BF and SPF mice demonstrate a different gastrointestinal microbiome composition and priming with BF fecal matter restores TRALI-susceptibility in SPF mice. (A) Phylogenetic tree of BF mice, which are susceptible to TRALI (BF – TRALI); SPF mice, which do not suffer from TRALI (SPF – NO TRALI); and BF mice treated with antibiotics, which are also resistant to TRALI (BF – antibiotics NO TRALI). (B-C) Gastrointestinal bacterial heat maps and pie charts on family level, respectively. (D-E) Gastrointestinal bacterial heat maps on genus and species levels, respectively. (F-G) Data from BF fecal transfer into SPF mice: (A) lung W/D weight ratios, (B) pulmonary PMN numbers upon CD4⁺ T-cell depletion and anti-MHC class I antibody (clones 34-1-2s and AF6-88.5.5.3) infusion into indicated mouse groups. Heat map row numbers 1-3, BF mice upon arrival; 4-6, BF mice after 1 week of housing; 7-9, SPF mice upon arrival; and 10-12, SPF mice after 1 week of housing. (F-G) Analyzed by a 1-tailed unpaired Student t test and represent combinatorial data from 2 experiments. Each dot represents 1 mouse; error bars represent SD. *P < .05, **P < .01.