Fig. 4

Microglial activation and complement anaphylatoxin receptor expression in the MS cortex. Expression of the opsonin receptor (CR3/CD11b) and anaphylatoxin receptors C3aR and C5aR identified microglia (arrows in a–c) in the MS grey matter, some of which closely apposed neurons (identified by Smi32 immunoreactivity or haematoxylin counterstain) in the demyelinated cortex (a–c). C5aR expression identified activated microglia (d) and the density of HLA-D+ and C5aR+ microglia was elevated in MS cortical lesions in comparison to normal-appearing grey matter (e, f). Example of an activated microglial cell associated with a C3b+ neuron (g). The number of HLA-D+ and C5aR+ cells were significantly correlated and the number of C5aR+ cells associated with activation of the classical and alternative complement pathways (h). e, f, Bar graphs of group means ± standard deviations; Mann-Whitney test. h, Spearman non-parametric comparison of the density of immunopositive cells in the demyelinated MS cortex. Scale bars: a, b, 20 μm; c, d, g, 10 μm