The immune system is comprised of diverse cell types that work together to protect the host from infection and maintain tissue homeostasis. To achieve this complex balance, extracellular cues determine highly specific epigenetic landscapes and transcriptional profiles of each immune cell subtype. New evidence indicates that long non-coding RNAs (lncRNAs) play critical roles in epigenetic and transcriptional regulation in mammals. Here we identify the lncRNA Morrbid, and examine its role in immune function. In Chapter 2, we assess the function of Morrbid at homeostasis and describe its role in finely tuning the lifespan of short-lived myeloid cells. In Chapter 3, we examine Morrbid under inflammatory conditions and illustrate its role in restraining CD8 T cell responses following viral infection. These data demonstrate that lncRNAs can function as highly cell-type specific effectors of extracellular cues to control immunological processes that require rapid and strict regulation.