PSGL-1 can be immunoprecipitated from WEHI-3B cells with anti–PSGL-1 MoAb 2PH1. WEHI-3B cells were surface-biotinylated and subjected to immunoprecipitations with IgG from a rabbit nonimmune serum (control 1), affinity-purified antibodies from a rabbit antiserum against mouse PSGL-1 (α-PSGL-1), MoAb 2PH1 (2PH1), and an isotype-matched control rat antibody (control 2). Proteins were electrophoresed on an 8% polyacrylamide gel under reducing conditions. The front of the gel is marked by an arrow on the left, and molecular mass markers (in kD) are also indicated on the left.