Transgenic inducible MHC I overexpression in mouse alveolar type 2 cells.

The major histocompatibility complex class I (MHC I) is crucial in adaptive immunity, enabling CD8 + T cells to detect and eliminate infected and cancerous cells. Recent studies have uncovered significant variability in MHC I expression across tissues, challenging the traditional belief of uniform expression. Lung epithelial cells (LECs) express meager amounts of MHC I, which preserves the lung epithelium from excessive inflammation but renders it more susceptible to cancer and infection. Despite MHC I overexpression in various immunopathologies, its precise role in disease initiation or progression remains unclear due to the absence of suitable in vivo models for studying MHC I overexpression. This study introduces a novel mouse model with targeted surface MHC I upregulation. Leveraging a conditional Cre-lox system, we augmented Nlrc5 expression to specifically upregulate MHC I in alveolar type 2 (AT2) LECs, known for their low basal expression of MHC I and significant overexpression in disease. Our model demonstrated a rapid and sustained tenfold increase in MHC I surface expression persisting for up to a year without triggering pathology or inflammation. Comprehensive characterization and validation of this model indicated that MHC I overexpression does not serve as a primary initiator of respiratory diseases under steady-state conditions and shows a therapeutic window for increasing MHC I without significant damage to the lung epithelium. This adaptable model offers insights into the effects of tissue-specific MHC I regulation and presents new avenues for therapeutic development.