CD70 represents the human ligand for CD27

The recently identified CD27 ligand (L) Is a type II transmembranemolecule with significant structural homology to tumor necrosisfactor (TNF)-, TNF-ß, lymphotoxin ß, CO40L,and CD30L. Using a CD27L specific mAb we examined the tissuedistribution of the molecule, and found Its expression to berestricted to B cells in occasional germinal centers, stromalcells in the thymic medulla, and scattered T cells in tonsils,skin and gut. As the limited expression of CD27L closely resembledthe reported distribution of the activation antigen CD70, wetested whether CD70 represents the human CD27L. CD70 mAb werefound to react with CD27L-expressing transfected mouse fibroblasts.Moreover a number of CD70 mAb could specifically interfere withthe cellular binding of CD27L mAb. Thus, CD70 Is Identical tothe human CD27L.