IL-10 expression in CNS lymphomas. Absent IL-10 expression in normal brain (A) with strong expression of IL-10 by lymphoma cells in PCNSL (B), as demonstrated by immunohistochemistry. There was weak or absent IL-10 expression by tumor vessels (×1000). (C) Quantitative RT-PCR demonstrates markedly increased expression of IL-10 in diagnostic specimens of PCNSL (N = 23) compared with reactive tonsils and specimens of normal brain. The average IL-10 transcriptional expression was also higher in PCNSL compared with 9 cases of nodal DLBCL, of which 7 were of germinal center B-cell phenotype. Notably, the normalized IL-10 transcript level, 12, in the 1 nodal activated B-cell-type DLBCL specimen was similar to the mean-normalized IL-10 expression in the PCNSL cases. (D) Mean CSF IL-10 protein is >70-fold higher in patients with both PCNSL and SCNSL compared with neuro-inflammatory conditions and other brain tumors (P < 2.3 × 10−5). The CSF concentration of IL-10 was highest in relapsed cases.
