Cells of the immune system, particularly T cells, are essential for protection against viral and bacterial infections and cancer. However, in some circumstances, for example in chronic infections or in growing tumors, they become dysfunctional. Yuri Pritykin (Computer Science/Lewis-Sigler Institute) and colleagues performed a systematic data-driven meta-analysis of T cells in cancer and infection. Their comprehensive atlas of T cell functional and dysfunctional states will help in further studies towards developing better cancer immunotherapies and strategies for treatment of chronic infections and autoimmune diseases. The study is published in Molecular Cell.