Interaction of E. coli with dendritic cells--a model for studies of graft infections

The rejection process of skin allografts is mediated by dendritic cells (DC) and lymphocytes. The recipient DCs are engaged not only into an allogenic but also antibacterial reaction to the penetrating bacteria. The capacity of these cells to sample sites of pathogen entry, respond to microbial signals and activate naive T cells suggests a critical role for DC in initiating antimicrobial immunity. In our study, we investigated the ability of the green fluorescent protein (Gfp) labelled E. coli to infect DC. We studied kinetics of in vitro and in vivo adherence and incorporation of E. coli by rat spleen and bone marrow (BM) DC. Bacterial adherence to the cell surface was observed after 2 h incubation of DC with bacteria. A 24-hour culture of DC from both sources was followed by bacterial adherence to all cells and engulfment by at least 50% of cells. There was an increased expression of the phenotypic markers on the DC cultured with E.coli. The Gfp-labelled E.coli should be useful for studies of the activation of dendritic cells. The method will allow to study the process of simultaneous activation of DC by allo- and bacterial antigens.