MILK-INDUCED ECZEMA IS ASSOCIATED WITH THE EXPANSION OF T-CELLS EXPRESSING CUTANEOUS LYMPHOCYTE ANTIGEN

The extravasation of T cells at sites of inflammation is critically de pendent on the activity of homing receptors (HR) involved in endotheli al cell recognition and binding. Two such HR (the cutaneous lymphocyte antigen [CLA] and L-selectin) have been shown to be selectively invol ved in T cell migration to skin and peripheral lymph nodes, respective ly. This study was designed to assess the relationship between the org an specificity of an allergic reaction to food and the expression of H R on T cells activated in vitro by the relevant food allergen. Periphe ral blood mononuclear cells were isolated from seven milk allergic chi ldren with a history of eczema when exposed to milk. All patients had a positive prick skin test and double-blind placebo-controlled food ch allenge to milk. 10 children with either allergic eosinophilic gastroe nteritis or milk-induced enterocolitis and 8 nonatopic adults served a s controls. Five-parameter how cytometry using monoclonal antibodies w as used for detection of the specific HR on freshly isolated T cells v ersus T cell blasts induced by a 6-d incubation with casein, as compar ed with Candida albicans. After in vitro stimulation with casein, but not C. albicans, patients with milk allergy and atopic dermatitis had a significantly greater percentage of CLA(+) T cells (P < 0.01) than c ontrols with milk-induced enterocolitis, allergic eosinophilic gastroe nteritis, or nonatopic healthy controls, In contrast, the percentage o f L-selectin-expressing T cells did not differ significantly between t hese groups. These data suggest that after casein stimulation allergic patients with milk-induced skin disease have an expanded population o f CLA(+) T cells, as compared with nonatopics or allergic patients wit hout skin involvement. We postulate that heterogeneity in the regulati on of HR expression on antigen-specific T cells may play a role in det ermining sites of involvement in tissue-directed allergic responses.