The present invention pertains to novel antibodies capable of binding to CD26, as well as to their use as a medicament. Moreover, the present invention provides antibodies for use in treating and/or preventing Graft-versus-Host Disease (GvHD), for use in treating Aplastic Anemia and/or for use in promoting engraftment after haematopoietic stem cell transplantation. Furthermore, the present invention provides pharmaceutical compositions comprising at least one antibody of the present invention, as well as provides a kit of parts.