Characteristics of the Antigen

Idiotypic network. Idiotypic determinants (idiotypes) are unique antigenic epitopes characteristic of the antigen receptors on the surface of T and B cells. They are associated with the variable regions of these receptors. Antibodies produced by B cells as the result of antigenic stimulation can themselves stimulate the production of auto-anti-idiotypic antibodies which have the ability to combine with the B-cell receptor (Ig) and thus can dampen down the immune response. Idiotypes may likewise stimulate the production of T cells specific for idiotypic determinants. Jerne (1974) postulated his... 

Demasking protocol is inappropriate or has been omitted. Some tissue antigens require proteolytic enzyme digestion or heat induced antigen retrieval performed prior to staining. The need for pretreatment depends on the type and extent of fixation, specific characteristics of the antigen and the type of antibody used. Use the pretreatment method recommended by the manufacturer. No single pretreatment is suitable for all applications. 29-33, 51-65... 

Selection of the most appropriate species immunoassay for a given sample type requires knowledge of the characteristics of the antigen targets of the antibodies employed in the tests. The available species immunoassays employ antibodies that can detect a range of protein markers and include tests for raw, cooked, canned, and rendered products. The type of sample must be considered when selecting the appropriate speciation test. 

Section 3.1. outlines several protocols for fixation using as an example the fixative paraformaldehyde, and the recipes for the relevant solutions are given. Numerous other fixatives are available—and others indeed may be preferable— depending on the tissue and the characteristics of the antigen. A list of several alternative fixatives and recipes appears in Section 2.S. and appropriate notes relating to their use are provided although use of these alternative fixatives is not explicitly detailed in the protocols. 

Figure 4.10 Pauling theory of formation of an antibody to an antigen (now known to be incorrect, replaced by the clonal selective theory), (a) The polypeptide chain that will eventually form the antibody encounters the antigen, (b) The peptide chain starts to fold in a manner guided by the three-dimensional characteristics of the antigen, (c) The fully folded antibody is completed. Reproduced with permission from Dr. Olof Ramstrom (1997), The Royal Institute of Technology, Stockholm.

The detection of surface plasmon resonance (SPR) is one of the many techniques that exploit the properties of evanescent waves. This technique uses the intrinsic characteristics of the antigen-antibody complex, like refractive index and the thickness of an immunological layer deposited on a reflecting metal-coated glass surface. SPR involves determining the variation in reflectance (R) as a function of the angle of incidence. 

It was established that Ab to Klebsiella pneumoniae didn t demonstrate the cross-reactivity to antigens of the relative bacterial species so, it could be considered that antibodies investigated was highly specific only to the own antigen. The physical-chemical characteristics of the immunological interaction such as constants of formation of Ag-Ab complex were obtained. The binding constants of immune complex were Ka =(9.7 l.l)-10 and Ka,=(1.7+0.3)T0 (mg/ml)f... 

The polyvalency of IgM causes it to bind more firmly to an antigen than either a univalent or bivalent antibody. In this respect, a single molecule of IgM can cause lysis of a cell. Furthermore, the joining chain (J) has been detected in polymeric IgM and IgA, but not in the other immunoglobulins. About 10% of the IgM in external secretions has the secretory component attached. One wonders whether these characteristics of the IglNI are responsible for its take-over role in the gut, when there is a defective synthesis of IgA as in celiac or in Crohn s disease or in ulcerative colitis. 

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