of the molecule. 

As many B cell epitopes are described to be conformational (Aalberse, 2000), peptides identified by sequential approaches may render limited information and might exhibit reduced antibody-binding affinity. In a very stringent definition, conformational epitopes are composed of amino acids from different loci in the allergen sequence brought into proximity by the tertiary structure of the protein. Systematic characterization of conformational epitopes is much more difficult compared to linear epitopes, because it requires knowledge of the 3D structure, which is often limited. 

In the example, the achievement of objectives 1/2 (70% purity) and 1/3 (immunoreactive in vitro) could be used as milestones which successfully conclude the antigen preparation phase. However, the definition "immunoreactivity in vitro" seems too inexact for use as a milestone. A better and adequate specification could be for example "immunoreactive with monoclonal antibody Y", whereby antibody Y is directed against the most relevant epitope of Antigen X. 

No definitive study of the effects of protein carrier on response is available, and many carrier proteins have been used, including globulins, albumin, hemocyanin, thyroglobulin, and fibrinogen. The optimal number of haptens, or the epitope density, is also controversial, but a density of 8 to 25 haptens per bovine serum albumin molecule is probably optimal (12),... 

This new definition of immunocytochemistry derives from advances in antibodylabeling methods in recent years. These advances resulted from specific needs in animal research. Initially, formalin-fixed paraffin sections were used for immuno-histochemistry however, results were inconsistent. In most cases, the antibody did not label anything or it labeled too many cells and was dubbed over fixed. This problem led to the development of the epitope retrieval or antigen retrieval methods, where sections of tissue are treated with heat in buffers before antibody incubations. Unfortunately, epitope retrieval methods can be unique from antibody to antibody and also, for the same antibody, from tissue to tissue. Epitope retrieval is complicated and best avoided. For animal research, a simple method was then developed where tissue was fixed in paraformaldehyde and not formalin or alcohol and subsequently frozen sections were cut on a cryostat. This eliminated the steps of dehydration, embedding in paraffin, rehydration after sectioning, and epitope retrieval before antibody incubation. This was a major breakthrough. 

A word of caution on screening using indirect ELISA is necessary. mAbs do show exquisite specificity, by definition. Solid-phase coating of antigens can affect certain epitopes in that they change their conformation. This prevents some mAbs from reacting (being dependent on conformation). Thus, in some cases, mAbs will be missed in the indirect ELISA. 

Figure 23 shows the features of mAbs relevant to the ELISA. Although the mAb is, by definition, a specific reagent with respect to the binding to epitopes, the physical state of the mAb, its density, and the distribution of epitopes all affect assay performance. 

Cholesteryl 6-O-palmitoyl- p-u-galactopyranoside 49 was recently identified as a major surface component.The synthesis of the spacer-arm glycolipid-analogue 49 was accomplished as well as the BSA conjugate, allowing the definition of the epitope recognized by human antibodies. 

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