ATTRACTIN (DPPT-L), A MEMBER OF THE CUB FAMILY OF CELL-ADHESION AND GUIDANCE PROTEINS, IS SECRETED BY ACTIVATED HUMAN T-LYMPHOCYTES AND MODULATES IMMUNE CELL-INTERACTIONS

Attractin is a normal human serum glycoprotein of 175 kDa that is rapi dly expressed on activated T cells and released extracellularly after 45-72 hr, We have cloned attractin and find that, as in its natural se rum form, it mediates the spreading of monocytes that become the focus for the clustering of nonproliferating T lymphocytes, There are two m RNA species with hematopoietic tissue-specific expression that code fo r a 134-kDa protein with a putative serine protease catalytic serine, four EGF-Iilie motifs, a CUB domain, a C type lectin domain, and a dom ain homologous with the ligand-binding region of the common gamma cyto kine chain. Except for the latter two domains, the overall structure s hares high homology with the Caenorhabditis elegans F33C8.1 protein, s uggesting that attractin has evolved new domains and functions in para llel with the development of cell-mediated immunity.