Activating Ly-49 NK receptors: Central role in cytokine and chemokine production

In an attempt to understand potential novel functions of receptors in vivo, we evaluated gene expression after cross-linking the activating Ly-49D mou se NK receptor. Gene expression was evaluated using a mouse GEM 2 microarra y chip (Incyte Genomics, St. Louis, MO). Each chip displays a total of 8734 elements. The strongly induced genes fell into two categories: 1) soluble factors and 2) apoptotic genes. The majority of the strongly induced mRNAs as analyzed by microarray hybridization were chemokine genes. RNase protect ion assays and chemokine protein production analysis validated the microarr ay results, as cross-linking the Ly-49D mouse NK receptor induced high leve ls of IFN-gamma, lymphotactin, macrophage-inflammatory protein (MIP)1 alpha , and MIP1 beta. This gene expression was specific because other chemokines were not induced by anti-Ly-49D receptors. In addition, a series of pharma cological inhibitors were used to identify the key signaling pathways invol ved in the cellular response. The primary Ly-49D signaling for IFN-gamma pr oduction is predominately mediated through Src kinase pathways involving me mbrane proximal events, whereas MIP1 alpha and MIP1 beta gene induction is more complex and may involve multiple biochemical pathways. Thus, we conclu de that a primary role for the activating NK receptors in vivo may be to tr igger soluble factor production and regulation of the immune response. This would place NK cells and their activating Ly-49 receptors as important ini tiators of microbial immunity and key elements of the innate immune system. The Journal of Immunology, 2001.