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 wherein the inositol phispholipid is a diacylglycerol phosphotidyl inositol. Said condition can be an auto-immune disease, for example psoriasis.
