Production of an Immunoglobulin-Binding Factor (IBF) by Antigen-Stimulated Lymph Node Lymphocytes

Abstract

Lymph node lymphocytes from rats immunized with a guinea pig encephalitogenic protein (GEProt) were incubated in vitro with the immunizing antigen in a serum-free medium. They released a factor which had the property to combine with IgG antibodies complexed with antigen, but not IgM antibodies, inducing hemagglutination of IgG-sensitized erythrocytes and protecting IgG-sensitized erythrocytes, but not IgM-sensitized erythrocytes from complement-induced hemolysis. A similar activity was found in supernatants from mixed leukocyte cultures between allogenic mouse strains. This factor was named immunoglobulin-binding factor (IBF). IBF was separated in rat from migration inhibitory factor, blastogenic factor, and lymphotoxin upon column fractionation techniques. IBF activity was found in fractions of about 150,000 m.w. and with a pH of about 6.30.