Deficiency in TLR4 results in increased proliferation of cells reminiscent of RPCs in the early postnatal retina. (A) Semiquantitative PCR of PN6 whole eyes for TLR1–9. (B) Staining for TLR4 of a PN6 eye. (C and D) Pictures of the CE labeled with TLR4 and the endothelial marker CD34 (C) or the epithelial markers cytokeratin 18 (CK18) and AE1/AE3 (D, inset). (E and F) Staining for nestin and TLR4 coexpression (E) or BrdU, Chx10, and TLR4 (F) in the CE. (G) Labeling of BrdU and TLR4 in the CE; right panel is a z axis projection of the boxed area. (H) Pictures of BrdU or Ki67 in the CE and the peripheral retina of WT and TLR4D PN6 mice. (I and J) Quantification of proliferating cells in the CE (I) and in the peripheral retina (J). (K) Quantification of BrdU⁺/nestin⁺, BrdU⁺/Pax6⁺, and BrdU⁺/Chx10⁺ cells. (L–N) Representative pictures of nestin/BrdU (L), Pax6/BrdU (M), and Chx10/BrdU (N) staining. Arrows indicate double-labeled cells. Asterisks denote significant differences between the indicated groups: *, P < 0.05; **, P < 0.01; ***, P < 0.001; Student's t test, n = 4. Error bars represent SEM. Bars: (B) 100 μm; (C–G) 20 μm; (individual cell in G) 10 μm; (H and L–N) 50 μm.