Food Allergens
Richard F. Lockey, Dennis K. Ledford in Allergens and Allergen Immunotherapy, 2014
The sensitizing ability of individual foods and severity of clinical reactivity to food allergens correlate with the following classification of food allergens [8]. Class 1 food allergens both sensitize and trigger allergic reactions via the oral route because they are quickly absorbed and distributed to the systemic immune system. However, Class 2 food allergens do not sensitize orally because they are easily digested into small peptides and lose their sensitization potential. They elicit allergy indirectly when ingested by the fact that they cross-react with other allergens, typically inhalant allergens, often described as pollen-food allergy syndrome. Examples include apple, celery, and carrot and their homolog in birch pollen, Bet v 1. Sequential epitopes of allergens consist of amino acids in the primary sequences while conformational epitopes exist as a consequence of three-dimensional folding of the proteins. Allergen-specific IgE-binding sites are routinely limited to short amino acid sequences, either sequential or conformational. Conformational determinants result from proximity of nonsequential amino acids following folding into a three-dimensional structure. Specific cross-reactivity with proteins sharing sufficient sequential and/or conformational homology occurs with similar food allergens as well as other proteins. Therefore, divergent patterns of cross-reactivity and clinically relevant allergic reactions to foods occur in individual patients.
Food allergens
Richard F. Lockey, Dennis K. Ledford in Allergens and Allergen Immunotherapy, 2020
The sensitizing ability of individual foods and severity of clinical reactivity to food allergens correlate with the following classification of food allergens [8]. Class 1 food allergens both sensitize and trigger allergic reactions via the oral route because they are quickly absorbed and distributed to the systemic immune system. However, class 2 food allergens do not sensitize orally because they are easily digested into small peptides and lose their sensitization potential. They elicit allergy indirectly when ingested by the fact that they cross-react with other allergens, typically inhalant allergens, often described as pollen–food allergy syndrome. Examples include apple, celery, and carrot, and their homologue in birch pollen, Bet v 1. Sequential epitopes of allergens consist of amino acids in the primary sequences, while conformational epitopes exist as a consequence of three-dimensional folding of the proteins. Allergen-specific IgE binding sites are routinely limited to short amino acid sequences, either sequential or conformational. Conformational determinants result from proximity of nonsequential amino acids following folding into a three-dimensional structure. Specific cross-reactivity with proteins sharing sufficient sequential and/or conformational homology occurs with similar food allergens as well as other proteins. Therefore, divergent patterns of cross-reactivity and clinically relevant allergic reactions to foods occur in individual patients.
Tumor immunology
Gabriel Virella in Medical Immunology, 2019
Initiation of the process requires the release of tumor antigens into the tumor microenvironment. In general, there are two types of tumor antigens: (1) tumor-associated antigens (TAAs) and (2) tumor-specific antigens (TSAs). TAAs are derived from proteins that are expressed not only by tumors but also by other normal tissues. The difference is that in tumors these proteins are either overexpressed or have undergone some kind of posttranslational modification. For example, a common TAA is derived from the protein mucin-1 (MUC1). MUC1 is a heavily glycosylated transmembrane protein that is expressed on the apical surface of glandular epithelial cells. In tumor cells, MUC1 is overexpressed, underglycosylated, and its expression is no longer limited to the apical surface of cells. These changes in the expression pattern lead to generation of tumor-associated MUC1 antigens that are immunogenic. The immune system can mount a response against these antigens, but there is risk of cross-reactivity with normal tissues. TSAs (also known as neoantigens) are derived from “neoproteins” that are only expressed by the tumor itself. These proteins are different from normal proteins as a result of tumor-specific mutations. Neoantigens derived from these proteins are tumor specific, and immune responses to these types of antigens target only the tumor while sparing normal tissues. Clinical responses mediated by T lymphocytes targeting neoantigens have been identified in different types of cancers.
Blood biomarkers in ischemic stroke: potential role and challenges in clinical practice and research
Published in Critical Reviews in Clinical Laboratory Sciences, 2018
Konstantinos Makris, Alexander Haliassos, Maria Chondrogianni, Georgios Tsivgoulis
Other significant problems include interferences from autoantibodies and other binding proteins that may be present in the biological sample. As with all immunoassays, ELISAs are also prone to cross-reactivity and matrix-effect. Cross-reactivity is the possibility of the antibodies binding to more than one antigen, thereby causing an erroneous result and often a false-positive effect. Another problem is interferences that result from the matrix effects of the samples, which is due to unknown and unspecified factors present in the sample that interfere with the immunoassay. Matrix effect is usually manifested by low recovery of a specific amount of cytokine spiked into a sample or a non-linear dilution of the sample. This can be resolved by preparing the calibrators in a solution that closely resembles the sample, however, the selection of such diluent is not a simple task. In any case, commercial assays should only be used with samples types that these kits are validated for in order to minimize matrix effect. However, this cannot be said with certainty because investigators use homemade assays in their studies. These studies should be used with caution in reviews and meta-analyses.
An update on adverse drug reactions related to β-lactam antibiotics
Published in Expert Opinion on Drug Safety, 2018
Konstantinos Z. Vardakas, Georgios D. Kalimeris, Nikolaos A. Triarides, Matthew E. Falagas
The second step is to fill the knowledge gap regarding the risk of cross-reactions between not only members of the β-lactam superfamily but also specific classes. Newer studies have shown that cross-reactions are not universal and pertain to specific agents with similar side chains or metabolites of the β-lactam core. The risk of a cross-reaction between a cephalosporin and penicillin or another cephalosporin with dissimilar side chains is as low as for any unrelated drug. Therefore, its use is justified in place of another β-lactam or non-β-lactam antibiotic with broader spectrum. An allergic reaction may appear, but this should not be indiscriminately named as cross-reaction as it is well known that patients truly allergic to penicillin are three times more likely to develop new allergies to unrelated substances [132].
Tetracaine from urethral ointment causes false positive amphetamine results by immunoassay
Published in Clinical Toxicology, 2021
Robin Wijngaard, Marina Parra-Robert, Lourdes Marés, Anna Escalante, Emilio Salgado, Bernardino González-de-la-Presa, Jordi To-Figueras, Mercè Brunet
It is known that amphetamine IAs are prone to cross-react with a large number of compounds and therefore commonly associated with FP results [1,4,6,7]. Cross-reactivity typically occurs with structurally similar substances compared to the target compound [1,23]. Amphetamine-like drugs present simple chemical structures, which makes it difficult to develop specific antibodies [2,6,23]. With regards to the mechanism of interference, tetracaine has no obvious two-dimensional structural similarity to the molecules of amphetamine or MDMA, differently to other interfering compounds such as pseudephedrine [15] or bupropion [16], which share the typical phenethylamine structure of the amphetamine-like compounds (Figure 3). However, these extrapolations of potentially interfering compounds due to structural similarity present some limitations in the prediction of true antibody - antigen interactions, as they are more complex and involve a three-dimensional confirmation of the compounds [23]
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