CD2 and keratoconus: To further assess the role of CD58/CD2-mediated costimulation in KC-dependent T cell activation and STAT1 signaling in an independent experiment, we analyzed the phosphorylation, which reflects activation of STAT1 and other STAT molecules linked to Th1 and Th17 differentiation in T cells cocultured with untreated or IFNγ-pretreated KCs for 24 h.