PTPN22 and acute lymphoblastic leukemia: PTPN22 is supposed to be located in the cytoplasm of T-cells and interacts with many signaling molecules, such as Lck, ZAP70, Csk, and Vav, thereby attenuating TCR signals.8 Juxtaposition of promoter and enhancer components of TCR genes with transcription factor genes throughout VDJ recombination is among the cytogenetic changes inflicting T-ALL.