B cell precursor growth-promoting activity. Purification and characterization of a growth factor active on lymphocyte precursors.

TLDR

Using a biological assay system, the authors established an SV40‑transfected stromal cell line that produced lymphopoietin 1 (LP‑1), which they purified from the culture supernatant. LP‑1 is a 25‑kDa protein that stimulates proliferation and maintenance of B‑cell precursors, binds specific receptors, and exhibits a specific activity of ~4 × 10⁶ U/mg with half‑maximal activity at 10⁻¹³ M after a 10⁷‑fold purification with 35 % recovery.

Abstract

We have used a biological assay system we developed to biochemically purify a previously uncharacterized murine lymphopoietic growth factor designated lymphopoietin 1 (LP-1). This factor is capable of stimulating the proliferation and extended maintenance of precursor cells of the B lineage. A stromal cell line producing LP-1 was established after transfection of primary stromal cultures with a plasmid encoding the transforming genes of SV40. This factor was purified to a single 25-kD species from the culture supernatant of an adherent stromal cell line. This material acts on immature lymphocytes, it binds to specific receptors on cells, and is distinct from previously described hematopoietic factors. LP-1 has been purified some 10(7)-fold with an overall recovery of 35%. The purified protein exhibits a specific activity of approximately 4 X 10(6) U/micrograms of protein and is active at a half-maximal concentration of 10(-13) M.