CD1 cell surface glycoproteins represent a family of non-major histocompatibility complex (MHC) encoded antigen-presenting molecules. All members of the CD1 family appear to mediate the recognition of microbial or endogenous lipid and glycolipid antigens. The recognition of CD1d by a unique subset of natural killer (NK) T cells that leads to rapid production of large amounts of both type 1 and type 2 cytokines can be augmented by some synthetic glycolipids. Because of the proposed role of such CD1d-restricted T cells in immunoregulation, we hypothesized that CD1d molecules participate in mucosal immune responses in patients with gastrointestinal symptoms owing to food hypersensitivity. Patients of that category represent a heterogeneous group in which poorly defined immunological mechanisms are believed to contribute to disease pathogenesis. The expression of CD1 in duodenal biopsy samples from six patients with verified intolerance to cow's milk and six healthy controls was studied by immunoperoxidase staining of cryostat sections using a panel of mouse monoclonal antibodies (MoAbs) specific for CD1a, b, c, and d. Large numbers of CD1d positive cells were found in the lamina propria of all the patients, both during the symptomatic and the asymptomatic periods, whereas healthy controls were virtually devoid of CD1d expression in the duodenum. The localization of CD1d positive cells corresponded to areas where B cells, plasma cells and dendritic cells (DC) were present. A positive correlation was found between the numbers of CD1d+ and CD19+ cells in the lamina propria. In contrast to previous reports, no CD1d expression was found on the epithelial cells. Although less numerous than CD1d+, the CD1c+ cells were also present in all the patients and in five out of six controls. No staining for CD1a or CD1b was detected in the duodenal biopsy samples from any of the subjects. The exclusive presence of CD1d in the duodenal lamina propria of the patients with cow's milk hypersensitivity might suggest the participation of these molecules in the pathogenesis of allergic reactions to food.
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