Induction of immunoglobulin M (IgM), immunoglobulin G (IgG) subclasses and immunoglobulin A (IgA) on peritoneal cavity B-2 cells after treating with porin for 72 hr. B-2 cells were cultured with (open) or without (shaded) porin and analysed by flow cytometry for the expression of IgM, IgG1, IgG2a, IgG2b, IgG3 and IgA. Data shown are representative of three independent experiments.