▁was ▁the ▁first ▁to ▁confirm ▁in ▁large ▁clin ical ▁studies ▁the ▁effic acy ▁of ▁new ▁imm unos upp ress ive ▁dru gs ▁after ▁pan cre as ▁trans plant ation . ▁Gru ess ner ' s ▁basic - s cience ▁research ▁has ▁focused ▁on ▁different ▁techniques ▁of ▁don or ▁cell ▁augment ation ▁for ▁toler ance ▁induction ▁after ▁trans plant ation ▁and ▁on ▁different ▁re jection ▁patterns ▁in ▁single ▁versus ▁combined ▁trans pl ants . ▁In ▁ 2 0 1 5 , ▁he ▁and ▁his ▁team ▁showed ▁that ▁ 2 5 ▁years ▁of ▁organ ▁trans plant ation ▁in ▁the ▁U . S . ▁saved ▁ 2 . 2 ▁million ▁years ▁of ▁life ▁in ▁patients ▁with ▁end - stage ▁organ ▁failure . ▁ ▁Biography ▁and ▁career ▁Gru ess ner ▁was ▁born ▁in ▁ 1 9 5 7 ▁in ▁Main z , ▁Germany ▁and ▁completed ▁medical ▁school ▁at ▁the ▁Johannes ▁G uten berg ▁University . ▁In ▁ 1 9 8 3 , ▁he ▁was ▁awarded ▁“ sum ma ▁cum ▁la ude ” ▁for ▁his ▁doctor al ▁th esis . ▁After ▁his ▁res iden cy , ▁he ▁completed ▁a ▁fellow ship ▁in ▁trans plant ation ▁imm un ology ▁at ▁the ▁University ▁of ▁Minnesota . ▁In ▁ 1 9 9 1 , ▁Gru ess ner ▁completed ▁his ▁professor ial ▁th esis ▁( “ H abil itation ”, ▁the ▁German ▁Ph . D . ▁equivalent ) ▁at ▁Philipp s ▁University ▁of ▁Mar burg ▁in ▁Mar burg , ▁Germany . ▁ ▁In ▁ 1 9 9 1 , ▁Gru ess ner