Mouse Ear Swelling Test MEST

The MEST uses both topical and injection exposures for induction and a topical challenge of the pinnea in which visual evaluation is replaced by measuring ear thickness with an engineer s micrometer. Its purpose is to evaluate the response of mice following the challenge with potential sensitizers. 

If the control groups show more than a 10% increase, the study should be repeated using lower doses. The percentage of respondents is calculated. The degree of ear swelling should also be calculated by dividing the thickness of the ear to which the test material was applied by the thickness of the vehicle 

Gad and co-workers (1986,1887) presented validation studies of 72 compounds and reported a false-negative rate of only 2 % and no false-positives when comparing MEST to GPMT data on the same materials. The incidence of sensitization in MEST was consistently lower than that produced by GPMT. Similar findings were reported for comparisons between the Buehler assay and MEST in the same paper. More recent publications have confirmed that the incidence of positive response in MEST is consistently lower than that in GMPT, and weak and moderate sensitizers are not identified correctly (Comacoff et al. 1988 and Dunn et al. 1990). 

Although numerous approaches to developing a predictive sensitization assay in mice have been proposed, MEST is one of only two assays sufficiently developed to warrant consideration as standardized assays (LLNA being the other). The MEST has been accepted by the Environmental Protection Agency for registration of chemicals under the Toxic Substances Control Act (TSCA). 

The type of micrometer used may affect interpretation of the test results. When Van Loveren et al. (1984) compared the use of spring-loaded caliper-type instruments with screw and friction thimble micrometers, the spring-loaded instruments were found to be the best. This should be taken into account for future modifications of the MEST. In addition, the use of anesthetic can be eliminated by operator training and prior handling of animals. 

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Gad, S. C. et al., Development and validation of an alternative dermal sensitization test the mouse ear swelling test (MEST), Toxicol. Appl. Pharmacol., 84, 93, 1986. 

Cell-mediated immunity Cytotoxic T lymphocyte killing delayed type hypersensitivity response mouse ear swelling test (MEST Gad et al., 1986) guinea pig maximization test (Magnusson and Kligman, 1969). 

Gad S.C., Dunn, B.J., Dobbs, D.W. and Walsh, R.D. (1986) Developmental and validation of an alternative dermal sensitization test The Mouse Ear Swelling Test (MEST), Topical Appl. Pharmacol. 84 93-114. 

Cornacoff JB, House RV, Dean JH (1988) Comparison of a radioisotopic incorporation method and the mouse ear swelling test MEST) for contact sensitivity to weak sensitizers. Fund Appl Toxicol 10 40-44 Dunn BJ, Rusch GM, Siglin JC, Blaszcak DL (1990) Variability of a mouse ear swelling test (MEST) in prediction of weak and moderate contact sensitizers. Fundam Appl Toxicol 5 242-248... 

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