Lymphotoxin is an important T cell-derived growth factor for human B cells.

Two different assays for B cell growth factors (BCGF) and an antibody against lymphotoxin were used to show that the presence of lymphotoxin in conditioned media derived from normal activated T cells and in a partially purified BCGF accounts for a substantial portion of their B cell growth-promoting activity. A competitive binding assay confirmed the presence of significant amounts of lymphotoxin in the partially purified BCGF. Recombinant lymphotoxin enhanced the proliferation of activated B cells and augmented B cell proliferation and immunoglobulin secretion induced by interleukin-2.