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In a factorial design study a murine anaphylactic shock model was used to analyse the effect of homogenization. pasteurization, and fat content on the ability of bovine milk to induce anaphylactic reactions. Mice were sensitized by either oral or subcutaneous immunizations with various types of bovine milk. In spite of a significantly higher antibody titre in the mice sensitized subcutaneously, there was no difference in the sensitivity between orally and subcutaneously immunized mice with respect to anaphylactic reactions. Pasteurization did not seem to change the ability of milk to induce anaphylactic reactions. However, increasing fat contents in combinations with homogenization resulted in an increase ofthe ability ofthe milk to induce anaphylactic reactions. Tntroduction

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A passive cutaneous anaphylaxis test (PCA) for determination ofthe allergenicity of bovine whey proteins and peptides was developed in mice. Antisera against whey proteins raised in rabbits and in mice, using a procedure for high IgE titre mixed with Freund's incomplete adjuvant, were applied intradermaliy. and various whey proteins and whey protein hydrolysates were tested for positive PCA reaction. Unhydrolysed whey and peptides larger than 6500 Da were found to react positively, peptides between 6500 Da and 3400 Da reacted weakly, whereas peptides smaller than 3400 Da were unable to initiate a reaction. The studies indicate that guinea-pigs, widely used by tradition, may be successfully replaced by mice in determination of the allergenicity of various compounds. The sensitivity ofthe two species is similar, but the husbandry and handling of mice is more convenient, and they are less expensive.

Outbred NMRI mice were sensitized for high IgE production either by subcutaneous injections of low doses of untreated bovine milk or homogenized bovine milk in combination with intraperitoneal injections of Freund's Complete Adjuvant or by oral administration of untreated or homogenized bovine milk without adjuvant. When analysed in murine passive cutaneous anaphylaxis test both types of milk resulted in production of reaginic antibodies against bovine milk proteins when given subcutaneously. When given orally, homogenized milk resulted in reagin production in 10 out of 14 mice, whereas untreated milk resulted in reagin production in only one out of 12 mice. The sensitized mice, and control mice, were orally challenged with either untreated milk, homogenized milk or 0.9% NaCl. Examination of the intestines 40 min after oral administration revealed that homogenized milk, contrary to untreated milk or 0.9% NaCl, resulted in a large increase in the mass of the proximal gut segment of mice sensitized orally with homogenized milk compared with control mice orally challenged with saline (P less than 0.001), and only mice both sensitized and challenged orally with homogenized milk showed degranulation of mast cells in the intestinal wall. By contrast, subcutaneously sensitized mice or mice sensitized orally with untreated bovine milk showed no significant intestinal reaction upon oral challenge with either homogenized or untreated bovine milk. These observations may indicate that the route of sensitization is of great importance when intestinal reactions are to be studied, and that homogenization of bovine milk may render the milk more aggressive with respect to its ability to induce intestinal reactions. The study indicates that mice may be an attractive experimental animal model for mimicking the intestinal anaphylactic reactions of cow milk-allergic humans.