CD40LG and plasma cell myeloma: In J[μ1]L cells (Sitia et al, 1987, 1990), IgM secreting transfectants of the J558L myeloma that express B1-8-derived μ chain as well as endogenous L and J chains, μ and L chains efficiently assembled into intermediate complexes (μL and μ2L2) and secretion-competent polymers recognized by anti-μ and anti-L antibodies (lanes 5 and 9, Pols).