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Although recent progress has aided our understanding of the processes that prevent immune tolerance breakdown, this Focus issue illustrates how much remains unknown about susceptibility to and pathogenesis of autoimmune diseases.
The present views of how CD4+ T cells respond to antigen are based largely on artificial systems. A highly sensitive approach that allows normal T cell responses to be monitored in physiological conditions overturns some existing ideas about the differentiation of CD4+ T cells.
Recent advances in microscopy have enabled imaging of cell surface receptors at ever higher resolutions. A report using the latest technology now provides evidence that the T cell antigen receptor and the adaptor Lat are confined to small islands, which cluster together after triggering of the T cell antigen receptor.
The mammalian intestine contains a large number of commensal bacterial strains. New work suggests that antimicrobial peptides used for defense against pathogenic bacteria are also used to adjust the balance among bacterial populations and to control intestinal homeostasis.
