Molecular and biological characterization of a ligand for CD27 defines a new family of cytokines with homology to tumor necrosis factor

CD27 is a surface antigen found on T and B cells that has homology to a family of molecules including the receptors for tumor necrosis factor (TNF) and nerve growth factor. A cDNA encoding a ligand for CD27 was isolated by a direct-expression cloning strategy using a fusion protein composed of the extracellular domain of CD27 linked to the constant domain of a human immunoglobulin G1 molecule as a probe. The predicted protein product is a type II transmembrane protein whose gene maps to 19p13 and that shows homology to TNF and the ligand for CD40. Biological characterization indicates that the cloned ligand induces the proliferation of costimulated T cells and enhances the generation of cytolytic T cells.