White bamboo is the swollen stem of Zizania latifolia parasitized by the smut fungus Ustilago esculenta. Five samples of galls were harvested at different stages of swelling, along with young seedlings of Z. latifolia and isolated colonies of U. esculenta. The inhibition capacity of boiling water or 50% ethanol extracts on NO release by RAW264 cells, which was stimulated with lipopolysaccharide, was evaluated as anti-inflammatory activity, while the NO induction capacity was evaluated as immunostimulatory activity. Total polyphenol (TPP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity were also measured. The anti-inflammatory effect, as well as TPP and DPPH, was comprehensively detected in the ethanol extracts. The immunostimulating activity was observed in the boiled extracts at different levels, depending on the swelling stage, and was especially high in the top (apical) part. These data may indicate that functional components could be dynamically induced by interactions between Z. latifolia and U. esculenta.