🔍Clue 3: the induction of TLSs correlated with the onset of apoptosis. Furthermore, inhibition of apoptosis prevented the ability of IAVs to induce TLSs. However, induction of apoptosis with drugs, independent of infection, did not induce TLS formation. N/9

🔎Clue 2: induction of TLSs was consistent between IAV strains having either filamentous or spherical virion morphologies. This was in despite of several curious similarities between TLSs and budding IAV filaments. N/8

🔎Clue 1: the induction of TLSs did not occur through the release of paracrine innate immune signals, but did require intracellualr IAV replication. N/7

One mechanism of IAV direct cell to cell spread in vitro is through the formation of long, thin and fragile membrane connections known as Tunnelling Nanotubes (TNTs). Impressively, IAVs trigger the formation of TNTs but it was unknown how they were doing this. N/4