Cross-reactivity

Cross-reactivity is the reaction between an antibody and an antigen that differs from the immunogen. It is sometimes also referred to as crossimmunity or cross-protective immunity.^[1] A few examples of cross-reactivity have been confirmed in humans, one of which involves influenza virus-specific CD8+ T cell and hepatitis C virus antigens.^[2]

An adaptive immune response is specific to the antigen that stimulated it (called the immunogen). However, many naturally occurring 'antigens' are a mixture of macromolecules (e.g. from pathogens, toxins, proteins, pollen) comprising several epitopes. Contact with a complex antigen such as a virus will stimulate multiple immune responses to the virus' different macromolecules as well as the individual epitopes of each macromolecule. For example, the tetanus toxin is a single protein macromolecular antigen but will stimulate many immune responses due to the tertiary structure of the protein yielding many different epitopes.

Medicinal uses for this idea include immunization to bacterial infections. The toxin that creates the immune response will have an epitope on it that stimulates the response. Denaturing the protein may 'disarm' its function but allow the immune system to have an immune response thus creating an immunity without harming the patient.

Cross-reactivity is also a commonly evaluated parameter for the validation of immune and protein binding based assays such as ELISA and RIA. In this case it is normally quantified by comparing the assays response to a range of similar analytes and expressed as a percentage. In practice, calibration curves are produced using fixed concentration ranges for a selection of related compounds and the mid-points (IC50) of the calibration curves are calculated and compared. The figure then provides an estimate of the response of the assay to possible interfering compounds relative to the target analyte.

Examples

Hevein-like protein domains are a possible cause for allergen cross-reactivity between latex and banana.^[3]

References

1. ^ Porrozzi, R; Teva, A; Amaral, VF; Santos Da Costa, MV; Grimaldi Jr, G (2004). "Cross-immunity experiments between different species or strains of Leishmania in rhesus macaques (Macaca mulatta)". The American journal of tropical medicine and hygiene 71 (3): 297–305. PMID 15381810. 
2. ^ Kasprowicz, Victoria; Ward, Scott M.; Turner, Alison; Grammatikos, Alexandros; Nolan, Brian E.; Lewis-Ximenez, Lia; Sharp, Charles; Woodfruff, Jenny et al. (2008). "Defining the directionality and quality of influenza virus–specific CD8+ T cell cross-reactivity in individuals infected with hepatitis C virus". Journal of Clinical Investigation 118 (3): 1143–53. doi:10.1172/JCI33082. PMC 2214846. PMID 18246203. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2214846. 
3. ^ Hevein-like protein domains as a possible cause for allergen cross-reactivity between latex and banana. Mikkola JH, Alenius H, Kalkkinen N, Turjanmaa K, Palosuo T and Reunala T.J, Allergy Clin Immunol. 1998 Dec, 102(6 Pt 1), pages 1005-1012, PubMed

External links

• MeSH Cross+reactions
• http://pathmicro.med.sc.edu/mayer/ab-ag-rx.htm