Sustained localized expression of ligand for the activating NKG2D receptor impairs natural cytotoxicity in vivo and reduces tumor immunosurveillance (original) (raw)

Upregulation of the inducible gene products MICA (human) and Rae-1 (mouse) may promote tumor surveillance and autoimmunity by engaging the activating receptor NKG2D on natural killer (NK) cells and T cells. Nevertheless, sustained expression of MICA by tumors can also elicit NKG2D downregulation, perhaps indicating 'immunoevasion'. Investigating this paradox, we report here that constitutive Rae-1e transgene expression in normal epithelium elicited local and systemic NKG2D downregulation, generalized but reversible defects in NK cell-mediated cytotoxicity and mild CD8 + T cell defects. The extent of NKG2D downregulation correlated well with the incidence and progression of cutaneous carcinogenesis, emphasizing the utility of NKG2D as a marker of tumor resistance. Thus, NKG2D engagement is a natural mediator of immunosurveillance, which can be compromised by locally sustained ligand expression but potentially restored by innate immune activation.

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