The invention relates to the field of immunology. More specifically, it relates to methods and compositions to suppress the immune system, among other by interference with antigen-presenting molecules and T-cell activation. Provided is a composition for the prevention or treatment of a condition wherein suppression of T cell activation is desirable, comprising as an active ingredient an inositol phospholipid or a pharmaceutically acceptable salt thereof. Said condition can be an auto-immune disease, allergic disorder or chronic inflammatory disease, for example asthma, diabetes Type I, rheumatoid arthritis (RA) or inflammatory bowel disease (IBD). Also provided is a food item or food supplement having immunomodulating properties, comprising an effective amount of an inositol phospholipid.