Signalling through serine/threonine kinases is a key mechanism that regulates immune cell development, activation and effector functions. An emerging theme is that serine kinases do not act in isolation, but function in a complex overlapping network. Understanding the molecular targets of serine kinases as well as their links to other serine kinases is key to advancing our understanding of the intracellular signalling pathways that link immune receptors with the gene transcriptional programs that control the immune system in vivo.