Functional and structural characterization of P40, a mouse glycoprotein with T-cell growth factor activity.

Antigen-independent cell lines were derived from mouse helper T-cell clones by culture in autologous supernatant obtained after stimulation with concanavalin A. A factor, termed P40, supporting the growth of these lines was purified and characterized as a basic 32- to 39-kDa single-chain glycoprotein functionally distinct from previously identified T-cell growth factors and apparently unrelated structurally to any known protein. Of a number of cell lines, only helper T cells responded to P40, and this response was not mediated by either interleukin 2 or interleukin 4.