Chitooligosaccharides from the shrimp chitosan hydrolysate induces differentiation of murine RAW264.7 macrophages into dendritic-like cells

•Oligomixture and LMWC with different Mw were isolated from chitosan hydrolysate.•Both LMWC and oligomixture inhibited the superoxide production in RAW264.7 cells.•Oligomixture, but not LMWC, induced DC-like morphological changes in RAW264.7 cells.•Oligomixture induced G0/G1 phase cell cycle arrest in RAW264.7 cells.•Oligomixture promoted the expression of mature DC-associated cell markers. Dendritic cells and macrophages are professional antigen-presenting cells that activate T-cell-mediated immune responses. A water-soluble hydrolysate with immunomodulatory activity was obtained by cellulase degradation of shrimp chitosan. This chitosan hydrolysate was further separated into a low-molecular-weight chitosan (LMWC) and achitooligosaccharide mixture (oligomixture). In this study, the effects of these three chitosanolytic samples on the induction of murine RAW264.7 macrophages into dentritic-like cells were investigated. Both the chitosan hydrolysate and oligomixture but not the LMWC increased cell size, induced dendritic morphological changes and caused G0/G1 phase cell cycle arrest in RAW264.7 cells. The oligomixture markedly suppressed the superoxide production of RAW264.7 cells and stimulated the phagocytic activity and expression of dendritic cell surface markers (B7.1, B7.2, and CD40). These findings demonstrate that an oligomixture (chitooligosaccharides) isolated from chitosan hydrolysate can induce differentiation of RAW264.7 macrophages into dendritic-like cells, and consequently, enhances both the cell-mediated and humoral immune responses.