Organization of the TNF superfamily genes within the paralogous regions present on chromosomes 1, 6, and 19. Left panel: Diagram of the human chromosome 19p13.3 region containing the LIGHT genomic locus. Middle panel: Distribution of TNF paralogous superfamily gene clusters arranged from centromere to telomere. Arrows indicate gene transcriptional orientation, and solid blocks represent exons. LIGHT is 7.78 kb from C3 and about 79 kb from CD27L. CD27L is about 235 kb from 4-1BBL. FasL is separated from AITRL by 374 kb, while AITRL and OX40L are 134 kb apart. TNF is 2.9 kb from LTβ and 1.3 kb from LTα. Right panel: activities of the TNF-related ligands on T cells.