Humans are exposed to harmful pathogens and a wide range of noxious substances every day. The immune system reacts to, and destroys, these pathogens and harmful substances. The immune system is composed of innate and adaptive immunity, which liaise to protect the host and maintain health. Foods, especially cereals, have been reported to modulate the immune response. Arabinoxylans are nonstarch polysaccharides that have been shown to possess immune-modulatory activities. This review article discusses the fundamentals of the immune system and provides an overview of the immunomodulatory potential of arabinoxylans in conjunction with their structural characteristics and proposed similarities with lipopolysaccharides.