Selective loss of MHCII expression in pIV^−/− mice.

Mice with a targeted deletion of CIITA pIV lack IFNγ-induced MHCII expression on nonhematopoietic cells and constitutive MHCII expression on cortical thymic epithelial cells (cTECs) and mTECs. Professional APCs retain IFNγ-induced CIITA expression via pI (microglia, macrophages) and constitutive expression via pI (DCs) and pIII (B cells, DCs).