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The spleen is a lymphoid organ that filters the blood. It removes old red blood cells and recycles iron. The spleen contains unique populations of immune cells and is thought to be important for protecting the body against certain types of bacterial infection.
Marginal zone B cells provide rapid antibody responses to blood-borne antigens. Cerutti and colleagues identify a RORγt-dependent innate lymphoid cell subset that establishes crosstalk among multiple cell types to enhance antibody responses.
Liver X receptors (LXRs) are transcription factors that respond to sterols. Castrillo and colleagues identify a unique requirement for LXRα in the development of splenic marginal zone macrophages and their antibody responses to blood-borne antigen.
Small, soluble, ubiquitous ligands are difficult to visualize. Schwab and colleagues have created a functional receptor reporter that gauges the in vivo concentration, location and biological action of sphingolipids.