LYSOZYME STIMULATES IMMUNOGLOBULIN PRODUCTION BY HUMAN-HUMAN HYBRIDOMA AND HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

Lysozyme [EC 3.2.1.17] derived from hen egg white stimulated immunoglo bulin production by human-human hybridoma, HB4C5 cells producing human lung cancer specific monoclonal IgM. IgM production by HB4C5 cells wa s enhanced more than 13-fold by the addition of lysozyme at 380 mu g/m l in a serum-free medium. The immunoglobulin production stimulating ef fect of lysozyme was observed immediately after inoculation and mainta ined for 5 days. Lysozyme enhanced immunoglobulin production by the hy bridoma line without growth promotion. This enzyme also accelerated Ig M and IgG production of human peripheral blood lymphocytes 5.3-fold an d 2.3-fold, respectively. These results suggest that lysozyme stimulat es immunoglobuling production of not only specific hybridoma line, but also non-specific immunoglobulin producers. However, although the enz ymatic activity of lysozyme was almost lost by heat-treatment at 100 d egrees C for 30 min, the IPSF activity was retained. This fact suggest s that IPSF activity of lysozyme does not come from its enzymatic acti vity or reaction products. All these findings clearly indicate that ly sozyme has a novel function as an immunoglobulin production stimulatin g factor.