Humoral rejection in cardiac transplantation: risk factors, hemodynamic consequences and relationship to transplant coronary artery disease.

Background: Acute cellular rejection is the mechanism of most immune-related injury in cardiac transplant recipients. However, antibody-mediated humoral rejection (HR) has also been implicated as an important clinical entity following orthotopic heart transplantation. Humoral rejection has been reported to play a role in graft dysfunction in the early post-transplant period, and to be a risk factor for the development of transplant coronary artery disease. Some involved in transplantation pathology doubt the existence of clinically significant humoral rejection in cardiac allografts. Those who recognize its existence disagree on its possible role in graft dysfunction or graft coronary artery disease. In this study, we report clinical features of patients with the pathologic diagnosis of HR at our institution since July 1997, when we began systematic surveillance for humoral rejection.

Methods: We reviewed medical records of patients with the pathologic diagnosis of HR without concurrent cellular rejection between July 1997 and January 2001. Diagnosis was based on routine histology ("swollen cells" distending capillaries, interstitial edema and hemorrhage) and immunofluorescence (capillary deposition of immunoglobulin and complement with HLA-DR positivity), or immunoperoxidase staining of paraffin-embedded tissue (numerous CD68-positive macrophages and fewer swollen endothelial cells distending capillaries).

Results: A total of 44 patients (4 to 74 years old) showed evidence of HR without concurrent cellular rejection at autopsy or on one or more biopsies. Although females comprised only 26% of our transplant population, 23 patients (52%) with HR were female. A positive peri-operative flow cytometry T-cell crossmatch was observed in 32% of HR patients compared with 12% of controls (p = 0.02). Hemodynamic compromise consisting of shock, hypotension, decreased cardiac output/index and/or a rise in capillary wedge or pulmonary artery pressure was observed in 47% of patients at the time of diagnosis of HR. Six patients (5 females) died (14% mortality) with evidence of HR at or just before autopsy, 6 days to 16 months after transplantation. The incidence of transplant coronary artery disease was 10% greater at 1 year, and 36% greater at 5 years, in patients with HR when compared with non-HR patients.

Conclusions: Humoral rejection was associated with acute hemodynamic compromise in 47% of patients, and was the direct cause of death in 6 patients (13%). Humoral rejection is a clinicopathologic entity with a high incidence in women and is associated with acute hemodynamic compromise, accelerated transplant coronary artery disease and death.