We then infected L2 cells (a rat lung epithelial cell line) with a wild-type, Δbcr4, Δbcr4+bcr4-FL-FLAG, Δbcr4+bcr4Δ169-173-FLAG, Δbcr4+bcr4Δ164-173-FLAG, or Δbcr4+bcr4Δ159-173-FLAG strain at a multiplicity of infection (MOI) of 50 for 1 h and measured the amounts of lactate dehydrogenase (LDH) released into the culture medium as an index of cytotoxicity. Here, BCRP4 is linked to infection.