Phagocytosis of N-acetyl-d-glucosamine particles, a Th1 adjuvant, by RAW 264.7 cells results in MAPK activation and TNF-α, but not IL-10, production

A practical and highly effective Th1 adjuvant should induce Th1 cytokines (IL-12, IL-18, and TNF-α) but not the Th2 cytokine IL-10, an inhibitor of Th1 responses. In this study, phagocytosis of N-acetyl-d-glucosamine polymer (chitin) particles by RAW 264.7 cells, a murine macrophage-like cell line, resulted in phosphorylation of MAPK (p38, Erk 1/2, and JNK), and production of relatively high levels of TNF-α and COX-2 with increased PGE2 release. Similar results were observed in response to oligonucleotides with CpG motifs, mycobacterial components and endotoxin. However, these bacterial components also induced a large amount of IL-10. Chitin particles, in contrast, failed to induce detectable levels of IL-10, although the production of high levels of PGE2 and TNF-α and the activation of MAPK’s are potentially positive signals for IL-10 production. Thus, our results indicate that chitin particles act as a unique Th1 adjuvant for macrophages without inducing increased production of IL-10.