Multimeric compounds that bind to P-Selectin Glycoprotein 1 (PSGL-1) on thesurface of T cells or natural killer (NK) cells can be used to induce T cellor NK cell depletion and/or to induce T cell or NK cell apoptosis. Themultimeric compounds and methods of the invention can be used to controlunwanted T cell-or NK cell-mediated immune responses in conditions such asinflammatory diseases, autoimmune diseases, transplant rejection, and allergicdiseases.