Identification of an interleukin HP1-like plasmacytoma growth factor produced by L cells in response to viral infection.

We have recently purified and partially sequenced a new T cell-derived lymphokine with growth factor activity for B cell hybridomas and plasmacytomas, which we named interleukin HP1 (HP1). Here we show that, in response to viral infection or after treatment with poly(rI).poly(rC), L cells produce a factor that is capable of supporting the in vitro growth and survival of HP1-dependent cell lines. Serologic and structural evidence is presented in favor of the identity between the fibroblast factor and HP1, demonstrating that non-T cells can make HP1-related molecules

Purification and NH2-terminal amino acid sequence of a T-cell-derived lymphokine with growth-factor activity for B-cell hybridomas

A T-cell-derived lymphokine was identified by its ability to support the growth of a subset of B-cell hybridomas. Hybrids that failed to survive in the absence of this molecule represented a major proportion of rat-mouse hybridomas but were very rare among mouse-mouse B-cell hybrids. Stable factor-dependent B-cell hybridomas were used to monitor the purification of the growth factor from the supernatant of a clonotypically stimulated mouse helper T-cell clone. Sequential fractionation using gel filtration, anion-exchange chromatography, and reversed-phase HPLC resolved the factor from other B-cell growth factors and yielded a single-chain protein characterized by a major charge (pI = 5-7) and molecular mass (22- to 29-kDa) heterogeneity, probably due to variations in glycosylation. The NH2-terminal amino acid sequence of this protein, which is active on B-cell hybridomas in the 0.1 pM range, showed no significant homology with that of known lymphokines. Because the purified factor also supported the growth and survival in vitro of murine plasmacytomas (to be published elsewhere), it was provisionally designated interleukin-HP1 (where H stands for hybridoma and P stands for plasmacytoma)