Cell associated C1q complement staining. Paraffin wax sections A1, A2 and A3 (case MS160_S3, active case). A1 shows immunolabelling with anti-C1q in plaque (P) and peri-plaque (PP) areas. A2 shows C1q immunopositive debris (brown) within foamy macrophages localized in the centre of an active plaque. A3 shows C1q immunolabelled on myelin. B1 paraffin wax section double immunolabelled with anti-C1q (grey) and anti-HLA-DR (brown) confirms C1q immunopositive debris located within HLA positive foamy macrophages cells; (case MS160_S3, active plaque). B2 and B3 also show paraffin wax sections with immune double staining of anti-C1q and anti-HLA-DR (case MS230_s2, chronic active plaque). B2 shows HLA-DR positive cells (brown) closely associated with C1q positive myelin (grey) within the white matter. B3 shows co-localisation of C1q on HLA-DR positive microglia (arrows) in the peri-plaque. C1 (case MS372_22, chronic active plaque) and C2 (case MS230_S2, chronic active plaque, stained using immunofluorescence (IFC)) show double labelling for C1q and GFAP, with colocalisation of C1q (grey) and GFAP (brown) in some but not all cells (insert in C1 and arrow in C2 highlighting colocalisation). IFC in figure D1 (case MS377_S2, active plaque) and D2 (case MS160_S1, active plaque) demonstrate anti-HLA-DR positive macrophages closely associated with C1q positive myelin (arrow). Inset in D2 shows C1q immunopositive debris within an HLA-DR immunolabelled macrophage (arrow). E1 shows a myelin sheath at edge of an active plaque staining with anti-MOG (grey) and C1q (brown) (case MS160_S3, arrow); in the same area E2 (IFC, case MS160_S3) shows a myelin sheath with positive anti-C1q immunolabelling. Figures F1 (MS160_S3/1; chronic active plaque) and F2 (MS336_1; active plaque), captured with confocal laser scanning microscopy, show disrupted myelin, immuno-positive for C1q associated with anti-SMI-32 immunopositive non-phosphorylated axon profiles in chronic and active areas. Scale bars are shown for each plate.