Figure 4. Microglial caspase-8 deficiency ameliorates proinflammatory microglia activation in the substantia nigra in response to MPTP. Panel (a) shows an illustration of Iba1 and CD16/32-labeled microglia in the substantia nigra in response to either saline or MPTP in Casp8fl/fl mice and CreLysMCasp8fl/fl mice. Injection of saline in Casp8fl/fl mice was not different from CreLysMCasp8fl/fl mice and hence only Casp8fl/fl mice saline is shown. Inserts are high-magnification photographs to show more precisely the morphological features of microglia. Panels (b) and (c) show the stereological analysis of total microglia (Iba1) (b) or proinflammatory microglia (CD16/32) (c) in the substantia nigra of Casp8fl/fl mice and CreLysMCasp8fl/fl mice after MPTP. Results are the mean ± SD of a minimum of four independent experiments and are expressed as number of cells per mm3. Statistical significance was calculated by analysis of variance followed by the least significant difference post hoc test for multiple range comparisons (p <0.05). Panel (d) shows illustration of dual immunofluorescence of Iba1 and CD16/32-labeled microglia in the substantia nigra in response to saline or MPTP in Casp8fl/fl mice and CreLysMCasp8fl/fl mice. Panel (e) are higher magnification photographs of dot boxes depicted in Note the drastic changes in the microglia morphology in terms of Iba1-labeling in response to MPTP in both Casp8fl/fl mice and CreLysMCasp8fl/fl mice (a, d). Also note how CD16/32-immunolabeled proinflammatory microglia is strongly up-regulated in response to MPTP in Casp8fl/fl mice, particularly in the pars compacta of SN (a,d), this effect being notably hindered in CreLysMCasp8fl/fl mice. Scale bar: a: 350 μm; d: Iba1 and CD16/32 staining: 300 μm; merge: 35 μm.