Dietary lectins and the immune response

Human food contains lectins, and lectins are therefore consumed in their native form when foods are eaten raw or when foods containing lectins that are heat stable are eaten. Because lectins are resistant to digestion, they reach the small intestine in an active form. Some lectins are toxic, giving rise to diarrhea, and have on a few occasions been found to cause death.

Lectins have many biological activities as they bind to carbohydrate on various cells. Many receptors are membrane- integrated glycoproteins and function as receptors for hormones and cytokines or are involved in cell–cell recognition. By binding to these receptors, lectins may mimic a natural ligand of a receptor or inhibit binding of a natural ligand and thereby evoke a variety of systemic and local effects, such as cell division and growth, cell maturation, and cell death.

The use of lectins in immunology as polyclonal activators has long been recognized as their binding to receptors on immune cells induces mitogenesis. Dietary lectins may be immunomodulatory and affect both the innate and the adaptive immune response. Some lectins are able to induce a lectin-specific immune response, while others function as adjuvants, giving rise to an immune response against coadministered proteins.

Inflammatory cytokine production, oral tolerance, production of antibodies, and apoptosis are some of the immune functions influenced by dietary lectins. Dietary lectins might be involved in induction of diseases with an immunological background, such as allergy and autoimmune diseases. To exploit fully the effect of lectins on the immune function, further studies are required, especially in relation to diseases potentially related to the ingestion of lectins.

Moreover, the potential use of lectins in cancer therapy and in drug and vaccine delivery systems clearly emphasize that further studies on the influence of lectins on the immune system are required.