Expression profiling of constitutive mast cells reveals a unique identity within the immune system

Mast cells are evolutionarily ancient sentinel cells. Like basophils, mast cells express the high-affinity IgE receptor and are implicated in host defense and diverse immune-mediated diseases. To better characterize the function of these cells, we assessed the transcriptional profiles of mast cells isolated from peripheral connective tissues and basophils isolated from spleen and blood. We found that mast cells were transcriptionally distinct, clustering independently from all other profiled cells, and that mast cells demonstrated considerably greater heterogeneity across tissues than previously appreciated. We observed minimal homology between mast cells and basophils, which share more overlap with other circulating granulocytes than with mast cells. Derivation of mast cell and basophil transcriptional signatures underscores their differential capacity to detect environmental signals and influence the inflammatory milieu.