Universal CNK-UT Therapy for Refractory aGVHD

"Dose Escalation (Single Ascending Dose Study, SAD): During SAD study stage, the participants will be intravenous infused with CNK-UT cells (3×10\^7 CNK+ cells/kg)with a3 +3 design to determine the maximum tolerated dose. During single ascending dose (SAD) study stage, the participants will receive a single dose of CNK-UT cells before the DLT observation period (21 days). If the participants do not experience DLT, they will be able to enter a multiple ascending dose (MAD) study stage.~Dose Expansion (multiple ascending dose study, MAD): During MAD study stage, the participants will receive multiple doses of CNK-UT cells(6-10×10\^7 CNK+ cells/kg). The dosage and frequency of drug administration in the dose expansion stage can be adjusted and determined according to the SAD study."