A plant extract which enhances the plating efficiency of lymphoid cell lines and enhances the survival of normal lymphoid cells in vitro.

A water soluble extract from the bark of the Samoan medicinal plant Alphitonia zizyphoides A. Gray (Rhamnaceae), enhances the plating efficiency in vitro of lymphoid cell lines as well as the survival of bone marrow cells and normal T and B lymphocytes. Furthermore, the inclusion of bark-extract into culture media enhances the cloning efficiency of a T-hybridoma cell line by more than 30 times at otherwise unsuitably low serum concentrations, but does not completely substitute for serum. The enhanced growth of a B-cell hybridoma is also paralleled by an increased production of monoclonal antibodies in cultures containing low cell densities.