Schematic structure genomic organization of PD-1 and PD-L1 gene. The bars represent the exons (EX) and the lines represent introns. The blue bars are exons of the PD-1 gene which encode different regions of the PD-1 protein, including: L-region (EX1), hydrophilic-region (EX2), V-likedomain (EX2), connecting-region (EX3), transmembrane-region (EX3), C-like-domain (EX3), intracytoplasmic regions (EX4) and cytoplasmic-region (EX5) . The yellow bars are exons of the PD-L1 gene which encode different regions of the PD-L1 protein, including: Immunoglobulin V-set domain (EX2),immunoglobulin constant domain (EX3), transmembrane region (EX4-EX7); diagonal line filled black and white bar represent the exons which do not express post transcriptional alternative splicing [NM_014143.3]. The numbers under the exons are the number of nucleotides corresponding to size of each exon.