Immunomodulatory effects of proanthocyanidin A-1 derived in vitro from Rhododendron spiciferum

Abstract The objective of this study was to evaluate the immunomodulatory effects of proanthocyanidin A-1 (PAA-1) from leaves of Rhododendron spiciferum ( Ericaceae ). In vitro tests showed that PAA-1 stimulated cell proliferation of splenocytes and peritoneal macrophages significantly enhanced the cytotoxicity of natural killer (NK) cells and increased CD4 + and CD8 + cell populations. PAA-1 also regulated the expression of Th1- and Th2-related cytokines. Moreover, this study showed that PAA-1 exhibited a significant effect on NBT dye reduction and lysosomal enzyme activity responses in macrophages, indicating effective phagocytic activation. These results revealed that PAA-1 exhibits immunomodulatory activity without a clear dose response.