Preferential endocardial residence of B-cells in the "Quilty effect" of human heart allografts: immunohistochemical distinction from rejection.

Endocardial infiltrates (EI) are a common and often problematic observation in endomyocardial biopsy specimens (EMBs) from patients receiving cyclosporine immunosuppression following cardiac transplant. Histologic and immunohistologic findings in 23 EMBs from 19 patients and 15 autopsy or explanted allografts demonstrated EIs to be rich in B lymphocytes (871/mm2) compared to T-lymphocytes (803/mm2). Macrophages also demonstrated an endocardial preference over deeper myocardium. In contrast, T-lymphocytes outnumbered B-lymphocytes in deeper myocardium (mean 44/mm2 versus 22/mm2) especially when rejection was present. In allograft specimens, the overall number of typical nodular EIs or percent length of endocardial involvement by EI did not correlate with the presence or absence of myocardial rejection at autopsy or explant but were related to implant duration (r = +0.63, p less than 0.01) and number of previous rejection episodes. The number of thin, nondiscrete endocardial infiltrates was greater in hearts with any myocardial rejection or inflammation present. No relationship was observed between EIs present in either EMB or allografts and the cumulative or mean dose or mean serum level of cyclosporine. Thus, a distinct morphologic and immunohistologic profile distinguishes EIs from acute rejection.