Isotype switching in anti-immunoglobulin-activated B lymphoblasts: Differential requirements for interleukin 4 and other lymphokines to elicit membrane vs. secreted IgG sub(1)

Anti-immunoglobulin (Ig)-activated B lymphoblasts, prepared by culturing high-density B cells with anti-Ig-Sepharose for 48 h, can be induced to secrete IgM and IgG sub(1) by a mixture of T cell-derived lymphokines containing interleukin (IL) 4. In this study we have examined the conditions required for lymphokine-mediated induction of IgG sub(1) secretion and membrane (m)IgG sub(1) expression in B lymphoblasts. The results suggest that LPS and IL 4 are sufficient to commit B lymphoblasts to mIgG sub(1) expression, but that additional signals provided by T cell-derived lymphokines are required to elicit IgG sub(1) secretion.