CXCR3 and respiratory tract infectious disorder: While the underlying mechanisms responsible for the progression from respiratory infection to CLAD is poorly understood, we postulate that any infectious pathogen can trigger a deleterious cycle of cell damage, aberrant Type 1 immune response with recruitment of injurious mononuclear cells to the allograft through CXCR3/CXCL9 biology, causing further cell damage and eventual fibroproliferation that ultimately leads to CLAD.