One hundred twenty-five kilodalton CLA⁺ glycoprotein comigrates with core-2-decorated CD43, not known selectin ligands. Aliquots of CLA⁺-cultured T-cell lysate were subjected to SDS-PAGE under nonreducing conditions, transferred to PVDF membranes, and immunostained for CLA (mAb HECA-452), PSGL-1 (mAb PL-1), CD62L (mAb DREG56), CD44 (mAb HERMES), CD43 core protein (mAb 1G10), CD43 sialic acid-dependent epitope (mAb L60), and a CD43 core-2-branched O-glycan-dependent epitope (mAb 1D4). PSGL-1 migrates in nonreducing SDS-PAGE as both a 240-kDa dimer band and a 140-kDa monomer band. The HECA-425-reactive bands at 240 kDa and 140 kDa correspond to CLA-decorated PSGL-1 dimer and monomer, respectively. The HECA-452-reactive band at 125 kDa comigrates with high-molecular-weight CD43 and not PSGL-1, CD62L, or CD44. Blots for CD43 L60 epitope and 1D4 epitope indicate that 125-kDa CD43 is decorated with both sialic acid and core-2-branched carbohydrate. Anti-PSGL-1-specific mAbs PL-2, KPL-1, and PSL-275 showed reactivity identical to PL-1 (not shown). The 125-kDa band and 115-kDa band seen with mAb 1G10 are also observed with additional CD43 antibodies to the core protein (MT-1 and DF-T1; not shown). Isotype control blots show no bands (not shown). High-range and full-range molecular weight markers are run in flanking lanes as shown. Molecular weights in kDa for the high-range markers are shown to the left of each blot row.