CCL19 and viral infectious disease: The lymphatic endothelial cells of Cluster 12 strongly expressed Tspan6, Mrc1, Ccl21a (all described above) as well as Bst2 (antiviral), Arrb2 (involved in multiple signaling pathways including that of CCL19), Ptx3 (positive regulation of innate response to pathogens) and Serinc3 (resistance to viral infection).