Enhancement of Immunoglobulin Productivity of Human–Human Hybridoma HB4C5 Cells by Basic Proteins and Poly-basic Amino Acids

Immunoglobulin M productivity of a human-human hybridoma line, HB4C5, was enhanced by the addition of histones H1, H2A, and H2B in serum-free medium, which are lysine-rich histones. On the contrary arginine-rich histones, histone H3 and H4, did not stimulate immunoglobulin production at all. Another arginine-rich protein, protamine also did not significantly stimulate immunoglobulin production. These results suggested that there is a correlation between amino acid residues of basic proteins and stimulation of immunoglobulin production. In this connection, immunoglobulin production stimulating activities of poly-lysine and poly-arginine were investigated. Both poly-L-lysine and poly-D-lysine stimulated IgM productivity of the human-human hybridomas. These results show that the enhancing effect of lysine residues was derived from its physiochemical features. On the other hand, poly-L-arginine did not enhance the productivity.