The invention provides isolated nucleic acids molecules, designated SLIC-1 nucleic acid molecules, which encode novel P-selectin glycoprotein ligand (PSGL-1) binding molecules. The invention also provides antisense nucleic acid molecules, recombinant expression vectors containing SLIC-1 nucleic acid molecules, host cells into which the expression vectors have been introduced, and nonhuman transgenic animals in which a SLIC-1 gene has been introduced or disrupted. The invention still further provides isolated SLIC-1 proteins, fusion proteins, antigenic peptides and anti-SLIC-1 antibodies. Diagnostic methods utilizing compositions of the invention are also provided.