Subject cross-reactivity

The analytical response generated by an immunoassay is caused by the interaction of the analyte with the antibody. Although immunoassays have greater specificity than many other analytical procedures, they are also subject to significant interference problems. Interference is defined as any alteration in the assay signal different from the signal produced by the assay under standard conditions. Specific (cross-reactivity) and nonspecific (matrix) interferences may be major sources of immunoassay error and should be controlled to the greatest extent possible. Because of their different impacts on analyses, different approaches to minimize matrix effects and antibody cross-reactivity will be discussed separately. 

Biological techniques, e.g., immunoassays, are among the most sensitive analytical methods, but are limited by the availability of the specific antisera and are subject to cross-reactivity. Huang et al. [36] employed an enzyme-linked immunosorbent assay (ELISA) for determination of estradiol, its conjugates, and ethynylestradiol in wastewaster treatment plant effluents (see Table 4). The reported limit of detection (LOD) of 0.1 ng L 1 reflects the sen-... 

Teuber, S.S. and W. R. Peterson. Systemic allergic reaction to coconut (Cocos nucifera) in 2 subjects with hypersensitivity to tree nut and demonstration of cross-reactivity to legu-min-like seed storage proteins new coconut and walnut food allergens. J Allergy Clin Immunol 1999 103(6) 1180-1185. 

In 1972, skin applications of 0.01Z and 0.1Z CS were used to determine the effects of skin pigment on susceptibility to sensitization, sensitizing and Irritating concentrations of CS, and cross-sensltlzatlon with CN. Eighty-six tests were summarized, and results are available on 45 cases. Seven of 15 subjects were sensitized In skln-plgment experiments subjects with lighter skin seemed more susceptible to sensitization. Twenty previously CS-sensltlve subjects showed no cross-reactivity to CN, although 18 developed primary Irritation dermatitis when exposed to 0.2Z CN. Four of 20 subjects developed primary Irritation dermatitis when exposed to 0.1Z CS, but not to 0.01X CS. 

Unlike clenbuterol, salbutamol is a difficult compound to analyze due to its particular chemical attributes. It is a basic compound subjected to protein binding poor recoveries are obtained especially when protein precipitation techniques are used to prepare the extracts (145). In addition, salbutamol is charged at all pH values and does not readily lend itself to simple, specific back-extracting procedures. This severely restricts the options of sample cleanup. However, a Subtilisin protease digestion step followed by acid clarification and solid-phase extraction has been suggested (146) as an adequate extraction and cleanup procedure prior to the end-point determination of salbutamol by an enzyme immunoassay (139) based on the cross-reactivity of anticlenbuterol antibodies. 

Significant immunogenicity and protection against systemic or nasal challenge with live strains of GAS in mice was observed (Sabharwal et al. 2006) when subjected to subcutaneous and intranasal immunization with GAS CHO conjugated to tetanus toxoid. In parallel, analyses of serum samples and throat cultures from Mexican children revealed an inverse relationship between high serum titers of anti-GAS CHO antibodies and the presence of GAS in the throat. Moreover, no cross-reactivity of anti-GAS CHO antibodies with human tissues or cytoskeletal proteins was observed. 

In contrast to human antibodies derived from large naive or synthetic human antibody libraries, antibodies from immune animals were subjected to in vivo selection and are therefore more likely to recognize a given antigen selectively (i.e., without cross-reactivity to another antigen). 

Beta-endorphin is a frequently measured opioid peptide. Immunoassay is the method of choice for the analysis of plasma (3-endorphin. Both RIAs and direct IRMAs have been developed for this purpose. Commercial reagent kits are widely available, and many commercial reference laboratories offer P-endorphin assays. The concentrations of P-endorphin are usually very low to undetectable in normal subjects, and it may be necessary to use extraction procedures to detect meaningful concentrations in plasma. The specificity of commercial antibodies for p-endorphin relative to p-LPH varies widely in some immunoassays, 50% cross-reactivity is seen with p-LPH. With polyclonal antibodies, results may be spuriously high owing to crossreactivity with serum immunoglobulin G (e.g., in patients with immunoglobulin G myeloma). 

Caution should also be exercised when assaying samples from subjects who are receiving oral contraceptives or estrogen replacement therapy because cross-reacting steroids may cause elevated results. Most notably, cross-reactivity with estrone is as high as 10% for some assays, but much lower (<1%) in others. This is likely due to a difference in the specificity of the antibody used for estradiol. Similar effects have been observed for metabolites conjugated at the 3 position, like estrone-3-sulfate and estrone-3-glucuronide. ... 

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