Mixtures of hyaluronan (HA), chondroitin sulfate (CS)-A and CS-C oligosaccharides were generated through the enzymatic digestion of the polysaccharides with either mammalian hyaluronidase or bacterial HA lyase or chondroitinase. Compared to mammalian enzymes, bacterial enzymes hydrolyze the polysaccharides through a different mechanism yielding chemically distinct sets of oligosaccharides. Peripheral leukocytes and a human monocytic cell line were exposed to these oligosaccharides and the amount of interleukin-12 released by the cells was measured. For all types of oligosaccharide tested, we found that the amount of interleukin-12 induced by oligosaccharides generated with bacterial enzyme was significantly lower than the amount of interleukin-12 induced by oligosaccharides generated with mammalian enzyme. In addition, we observed that CS oligosaccharides generated with bacterial enzyme were capable of reducing the lipopolysaccharide-induced interleukin-12 production in macrophages. Our results indicate that HA or CS oligosaccharides generated with mammalian enzymes might possess pro-inflammatory potential, while HA or CS oligosaccharides generated with bacterial enzymes might possess non- or anti-inflammatory properties. The implications of our findings in view of the ongoing investigation of the potential therapeutic benefits of HA and CS in arthritis or other inflammatory pathologies are discussed.