Purification and partial characterization of human intracellular B cell growth factor

In the present report a protocol for the purification of an intracellular protein, exhibiting BCGF activity has been described. This protein is obtained from lectin stimulated human peripheral blood mononuclear cells and has been previously shown to be present only in the cytosolic extract of normal human T-lymphocytes. The isoelectric point (pI) of the purified protein is 6.3, as determined by both sucrose gradient isoelectric focusing and chromatofocusing. The molecular weight of the chromatofocused protein, determined by SDS-PAGE, is 60 kD. Thirty-three percent of the BCGF activity contained in the initial crude extract is recovered as a homogenously purified protein, with an estimated specific activity of 10(5) U/mg.