REG3A and graft versus host disease: In addition, as stated earlier, it was proposed that regenerating islet-derived 3-a (reg3a), released from Paneth cells, was a potential plasma biomarker for lower GI GvHD (63), Paneth cell damage contributes to loss of antimicrobial peptides and accelerates the loss of microbial diversity in GvHD, a major risk factor of treatment-related mortality (80, 81).