Methods of treating, inhibiting and/or preventing instant blood-mediated inflammatory reaction (IBMIR) comprise administering, to a subject, a dextran sulfate characterized by a number average molecular weight (Mn) as measured by nuclear magnetic resonance (NMR) spectroscopy within an interval of 1850 and 3500 Da； an average sulfate number per glucose unit within an interval of 2.5 and 3.0； and an average sulfation of C2 position in the glucose units of said dextran sulfate of at least 90%, or a salt of such a dextran sulfate.
