Murine RAW 264.7 cell line as an immune target: are we missing something?

The popular murine macrophage cell line, RAW 264.7, is often used to initially screen natural products for bioactivity and to predict their potential effect in vivo or on primary cells. The cell line response is considered to reflect the potential human de novo response, and is used to evaluate the effective bioactivity of the product. Here, we compared the cytokine response of RAW 264.7 cells to shark cartilage (SC) with that of human leukocytes to determine whether the cell line response was a reliable predictor of the cytokine response one can expect from similarly stimulated human primary cells. Results not only revealed significant differences in the nature and level of TNF alpha produced by cells in vitro, but also showed that while the primary cell response included an upregulation in the production of IL-1 beta such a response was absent in RAW 264.7 cells. This suggests that had we relied on RAW 264.7 cells alone to assess the cytokine-inducing capacity of SC, the comprehensive Th1 response (shown in an earlier study) induced by SC in primary cells, consisting of release of several proinflammatory cytokines and chemokines, would not have been revealed. We conclude, therefore, that assays using only RAW 264.7 cells to initially screen for and assess immune reactivity of test products will not necessarily provide a comprehensive picture of the immunomodulatory properties of the substance under investigation, and can in fact be misleading with regard to the overall bioactive potential of the substance on an initial screen.