Ly49Q positively regulates type I IFN production by plasmacytoid dendritic cells in an immunoreceptor tyrosine-based inhibitory motif-dependent manner.

Plasmacytoid dendritic cells (pDC) are the major producers of type I IFN during the initial immune response to viral infection. Ly49Q, a C-type lectin-like receptor specific for MHC-I, possesses a cytoplasmic ITIM and is highly expressed on murine pDC. Using Ly49Q-deficient mice, we show that, regardless of strain background, this receptor is required for maximum IFN-α production by pDC.