Clone REAL497 recognizes the mouse Ly-49I antigen, a single-pass type II C-type lectin-like membrane glycoprotein also known as Ly-49 inhibitory receptor I. The Ly-49 receptors are encoded by a family of highly polymorphic and polygenic genes within the mouse NK gene complex which includes genes that encode both inhibitory and activating Ly-49 receptors. Ly-49 receptors recognize MHC-I and MHC-I-like proteins on normal as well as altered cells. They are described as being expressed on both the developing and mature natural killer (NK) cells. The inhibitory Ly-49 receptors are involved in NK cell education, a process in which NK cells acquire function and tolerance toward cells that express “self-MHC-I”. On the other hand, the activating Ly-49 receptors recognize altered cells expressing activating ligands. Ly-49 receptors have been described on multiple NK cell subsets, such as uterine NK and memory NK cells, as well as NKT cells, dendritic cells, plasmacytoid dendritic cells, macrophages, neutrophils, and cells of the adaptive immune system, such as activated T cells and regulatory CD8

T cells. Ly-49I is an inhibitory receptor capable of down-modulating proliferation, IFN-γ response, and cytotoxic activity in cells that express it.