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Scanning electron micrograph of the distal small intestine of a mouse. Remnants of the mucus layer (green) overlie the villi (blue fingerlike projections). In this month's Perspective, Gordon and colleagues (p 569) propose that the mucus layer coating the intestinal epithelium is where microbial consortia are assembled. This polysaccharide-rich biofilm may enable intestinal symbionts to gain a foothold in this distinctive niche to benefit both themselves and their host. Photo from Gordon and colleagues; cover by Lewis Long.
Conventional wisdom holds that autoreactive thymocytes always undergo negative selection. This paradigm should be reassessed in light of evidence showing that alternative T cell lineages can develop in certain autoreactive conditions.
Dendritic cells induce and control immunity in the lymphoid organs. Signals derived from the innate and acquired immune systems seem to control dendritic cell lifespan and function by distinct molecular mechanisms.
The assembly of antigen receptor genes in developing lymphocytes through V(D)J recombination is regulated through a mostly undefined but broadly relevant process referred to as 'accessibility'. New findings raise the possibility that wide-ranging, antisense transcription through unrearranged antigen receptor loci could be involved in modulating recombinational accessibility.
Human caspase-12, unlike that found in the mouse, is not involved in apoptosis and thus its physiological function is unclear. However, a unique polymorphism of human caspase-12 has demonstrated its importance in innate immunity.
Dendritic cells sense and respond to multiple signals that are then conveyed to lymphocytes to direct appropriate immune responses. This flow of information is bidirectional, as antigen-experienced T cells also influence dendritic cell function.