Fig. 6

Iba1 positive cells in the inner plexiform layer correlate with calretinin discontinuities in the XBP1 fl/fl; Chx10-Cre retina. a Cryosections of 12–14 month retina labeled with the Iba1 antibody (red) and anti-calretinin (green). Iba1-positive cells within the inner plexiform layer (IPL) in WT and XBP1 fl/fl; Chx10-Cre (cKO) show several distinct features. Calretinin labeling within the IPL labels three defined strata (arrowheads). Areas of discontinuity (arrows) are evident. b Iba1-postive cells correlate with areas of calretinin discontinuity twice as frequently (p < 0.03) in XBP1 cKO (n = 5 mice, 66 Iba1+ cells) than in WT (n = 5 mice, 67 Iba1+ cells) retina. (c and d). Additionally, Iba1-positive cells are characterized as having either amoeboid morphology indicating activated microglia (arrow) or ramified morphology indicating resting microglia (arrowhead). There are nearly twice as many (p < 0.01) activated Iba1-positive cells in the IPL of XBP1 cKO retina (n = 7 mice, 103 cells) compared to WT (n = 7 mice, 98 cells). e In contrast, in the outer plexiform layer (OPL), we find no obvious differences in Iba1-positive cell number (WT and cKO, 2 Iba1+ cells per 100 μm) and extensions into outer nuclear layer (ONL; WT, 0.55 and cKO 0.49 extensions per cell) (n = 7 mice, 128 cells) and XBP1 cKO (n = 7 mice, 168 cells). GCL, ganglion cell layer. Scale bar = 25 μm in A, 50 μm in c and e