Immunohistochemistry of sections from a patient with systemic lupus erythematosus. (a) Anti-FDC (follicular dendritic cell) staining within the area known as germinal centre (GC) A. (b) Staining for CD20. FDC staining suggests two possible GCs within close proximity, but B-cell staining shows no clear demarcation. (c) Anti-FDC staining for GC B. (d) staining with anti-CD20. Panels (a) and (b) are consecutive sections, as are (c) and (d). Panels (e) and (f) show B-cell clusters identified using anti-CD20 on serial sections: (e) B-cell cluster C; (f) is B-cell cluster D. The arrows indicate the areas of positive staining for the marker in question. All images: 100×.