Agricultural by-productsis a rich source of dietary fibers including arabinoxylans, which is found mainly in water-insoluble form and reported to have immunomodulatory activities. We investiglatedwhether solublearabinoxylan (AX)-enriched byproducts alters macrophage activity.Agricultural by-products wereorally given to mice for 4 weeks. Peritoneal macrophages from mice were assayed for scavenger receptor expression, phagocytosis, and lipopolysaccharide (LPS)-stimulated responses. Serum levels of inflammatory cytokines were determined 1 hour after intraperitoneal injection of LPS. Agricultural by-productstreated mice showed a higher expression of SRA and CD36, accompanied by enhanced phagocytosis of latex beads, relative to control mice. Upon stimulation with LPS ex vivo, macrophages from the byproducts group showed lower levels of CD86 and CD40 at the surface protein level and lower production of NO, tumor necrosis factor (TNF)-α, and interleukin (IL)-6, compared with the control group. Theagricultural by-products group showed a decrease in serum levels of LPS-induced TNF-αand IL-6, while mice given crude byproducts, which was prepared without enzymatic hydrolysis, showed a reduction only in serum TNF-α,indicating that soluble arabinoxylans contributes to the immunomodulatory effect ofagricultural by-products. Our data present evidence that soluble arabinoxylan-enriched agricultural by-products can be an immune enhancing functional food.