In this week’s episode we first review new work revealing the critical role of the tension-sensitive cation channel PIEZO1 in the transendothelial migration of leukocytes. We’ll also review new research suggesting that CD8+ T-cells dimly expressing the CD4 antigen are increased in patients with various forms of secondary HLH, a finding that may have diagnostic, prognostic, and therapeutic significance. Finally, we’ll review a large, genome-wide association study identifying the ABO O blood group as a novel risk factor for heparin-induced thrombocytopenia—a finding that could have implications for prediction of this syndrome and for the management of related conditions.