The relevance of adenosine receptor signaling has been well established for numerous physiological and pathological processes, and adenosine receptors are being studied as potential drug targets. Adenosine production from extracellular ATP by the ectoenzymes CD39 and CD73 on the surface of cells has been shown to be an important source of adenosine for adenosine receptor signaling in various types of immune cells. Recently, an alternative, CD39-independent, pathway of extracellular adenosine production from NAD+ via the ectoenzymes CD38, CD203a, and CD73 has been described in Jurkat T cells. We investigated the expression of both pathways in several macrophage subsets as well as the potential autocrine effects of extracellular adenosine produced by them. We identified GM-CSF- and M-CSF-differentiated macrophages treated by interferon (IFN) and lipopolysaccharide (LPS) as the main cell types expressing ectoenzymes of both pathways and selected them for further analysis.^ ^By blocking ectoenzymes of either pathway, we explored the influence of extracellular adenosine production on macrophage function. Our findings support the notion that classical adenosine production might be a relevant factor in inducing an antiinflammatory phenotype in M-CSF- differentiated, IFN+LPS-treated macrophages. In particular, CD39 inhibition led to a decrease in IL-10 and an increase in proinflammatory cytokines. Blocking the alternative pathway in these cells, however, reduced the concentration of both IL-10 and proinflammatory cytokines, suggesting that the pathway might not be functional in these macrophages or function in an unexpected manner. Similarly, blocking either CD39, CD38, or, to a lesser degree, CD73 seemed to induce a reduction in IL-10 as well as IL-1, IL-6, TNF, IL-12, and IL-23 in GM-CSF-differentiated, IFN+LPS-treated macrophages.^ Interestingly, we found that the influence of CD73 inhibition on cytokine profiles and expression patterns of surface markers was only weak in either cell type. Furthermore, we identified a potential mechanism of cross-talk between the two adenosine production pathways in the sense that inhibition of CD39 led to a marked decrease in CD38 surface expression. As a final assessment of macrophage behavior upon inhibition of adenosine production by either pathway, we cocultured pre-treated macrophages with CD4+ T cells and subsequently performed T cell proliferation assays. We did not observe any major effect of blocking macrophage adenosine-producing ectoenzymes on their ability to stimulate CD4+ T cell proliferation.