Knockout mice: a paradigm shift in modern immunology

In the past decade, advances in genetic engineering and mouse knockout technology have transformed our understanding of the immune system. In particular, new perspectives on T-cell development, co-stimulation and activation have emerged from the study of single and multiple gene-knockout animals, as well as from conditional knockout and 'knock-in' mutants. Analysis of these animals has clarified important intracellular signalling pathways and has shed light on the regulatory mechanisms that govern normal immune responses and autoimmunity.