Specimens were shock frozen in liquid nitrogen and stored at –20°C. Cryostat sections (5 µm) were postfixed with acetone for 10 minutes. Thereafter, sections were rinsed in 0.05M phosphate-buffered saline solution (pH 7.4). Endogenous peroxidases were blocked by incubation in 0.3% hydrogen peroxide for 30 minutes. Nonspecific binding was minimized by incubation with fetal calf serum (1:20) for 20 minutes. The avidin-biotin-peroxidase complex method was used for detection of immunostaining, as described elsewhere.21 Briefly, the following antibodies were used: monoclonal (mc) anti-CD3 (1:200), mc anti-CD4 (1:100), mc anti-CD8 (1:200), mc anti-CD22 (1:100), mc anti-CD23 (1:3000), mc anti-CD38 (1:2000), mc anti-CD68 (clone KP1, 1:10 000, all mouse) (Dako, Glostrup, Denmark), and polyclonal anti–IL-16 (1:100, goat) (R&D, Wiesbaden, Germany). Slides were incubated with the primary antibody for 1 hour. After washing, slides were incubated with a biotinylated secondary antibody for 30 minutes (1:200) (Vector Lab, Burlingame, Calif). An avidin-biotin-peroxidase complex (Vector Lab) was added for 30 minutes after washing. Finally, peroxidase reaction was performed using 0.01% 3-amino-9-ethylcarbazole (Sigma, Munich, Germany) as chromogen. Omission of the primary antibody abolished the immunohistological staining completely. Haemalum staining was performed as the last step of the procedure to counterstain the nuclei.