Ecalectin as a T cell-derived eosinophil chemoattractant.

In our previous papers, we have shown that human T cells produce a unique eosinophil chemotactic factor (ECF), termed Ecalectin, with a molecular weight of about 30-50 kD during interaction with BALL-1 (a B cell line) extracts, antigen or mitogen. A 1.6-kB cDNA was isolated from a human T cell-derived expression library that encodes Ecalectin. Ecalectin is a 36-kD protein consisting of 323 amino acids based on its deduced amino acid sequence. Ecalectin was found to be a variant of human galectin-9, a member of the growing family of animal lectins exhibiting affinity for beta-galactosides. Recombinant Ecalectin, expressed in COS cells, exhibited potent ECF activity in vitro and in vivo in a dose-dependent manner but not chemotactic activity for neutrophils, lymphocytes, or monocytes. The finding that the Ecalectin transcript is present in various lymphatic tissues and that its expression increases substantially in antigen-activated peripheral blood mononuclear cells suggests that Ecalectin is an important T cell-derived regulator of eosinophil recruitment in allergic reaction sites.