Interleukin-10 (IL-10) seems to play an important role in modulating intestinal inflammation and may be involved in the development of oral tolerance as well. IL-10-deficient mice show evidence of intestinal inflammation that is histologically and clinically similar to inflammatory bowel disease. IL-10 inhibits interferon-γ(IFN-γ)-mediated effects such as activation of macrophages. The IL-10 receptor (IL-10R) is most related to the IFN-γ receptors. The post-receptor-binding effects of IFN-γ have been shown to be mediated by the JAK-STAT pathway, but the signaling pathways for IL-10 have not been elucidated. We hypothesize that IL-10 follows signal transduction pathways that overlap IFN-γ, resulting in antagonism or competition between factors along the IFN-γ pathway. Utilizing the same kinase pathway, we hypothesize that IL-10 may target transcription directed by the IFN-γ response element and/or thesis-inducible element (SIE). We generated a 933 base pair cDNA encoding for the carboxy terminus, the cytoplasmic domain, of the IL-10R. Using the pMAL bacterial expression system, we were able to express this truncated IL-10R fusion product with maltose binding protein (MBP). This MBP-IL-10R protein was then loaded onto an MBP-affinity column. Then, cell lysates of IL-10-induced and non-induced U937 cells (a human monocyte cell line) were passed over the column and the MBP-IL-10R-protein complex was eluted off. An SDS/PAGE gel was run of the protein extracts and Western blotting performed with anti-JAK-1 antibody. Western analysis revealed that the IL-10-treated cells express a protein that is bound by the JAK-1 antibody that is not seen in the untreated cells. This assay suggests that IL-10 induction of monocytes results in active expression of the JAK-1 kinase, as is seen with IFN-γ receptor binding. Further studies are ongoing to determine if this effect occurs in intestinal epithelial cells as well as to determine if other kinases involved in IFN-γ signal transduction, such as JAK-2, JAK-3, and TYK-2, are also activated by IL-10-IL-10R interaction. Future therapies for IBD will likely involve the use of cytokines to modulate inflammatory processes in the gastrointestinal tract. We believe that these studies will represent an attractive model to understand the complex interactions between cytokines regulating the Th1 and Th2 responses in the intestine.