Disclosed herein are methods of increasing the proliferation of non-tumorigenic B cells. The methods involve administering PCDGF and optionally other B cells stimulators (e.g., IgM, LPS) to B cells resulting in an increase in B cell proliferation. The methods of the invention can be used, for example, to establish B cells lines, to sort B cells from a mixed population of cells, or to activate resting B cells.