Antigen antigenic site

Colman, P.M., Varghese, J.N., Laver, W.G. Structure of the catalytic and antigenic sites in influenza virus neuraminidase. Nature 303 41-44, 1983. 

The approximate location of the epitopes for more than 40 monoclonal anti-ATPase antibodies has been mapped to various regions within the cytoplasmic domain of the Ca " -ATPase [285,302-304]. All antibodies were found to bind with high affinity to denatured Ca -ATPase, but the binding to the native enzyme showed significant differences depending on the location of antigenic sites within the ATPase molecule. 

Antibody A52 with its epitope at residues 657-672 [129,139,274,275] inhibited the vanadate-induced crystallization of Ca " -ATPase and decreased the stability of preformed Ca " -ATPase crystals [285]. The vanadate-induced crystals arise by the association of the ATPase monomers into dimers (type A interaction), the dimers into dimer chains (type B interaction), and the dimer chains into 2-dimensional arrays (type C interaction). It is suggested that antibody A52 interferes with type B interactions, preventing the formation of dimer chains, without exerting major effect on the concentration of Ca -ATPase dimers in the membrane. The simplest interpretation of the destabilization of Ca -ATPase crystals by mAb A52 is that binding of the antibody to its antigenic site physically blocks the interaction between ATPase molecules [285]. Considering the large bulk of the antibody, such interference is not unexpected, yet only a few of the antibodies that bind to the Ca -ATPase in native sarcoplasmic reticulum interfered with crystallization. 

Some of the antibodies directed against the B fragment of the Ca -ATPase caused moderate inhibition of ATPase activity and Ca transport the inhibition usually did not exceed 50%, even at high antibody Ca -ATPase ratios where the antigenic sites are expected to be fully saturated [285,302,304],... 

In the rare case when a peptide showing some promise has been identified, further immunization trials are necessary to establish its value as a practical synthetic vaccine. Since peptides are usually poor immunogens and do not mimic well the conformation of the corresponding antigenic site in the... 

Van Regenmortel, M. FI. V. (1998), From absolute to exquisite specificity. Reflections on the fuzzy nature of species, specificity and antigenic sites , J. Immunol. Meth., 216, 37-48. 

Antigens usually are macromolecules that contain distinct antigenic sites or epitopes , which can be recognized and interact with the various components of the immune system. They can exist as individual molecules composed of synthetic organic chemicals, proteins, lipoproteins, glycoproteins, RNA, DNA, polysaccharides—or they may be parts of cellular structures (bacteria or fungi) or viruses (Male et al., 1987 Harlow and Lane, 1988). 

Bendayan, M. (1989) Ultrastructural localization of insulin and C-peptide antigenic sites in rat pancreatic B cell obtained by applying the quantitative high-resolution protein A-gold approach. Am. J. Anat. 185, 205-216. 

Bendayan M, Zollinger M. Ultrastractural localization of antigenic sites on osmium-fixed tissues applying the protein A-gold technique. J Histochem Cytochem 1983 31 101-109. 

Tyramide signal amplification This procedure, designated as a catalyzed reporter deposition (CARD) or tyramide signal amplification (TSA), takes advantage of horseradish peroxidase (HRP) from an HRP-labeled secondary antibody to catalyze in the presence of hydrogen peroxide the oxidation of the phenol moiety of labeled tyramine. On oxidation by HRP, activated tyramine molecules rapidly bind covalently to electron-rich amino acids of proteins immediately surrounding the site of the immunoreaction. This allows an increase in the detection of an antigenic site up to 100-fold compared with the conventional indirect method with no loss in resolution. 

The use of specific antibodies labeled with a fluorescent dye to localize substances in tissues was first devised by A. H. Coons and his associates. At first, the specific antibody itself was labeled and applied to the tissue section to identify the antigenic sites (direct method) (1). Later, the more sensitive and versatile indirect method (2) was introduced. The primary, unlabeled, antibody is applied to the tissue section, and the excess is washed off with buffer. A second, labeled antibody from another species, raised against the IgG of the animal donating the first antibody, is then applied. The primary antigenic site is thus revealed. A major advantage of the indirect method is the enhanced sensitivity. In addition, a labeled secondary antibody can be used to locate any number of primary antibodies raised in the same animal species without the necessity of labeling each primary antibody. 

For the antibody that acts as a receptor of the B-cell, the constant region links the antigenic sites to the membrane... 

Figure 17.22 Antibodies form a complex with bacteria either by linking antigenic sites on several bacteria or by binding to different antigenic sites on a single bacterium.

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