Expression of Tyk2 and Jak2 protein kinases. Cryosections of retinas from three postnatal ages immunohistochemically stained for Tyk2 (A, B, C) and Jak2 (D, E, F) are shown. The asterisks indicate the positions of the developing inner plexiform layer at P1 (A, D) and the emerging outer plexiform layer at P5 (B, E). The scale bar shown in panel C represents 100 μm for all panels. Arrows in B and E point to positively stained cells located adjacent to the forming outer plexiform layer. The meanings of the abbreviations referred to in this figure are: gcl (ganglion cell layer), inl (inner nuclear layer), ipl (inner plexiform layer), is (inner segment), onl (outer nuclear layer), opl (outer plexiform layer), os (outer segment), rpe (retinal pigmented epithelium), vz (ventricular zone).