ACKR2 and infection: In humans, ACKR2 is expressed by lymphatic endothelial cells, trophoblasts and some leukocyte populations.4, 5, 6, 7, 8 In mice, we have recently found that, among leukocytes, ACKR2 is highly restricted to innate-like B cells (IBCs) (that is, marginal zone and B1 B cells), and is the best unifying marker of these cells.9 IBCs serve key roles during homeostasis, autoimmunity and infection, and new properties of these cells continue to be defined.