Location of SDF-1–, MIP-3α–, and BCA-1–producing cells in the tonsil.

Frozen human tonsil sections were stained with the biotinylated anti–SDF-1 mAb (red) and anti–cytokeratin-19 (A,B) or anti-CD10 (C) mAbs (all shown in blue). SDF-1–expressing cells are found in the crypt (A,B) but not in the germinal center (GC), the follicular mantle (FM), or the T zone (T) in (C). The photomicrograph in panel B shows a higher-magnification view of the crypt seen in panel A. The section in panel D was stained with anti–MIP-3α (red) and anti–cytokeratin-19 (blue) Abs, while the section in panel E was double-stained with anti–SDF-1 (red) and anti–MIP-3α (blue) Abs. (F,G,H) Tonsil sections were double-stained with anti–BCA-1 (red) and anti-CD2 (F), anticytokeratin-19 (G) or anti-CD35 (H) (all in blue) Abs. BCA-1 is expressed by clusters of cells in the crypt and in the B-cell follicles (F). High-magnification views of the crypt show that BCA-1–expressing cells in this site do not express cytokeratin-19 (G) or CD35 (H). Magnifications are × 5 for panels A, C, D, and F; × 20 for panel G; × 40 for panel H; and × 100 for panels B and E. The stainings are representative of 5 different tonsil specimens. The arrow head indicates double positive cells; *, lumen of the crypt.