MLKL and infection: Consistent with this, receptor-interacting kinase 3 (RIPK3), the kinase phosphorylating MLKL, was markedly phosphorylated in N2aC24 cells, but not in N2aC24L1-3 cells, after IAV/WSN infection, indicating that RIPK3 is activated in N2aC24 cells, but not in N2aC24L1-3 cells, after IAV/WSN infection (Fig. 2B).