This book provides an essential overview of the role of phosphoinositide-3-phosphate kinase (PI3K) isoforms in modulating the function of immune system cells and their involvement in disease. PI3K is a family of kinases involved in basic cellular processes such as proliferation, migration and cell death. Recent work has highlighted the multiple roles of PI3K classes and subunits and their involvement in the immune response to the body's own and foreign antigens and diseases such as cancer and autoimmunity. This book offers a detailed introduction to the biology of the three PI3K classes, followed by an extensive discussion of the diverse roles of AKT and PI3K isoforms in immune cells. Based on this knowledge, it subsequently explains in more detail how specific isoforms are connected to immune-mediated diseases. The book concludes by highlighting the latest advances in the production of isoform-specific inhibitors and their use in various human diseases. This book is intended as a reference guide for students and researchers interested in the multifaceted aspects of PI3K biology.