Background: The root of Cynanchum auriculatum Royle ex Wight has been traditionally used as a folk medicine in the eastern Asia. Objectives: In this study, we explored the immune-enhancing effect of the high-molecular weight fraction of C. auriculatum (CAHF) root extracts in RAW 264.7 macrophages and cyclophosphamide (CYP)-induced immune-suppressed mice.
Materials and Methods: To obtain the CAHF, ultrafiltration was performed using 30-kDa molecular weight cutoff polyethersulfone membranes in a cross-flow microfiltration system. In vitro and in vivo experiments were performed to evaluate the immunostimulatory effects of CAHF. Results: CAHF increased the production of nitric oxide and immunostimulatory cytokines (interleukin-6 and tumor necrosis factor-α) in recombinant interferon-γ primed macrophages. In addition, the phagocytic activity of macrophage cells was enhanced by CAHF. Furthermore, CAHF treatment markedly restored the decreased body weight, immune organs (spleen and thymus) weight, natural killer cell activity, and T- and B-lymphocyte proliferation in CYP-induced immune-suppressed mice. Conclusion: These results suggest that CAHF is an effective immunostimulatory agent.