LMP1 expression in transgenic mouse derived cell lines. (A) LMP1 was immunoprecipitated from 300 μg of urea buffer-extracted proteins from seven PyLMP1 transgene-positive line 53 carcinoma cell lines and one transgene-negative cell line (as denoted 53.217neg) and 100 μg of protein from control cell lines: Raji (EBV +ve, containing 50-60 copies of EBV) and Ramos (EBV -ve), using the S12 antiserum. Immunoprecipitated proteins were separated by 10%SDS-PAGE and blotted alongside two total lysate (boiling mix extracted) controls, BL2B95-8 (EBV +ve) and BJAB (EBV -ve) (1 × 105 cells each). The blot was probed with anti-LMP1 antibody 1G6 followed by goat α-rat IgG HRP. The bands corresponding to LMP1 and the immunoglobulin heavy (H) and light (L) chains are indicated on the left. (B) Protein was extracted from B-cell lines 39.415 and 3959.48 with controls Raji and BJAB (the number of cells indicated below each track) using boiling mix and samples western blotted for LMP1 using IG6. The transgenic LMP1 (tgLMP1) is slightly smaller than Raji LMP1 (rLMP1) .