Dendritic cells (DCs) express several receptors for the Fc portion of immunoglobulin (Ig)G (FcγR), which mediate internalization of antigen–IgG complexes (immune complexes, ICs) and promote efficient major histocompatibility complex (MHC) class II–restricted antigen presentation. We now show that FcγRs have two additional specific attributes in murine DCs: the induction of DC maturation and the promotion of efficient MHC class I–restricted presentation of peptides from exogenous, IgG-complexed antigens. Both FcγR functions require the FcγR-associated γ chain. FcγR-mediated MHC class I–restricted antigen presentation is extremely sensitive and specific to immature DCs. It requires proteasomal degradation and is dependent on functional peptide transporter associated with antigen processing, TAP1-TAP2. By promoting DC maturation and presentation on both MHC class I and II molecules, ICs should efficiently sensitize DCs for priming of both CD4+ helper and CD8+ cytotoxic T lymphocytes in vivo.

In recent years it has become widely recognized that bacteriophages have several potential applications in the food industry. They have been proposed as alternatives to antibiotics in animal health, as biopreservatives in food and as tools for detecting pathogenic bacteria throughout the food chain. Bacteriophages are viruses that only infect and lyse bacterial cells. Consequently, they display two unique features relevant in and suitable for food safety. Namely, their safe use as they are harmless to mammalian cells and their high host specificity that allows proper starter performance in fermented products and keeps the natural microbiota undisturbed. However, the recent approval of bacteriophages as food additives has opened the discussion about ‘edible viruses’. In this review, we examine the promising uses of phages for the control of foodborne pathogens and the drawbacks on which more research is needed to further exploit these biological entities.

SummaryThe non-pore-forming bacteriocin lactococcin 972 (Lcn972) inhibits the synthesis of peptidoglycan at the septum in Lactococcus lactis. In this work, the genome-wide response of L. lactis MG1614 to Lcn972 was analysed by DNA microarrays. We found 26 genes to be significantly upregulated. Most of these encode membrane proteins of unknown function and the two-component system (TCS) CesSR (formerly known as TCS-D). CesSR orchestrates the response of L. lactis to Lcn972. None of the genes upregulated in L. lactis MG1614 were induced by Lcn972 in L. lactis DcesR. In silico analysis of the promoter regions of the upregulated genes revealed a novel conserved 16 bp palindromic sequence at positions -73/-72 or -46 relative to the putative transcriptional start sites. Point mutations and deletion of this CesR box abolished regulation. Purified His-tagged CesR interacts in electrophoretic mobility shift assays with several promoters carrying the CesR box. The CesR box is also present in other Gram-positive cocci, upstream of genes involved in cell envelope stress. CesSR was strongly induced by lipid II-interacting cationic polypeptides and disruption of cesR increased susceptibility to these antimicrobials. We propose here that CesSR of L. lactis controls the immediate response to cell envelope stress in this organism.