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A new mechanism for bacterial uptake in mucosal tissues is proposed that is mediated by dendritic cells endowed with the ability to make intercellular adhesive links directly with epithelial cells thereby preserving the integrity of the gut barrier
The intimate nature of the cellular interactions that occur in the gut epithelium where the mucosal immune system interfaces with the external environment is the subject of this fascinating paper by Rescigno et al. Dendritic cells (DCs ) are arguably the most important cell type in the immune system. Although bewilderingly heterogeneous in phenotype and function, they are the only antigen presenting cell type capable of presenting peptides to virgin T cells, thereby initiating cell mediated immunity to newly encountered antigens. Given the delicate balance which exists in the gut between T cell tolerance and responsiveness to luminal antigens (a breakdown of which is likely to be responsible for food sensitive enteropathies and inflammatory bowel disease), DCs are probably key factors in controlling T cell responses in the gut wall. DCs are present in all organised lymphoid tissues and an earlier report in rats suggested that they might also be present in the gut epithelium.1 This paper presents evidence for a new and exciting mechanism of antigen sampling as it demonstrates for the first time that DCs can penetrate the epithelium to directly take up bacteria from the gut lumen without compromising the barrier function of the gut. This mechanism is facilitated because DCs appear to be endowed with the ability to make homotypic intercellular adhesive links directly with gut epithelial cells. …