Antigens cross-reactivity

A negative result in this type of test indicates that the potential to sensitise is extremely low and that human exposure is unlikely to be attended by a significant incidence of sensitisation. Because the test can be overpredictive, some toxicologists recommend that a non-adjuvant test such as the Buehler test should be used if a positive is obtained, to give a more realistic determination of the prevalence of human sensitisation, it should be remembered that contact sensitisation is a persistent condition thus once sensitised to a chemical, an individual is at risk of dermatitis whenever exposed to the same or antigenically cross-reactive chemical, for example, nickel in jewellery. 

Studies on the white clover -Rhizobium trifolii interaction are the most advanced. Trifoliin A, a lectin present in clover-seedling roots, binds hapten reversibly to carbohydrate antigens cross-reactive on the capsular polysaccharide of R. trifolii and clover epidermal-cells.244 A specific hapten that inhibits binding of trifoliin A to both surfaces is 2-deoxy-D-arabino-hexose.245 It has also been shown that levels of trifoliin A on root hairs decline with increasing concentrations of nitrate, in parallel to root-nodule development,246 and that lectin receptors are transient on R. trifolii, in a way coinciding with its capacity to be adsorbed to clover roots.247... 

The SDI is reliable as a measure of antigenic cross-reactivity only if it represents the average value calculated from a large number of bleedings... 

Fig. 1. Quantitative measurement of antigenic cross-reactivity between several tobamo-viruses assessed by indirect ELISA on antigen-coated plates. A, Homologous reactions , A, , and O, heterologous reactions with increasingly distantly related viruses. The SDI value separating the homologous reaction (A) from the most distant heterologous reaction (O) was 14.5 — 8.8 5.7. [From M. Jaegle and M. H. V. Van Regenmortel, J. Virol. Methods 11,189 (1985).]...

Influenza viruses belong to the orthomyxoviridae family. There are three types of influenza virus, named A, B and C (from the chronological order of their characterization). A multitude of subtypes have been characterized for type A virus. These have arisen from the antigenic cross-reactivities of the surface glycoproteins (see below). No subtypes have been identified for types B and C. Influenza type C virus is significantly different to the other two and in this work only influenza viruses A and B are discussed. Influenza virus particles are spherical in shape, approximately 100 nm in diameter. A schematic diagram of the virus is shown in Fig. 1. 

Normal chicken cells, carrying the chicken-helper factor, express a surface glycoprotein which is antigenically cross-reactive with determinants of the major envelope glycoprotein of avian myeloblastosis virus. ... 

A homologous protein has been isolated from the urine of dogs used in kidney transplantation experiments (297). The sequence of the N-ter-minal 42 residues was determined and found to be identical to that of the human protein at 35 or 36 positions. Nevertheless, antigenic cross-reactivity was not observed. Rabbit antibodies were used antibodies from a nonmammalian species are generally more discriminatory in this type of comparison. Since 2X0. was also detected in chimpanzee serum (297), it may be anticipated that the homolog of /82m will be found in many mammalian species. 

One reliable method for identifying a class as homologous to that of a human immunoglobulin is antigenic cross-reactivity. Amino acid sequence homologies, which are more deflnitive, are also available in some instances. 

The sodium-dependent inorganic phosphate transporter SLC34A1 (NaPi-lIa) is not localized in the mouse brain a case of tissue-specific antigenic cross-reactivity. J Histochem Cytochem 59 807-812... 

Hoffman, D.R., 1993, Allergens in Hymenoptera venom XXV The amino acid sequences of antigen 5 molecules and the structural basis of antigenic cross-reactivity. J. Allergy Clin. Immunol 92 707-716. 

Lu, G., Villalba, M., Coscia, M.R., Hoffman, D.R., and King, T.R, 1993, Sequence analysis and antigenic cross-reactivity of a venom allergen, antigen 5, from hornets, wasps and yellow jackets. J. Immunol. 150 2823-2830. 

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