Abstract: Methods of inhibiting mammalian platelet release of CD40 ligand, thromboxanes, or prostaglandin E2, or surface expression of CD40 ligand that involve contacting mammalian platelets with an effective amount of a PPAR? agonist, an RXR agonist, or a combination thereof. As a consequence of inhibiting CD40 ligand and thromboxane release, the present invention allows for inhibition of thrombus fon-nation by (or clotting activities of) activated platelets, as well as treating or preventing CD40 ligand-mediated conditions and/or thromboxane-mediated conditions. Use of PPAR? agonist, RXR agonist, and/or inducers of PPAR? agonist in preparing a stored blood product, and for diagnostic testing of patient samples is also disclosed.