Shared reactivity

There is no publicly available database to share reactive chemical test information. 

Suggested improvements for sharing reactive chemical test data, incident data, and lessons learned. 

Currently, there is no mechanism to effectively share reactive chemical test data throughout industry. The feasibility of a publicly available test database has not yet been studied by industry or government. Reactive chemical experts at one company visited by CSB expressed an interest in working with the National Institute of Standards and Technology (NIST) to develop such a database. 

The specificity of these EIA is determined by the uniqueness of the interaction between antibody and antigen, as well as to environmental factors. Non-specificity of the immune reaction can be traced to two phenomena, shared reactivity and cross-reactivity, discussed in Section 8.6. Specificity of a polyclonal antiserum is generally higher than that of its component antibodies, due to the specificity bonus (Section 8.6). 

In AA procedures, antigens which share reactivity towards the same antibody will be complexed in a ratio proportional to their concentrations (appear equipotent) since the antibodies are present in large excess. Environmental influences have relatively little effect. 

Fig. 8.4. Concepts of shared (I) and cross-reactivity (II). Two antigens (A and B) may have one or more identical epitopes and a subpopulation of antibodies from a polyclonal antiserum will react equally with both antigens (shared reactivity). If monoclonal antibodies against the common epitope were used, it would not be possible to distinguish A and B. In cross-reactivity, antibodies reactive with the homologous antigen are also reactive with different epitopes (generally less fit thus lower affinity).

In contrast to the first, this cross-reactivity is not based on differences in affinity and the term shared reactivity should be used. These two phenomena are schematically represented in Fig. 8.4. 

Fig. 8.5. Effect of antigens with shared (I) or cross-reactivity (II) on the displacement of labeled, bound antigen from the immune complex. Non-labeled specific antigen will displace 50% of the label at a concentration of C,. A cross-reacting antigen generally has a lower affinity and a higher concentration (C2) is required to displace 50% of the labeled antigen. In contrast, antigen with shared reactivity will have the same affinity for a subpopulation of the antibodies and displace the labeled antigen in the immune complex at the same concentrations as the specific non-labeled antigen but only to a certain limit (I) (i.e., only for antibodies for the common...

Methods used in EIH may be extended to other techniques where identification and localization of antigens are important the protein and nucleic acid transfer blots (Chapter 16) may be subjected to these methods. As with EIA, epitopes rather than antigens or molecules are recognized by EIH methods. Shared reactivity and crossreactivity (Section 8.6) may, therefore, interfere as in the AA-type assays (Section 2.3). 

Immunological specificity is best inferred from neutralization or blocking tests. It is fallacious to deduct degrees of cross-reactivity or shared reactivity of a given antiserum in EIH from the results of EIA. Sensitivity and specificity are determined to a high degree by the design of the test as shown in Chapter 2 for the AA and the AM tests, and may, therefore, be very different in EIH and EIA. 

Dermatofibromas and their variants (e.g., nodular histiocytoma, xanthogranuloma, transitional histiocytoma, nodular subepidermal fibroma, aneurysmal cutaneous fibrous histiocytoma, palisading fibrous histiocytoma, epithelioid reticulohistiocytoma) all share reactivity for vimentin, factor Xllla, CDIO, CD68,... 

Martinez-Diaz H, Kleinschmidt-DeMasters BK, Powell SZ, et al. Giant cell glioblastoma and pleomorphic xanthoastrocytoma show different immunohistochemical profiles for neuronal antigens and p53 but share reactivity for class III beta-tubulin. Arch Pathol Lab Med. 2003 127 1187-1191. 

---