An intron gene trap cassette, containing a loxP site, Engailed 2 splice acceptor/STOP (En-2/stp), IRES, lacZ, downstream element (DSE) and floxed neo cassette, was targeted to intron 1. This allele is both a knock-out and conditional-ready allele, as it can be reverted back to wild-type expression through cre-mediated recombination. Western blot analysis confirmed the absence of protein expression in bone marrow derived macrophage stimulated with (S)-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-Cys-(S)-Ser-(S)-Lys4-OH (P3C). (J:188968)