Transcriptional activity of the CXCL13 promoter cloned from LW and YL pigs. A Luciferase activities of pGL3-CXCL13LW and pGL3-CXCL13YL in PK15 cells at 24 h post-transfection. Luciferase activities of pGL3-CXCL13LW (B) or pGL3-CXCL13YL (C) in PK15 cells with and without PCV2 infection. PCV2-infected groups (pGL3-CXCL13LW-i and pGL3-CXCL13YL-i) were inoculated with PCV2 at an MOI of 0.1 TCID50 and PCV2-uninfected groups (pGL3-CXCL13LW-u and pGL3-CXCL13YL-u) were treated with equivalent PK15 cell lysate at 6 h post-transfection. Luciferase activity was detected at 0, 12, 24, 36, and 48 hpi. D Detailed delineation of the promoter regions of the porcine CXCL13 gene by 5′ deletion analysis. The left panel shows a schematic diagram for firefly luciferase reporter constructs containing the indicated genomic sequences upstream of CXCL13. The right panel shows the luciferase activity of the corresponding deletion construct. At least three separate experiments were performed with each plasmid DNA preparation. Data are represented as the mean value ± SE of three experiments. * and *** indicate significance at the P value threshold levels of 0.05 and 0.001, respectively.