Ciita-iCre Mouse

The CIITA (Class II Major Histocompatibility Complex Transactivator) gene acts as the "master control switch" for the adaptive immune system. It does not bind DNA directly but functions as a transcriptional coactivator, encoding the CIITA protein, which assembles a multi-protein complex (the enhanceosome) to initiate the expression of MHC class II genes. While constitutively expressed in professional antigen-presenting cells like B cells and dendritic cells, its expression can be induced by interferon-gamma (IFN-γ) in almost any nucleated cell type, such as epithelial or endothelial cells ^[1]. Mutations in CIITA lead to Bare Lymphocyte Syndrome Type II (BLS II), a severe combined immunodeficiency characterized by the absence of MHC II molecules, resulting in a failure of CD4+ T cell development and a compromised immune response ^[2].

Ciita-iCre mice were generated using gene editing technology to replace the TGA stop codon with the P2A-iCre cassette. Under the control of the Ciita gene's regulatory elements, the iCre recombinase (a codon-optimized Cre recombinase) is expressed. When Ciita-iCre mice are crossed with mice containing loxP sites, Cre recombinase-mediated recombination between loxP sites is expected to occur in the antigen-presenting cells (APCs) and Ciita-positive cells in the offspring.