Interleukin-10 (IL-10) is a pleiotropic cytokine involved in several immune responses and expressed by a variety of cell types. IL-10 interacts with at least two subunits of the IL-10 receptors (IL-10R1 and IL-10R2), which are members of the interferon receptor family, and play important roles in ligand binding and signaling. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) methods, the rriRNA expression and secretion patterns of IL-10 were studied. IL-10R1 and IL-10R2 mRNA expression patterns were also Studied in the tumor-derived human B-cell lines. IL-10 protein is expressed and predominantly secreted by AIDS-associated B-cell lines (AABCL). However, IL-10R1 and IL-10R2 are constitutively and ubiquitously expressed in all the B-cell lines included in our study. These results suggest that B-cell IL-10 functions as an autocrine growth factor, in AABCL. Furthermore, we report that higher secretion of IL-10 observed in AABCL could be due to the specific GCC haplotype of IL-10 promoter polymorphisms, although no specific correlation was observed between IL-10 promoter polymorphisms and IL-10 protein secretion as analyzed by PCR-sequence specific primers methodology and ELISA, respectively. (c) 2005 Elsevier Inc. All rights reserved.