Expression of interleukin 10 in B lymphocytes of different origin.

Interleukin 10 (IL-10) is a strong B-cell-activating factor. Since murine Ly1-positive peritoneal or lymphoma B cells strongly express IL-10, we examined malignant cells from patients with acute and chronic leukemias by reverse transcriptase polymerase chain reaction (RT-PCR) for the expression of IL-10 mRNA. High expression was found in three out of four samples from CD10+, CD5- common acute lymphoblastic leukemia (cALL) cells, whereas T-ALL samples generally did not contain IL-10 mRNA. In contrast to the murine system, only low levels of IL-10 expression were seen in 10 out of 11 samples from patients with CD5+ CLL. Myeloid derived cell lines were negative for IL-10. Epstein Barr virus (EBV) positive and negative Burkitt's lymphoma (BL) cell lines showed heterogenous IL-10 expression: BL cell lines with a nonactivated germinal center phenotype (CD10+, CD77+, CD23-, CD30-, CDw70-) expressed little or no IL-10, whereas EBV-positive and negative BL cell lines with an activated phenotype (CD77-, CD23+, CD30+, CDw70+) expressed easily detectable amounts of IL-10 mRNA. The highest expression of IL-10 was found in EBV-immortalized lymphoblastoid cell lines (LCL). Upon superinfection with non-defective EBV, the EBV-negative cell line BL 41 up-regulated IL-10 expression. Thus, in vivo IL-10 expression is not restricted to cells showing a specific (CD5+) phenotype. IL-10 may play an important role in c-ALL. The expression of IL-10 in BL cell lines is correlated to an activated phenotype in vitro and is independent of the EBV carrier status. EBV can induce IL-10 expression.