The natural immune system is a subject of great research interest because it provides powerful and flexible information processing capabilities as a complex adaptive system. This paper describes our extensible framework, named iNet, for building artificial immune systems, particularly artificial immune networks, which has been used in several of our projects developing biologically-inspired intelligent applications. We describe the iNet architecture, its design principles and features, highlighting its versatility and component reusability. We also describe an autonomous decentralized network application built with iNet as a sample use case for showing how to use it.