GRADE-2 CELLULAR HEART REJECTION - DOES IT EXIST

According to the International Society for Heart and Lung Transplantat ion, a single focus of lymphocytic infiltration associated with myocyt e injury in a cardiac allograft endomyocardial biopsy is focal moderat e cellular rejection (Grade 2). We reviewed 115 endomyocardial biopsy specimens that were completely negative (n = 17), had a Quilty A (n = 17) or Quilty B (n = 46) lesion, or had a lesion fulfilling the criter ia of grade 2 rejection (n = 35). By studying step sections (mean = 18 ) or sections stained for elastic tissue and collagen, we showed conti nuity of the focus of grade 2 rejection with the endocardium in 32 of 35 cases; these results justify reclassification of these foci as Quil ty B lesions, which are defined as endocardial infiltrates that encroa ch on the underlying myocardium and that may be associated with myocyt e injury but are not generally considered to represent acute rejection . Immunohistochemical staining for T and B lymphocytes and histiocytes showed similar patterns in deeper zones of Quilty B lesions and lesio ns initially regarded as grade 2 rejection. Normal hemodynamics were o bserved with 16 of 17 completely negative biopsy specimens, 16 of 17 Q uilty A biopsy specimens, 46 of 46 Quilty B biopsy specimens, and 35 o f 35 grade 2 rejection biopsy specimens. No grade 2 rejection was trea ted; only 1 biopsy specimen progressed to grade 3A rejection in a subs equent biopsy 2 months later. Most, if not all, cases of grade 2 cellu lar rejection can be shown to be Quilty B lesions, are not associated with hemodynamic abnormalities, and do not require augmented immunosup pression. If our findings are confirmed by others, the current classif ication of heart transplant rejection may require modification.