A Major Step towards Defining the Elusive Stumpy Inducing Factor in Trypanosoma brucei

Trypanosoma brucei stumpy forms are the only stage that can transmit from human to tsetse fly. Stumpy formation is regulated by a quorum sensing mechanism that depends on parasite density and an unknown stumpy induction factor (SIF). Recently, an elegant study by Matthews and colleagues (Cell 176, 1–12) has identified several crucial components of this pathway, including the putative SIF and its receptor