ZAP70 and colitis: However, the PTP-mediated effect of TULA-1 on T-cell signaling is consistent with the following findings: the effect of dKO on ZAP-70 and ZAP-70-mediated signaling is significantly higher than that of TULA-2 sKO [24], TULA-1 has a detectable PTP activity [20,24], and TULA-1 and TULA-2 sKOs exhibit comparable effects on ZAP-70 phosphorylation in T cells from mice with a chemically induced colitis [36];