Malignant T cells produce IL-10 and STAT-3 is phosphorylated within the tumor microenvironment. (A) PBMCs obtained from CTCL patients were cultured in the presence of PMA, ionomycin, and brefeldin A. Malignant T cells were identified as before and intracellular staining for IL-10 was performed. A representative example is shown (n = 2). (B) Plasma was obtained from normal donors (n = 24) and T-cell NHL patients (n = 25) and IL-10 levels were determined (mean ± 95% confidence interval is shown; P = .04). (C) Immunohistochemical analysis of pSTAT3 expression in CTCL biopsy specimens was performed (n = 10). Three representative examples are shown (×200).