IL-21 promotes autophagy expression in neuronal cells after hypoxia/ischemia. (a) Il21r mRNA expression relative to GAPDH expression levels is shown in normoxic and hypoxic primary mouse neurons after OGD or control treatment. (b) Viability of Neuro2A cells treated with the indicated doses of IL-21 after OGD. (c) Il21r mRNA expression relative to GAPDH in neuronal (Neura2A), astrocytic, and endothelial cell lines (MB114) expressed relative to BMDC expression. (d) ATG6 expression in primary neurons treated with PBS, etoposide, or 32–256 ng/ml rIL-21 for 4 h after 1–2 h oxygen glucose deprivation as measured by RT-PCR. Cells treated in triplicate. (e) Number of ATG6⁺ cells per field in the same regions of WT and IL-21 KO mouse brains after tMCAO as assessed by immune staining (n = 3 mice per group). Arrows indicate ATG-6⁺ cells in periinfarcted brain tissue of WT and IL-21 KO mice. Bars, 100 µm. Data are representative of two independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001 by Student’s t test (single comparison) or one-way ANOVA (multiple comparisons). Error bars indicate SEM.