Recently, we described a murine helper T cell-derived molecule with T cell growth factor activity that is functionally and structurally distinct from IL-2, IL-4, and other known growth factors. This molecule, designated P40, was identified as a glycoprotein capable of supporting antigen-independent growth of certain helper T cell clones. Here, we report the cloning and expression of a cDNA for this new growth factor. The predicted mature protein is a cationic cysteine-rich polypeptide of 14 kD without significant homology to previously sequenced proteins.
Functional and structural characterization of P40, a mouse glycoprotein with T-cell growth factor activity.