Acute Allergic Skin Reactions and Intestinal Contractility Changes in Mice Orally Sensitized against Casein or Whey (1)
Cow’s milk allergy (CMA) is one of the leading causes of food allergy in adults. In developed countries, approximately 2–3% of infants exhibit CMA. Cow’s milk contains 2 main protein classes, caseins (30 g/l) and whey proteins (5 g/l). The caseins consist mainly of aS1-, aS2- and b-casein, whereas whey proteins comprise of b-lactoglobulin, a-lactalbumin, bovine serum albumin, serum immunoglobulins and lactoferrin.
In order to study allergic skin responses, mice were challenged i.d. in the ear pinnae with casein or whey 1 week after the last oral sensitization. One hour after dermal challenge, the allergen-specific acute ear swelling response was maximal when compared to PBS and CT sham-sensitized control mice. Four hours after challenge, the ear swelling turned to basal levels in the casein group, while in the whey-sensitized group the swelling remained slightly enhanced up to 24 h after swelling.
Total IgE concentrations were increased in casein- and whey-sensitized mice in comparison with CT and PBS sham-sensitized mice Casein-specific IgE as well as casein-specific IgG2a levels were not increased. In contrast, casein-specific IgG1 levels were enhanced in the casein-sensitized mice. In the whey-sensitized animals, the whey-specific IgE, IgG1 and IgG2a levels were augmented when compared to the CT sham-sensitized controls. In whey-sensitized mice the acute ear swelling was found to correlate positively with whey-specific IgE whey-specific IgG1. Ear swelling of casein-sensitized mice was not found to correlate with casein-specific IgE, casein-specific IgG1 and casein-specific IgG2a.
The hyporesponsiveness of the colon in the casein-sensitized mice was found to be consistently present in all experiments, while none of these effects were seen in the whey-sensitized animals. The relative amount of water in the feces was increased in the casein- and whey-sensitized animals.
In the casein-sensitized mice, no specific IgE was detected, while the mice indeed showed systemic allergy as seen in the acute allergen-induced ear swelling response. In contrast, the whey-sensitized mice showed the classical characteristics of type I IgE-mediated allergy, scoring positive for allergen-specific IgE and acute ear swelling. Instead of IgE, the acute ear swelling in mice might have been triggered by IgG1 , which is generally known to play a crucial role in mast cell activation in rodents. Mast cell degranulation can occur with immunoglobulin light chain. Immunoglobulin light chain is produced in excess during the formation of immunoglobulins. Hence, casein-specific immunoglobulin light chain may have caused the ear swelling in casein mice with an acute allergic skin response that could not be explained by the presence of IgE nor IgG1. Casein protein is a slowly digested dietary protein, while whey protein is a fast one.
