Heterozygous TLR3 mutations in three unrelated IAV-ARDS patients. (A) Family pedigrees with TLR3 allele segregation. The black symbols indicate patients, and the bold vertical lines indicate healthy carriers of the mutant TLR3 allele. Healthy TLR3 WT relatives are indicated by white symbols. (B) Multiple sequence alignment across 19 vertebrate species. Both residues mutated in P1, P2, and P3 were highly conserved. (C) Predicted three-dimensional structure of the human TLR3 protein ectodomain. The residues affected by the two missense mutations found in IAV-ARDS patients are highlighted in magenta (P554S and P680L). The L360P mutation was previously identified in a patient with HSE (highlighted in violet). (D) Schematic diagram of the structure of the human TLR3 gene and protein, featuring the leader sequence (L), leucine-rich repeats (LRRs) of the ectodomain, transmembrane domain (TM), linker region (LR), and Toll/IL-1 receptor (TIR) domain. Roman numerals indicated the coding exons. Previously reported experimentally validated deleterious mutations found in HSE patients are shown in blue. The mutations found in the three children with severe influenza are shown in red (including the P554S mutation found in three previously reported and one unreported HSE patient).