This absence of LEC PD-L1 may contribute to phenotypes resulting from LEC MHC-II loss, as evidenced in PD-1 deficient mice42 with relevant pneumonia history (Fig. 6e) showing greater memory CD4+ TRM cell plasticity (Fig. 6f and Supplementary Fig. 18) and multipotency (Fig. 6g) in their lungs but not their blood, akin to MHC-IIΔEpi mice. This evidence concerns the gene CD4 and susceptibility to pneumonia measurement.