Original Clinical Science
Pathologic classification of antibody-mediated rejection correlates with donor-specific antibodies and endothelial cell activation

https://doi.org/10.1016/j.healun.2013.05.012Get rights and content

Background

Humoral immune responses during heart transplantation may result in antibody-mediated rejection (AMR), which is now taken into account on endomyocardial biopsy (EMB) specimens and ranked according to the pathologic AMR (pAMR) grades of the International Society for Heart and Lung Transplantation classification. This classification might benefit from new immunohistological markers and validation by others biomarkers, namely donor-specific antibodies (DSA).

Methods

From the 293 protocol EMBs performed in 113 patients in our institution during a 1-year period for this prospective study, 280 EMB specimens were available with both histology and immunohistochemistry. C4d and labeling of intravascular cells by cluster of differentiation (CD) 68 were performed on paraffin sections. Available sera (n = 150) concomitant of EMB specimens were tested for the presence of DSA. All of the pAMR+ EMB specimens, along with a set of randomized pAMR0 EMB specimens, were immunolabeled for mammalian target of rapamycin (mTOR) effectors, phosphorylated 70 S6-kinase (p70S6K) and phosphorylated S6 ribosomal protein (pS6RP).

Results

AMR was diagnosed in 37 EMB specimens (13.2%): 1 pAMR1(I+), 27 pAMR1(H+), and 9 pAMR2. The proportion of DSA-positive EMB varied according to the pAMR grade, with pAMR0, pAMR1(H+), and pAMR2 EMB presenting 17.6%, 77.3%, and 100% of DSA-positivity, respectively. Among the 30 pAMR+ specimens with available DSA testing and the 30 pAMR0 randomized specimens, mTOR pathway immunohistochemistry showed endothelial cell positivity for p70S6K in 17 pAMR+ EMB specimens (56.7%) and in 1 pAMR0 EMB specimen (3.3%). pS6RP was detected in 8 pAMR+ EMB specimens (26.7%) and in 1 pAMR0 EMB specimen (3.3%).

Conclusions

p70S6K and pS6RP immunohistochemistry afford new markers of AMR on EMB specimens because their expression is correlated with microcirculation inflammation and DSA. The correlation of DSA with pAMR grade suggests that this grading system is valid.

Section snippets

EMB and patients

A total of 293 protocol EMBs were performed in 113 patients in our institution between October 1, 2009, and September 30, 2010. Two patients were excluded because of inadequate EMB specimens. Patient characteristics of the 111 recipients included in the study are given in Table 1. All recipients in our center undergo a routine protocol EMB according to a pre-determined tapering schedule with early and late assessments of graft histology. In our practice, a protocol EMB is performed in a

Histopathologic characteristics and pAMR classification

Histopathology results are summarized in Table 2 and illustrated in Figure 2. MI (Figure 2A), defined by the presence of mononuclear cells within capillaries, was present in 12.9% of the EMB specimens and observed in early and late (> 2 years) EMB specimens. C4d (Figure 2B) and CD68 (Figure 2C) were positive in 0.7% and 3.6% of the samples, respectively. According to the pAMR classification, pAMR0, pAMR1(I+), pAMR1(H+), and pAMR2 were diagnosed in 86.8%, 0.4%, 9.6%, and 3.2% of the EMB samples,

Discussion

The present study evaluates the pathologic classification of AMR in heart transplantation in a prospective, non-selected series of protocol EMB specimens with concomitant DSA testing. Our main result is that the pAMR classification correlates with DSA and with in situ markers of endothelial cell activation through the mTOR pathway.

Our study gives insight into the incidence of AMR in a non-selected series of heart recipients. Herein, pAMR1 and pAMR2 specimens represented 9.3% and 3.6% of the

Disclosure statement

The authors thank the staff from Hôpital Européen Georges-Pompidou, Chantal Mandet, Nicole Pfister, and Sophie Maillard, for technical assistance.

This work was supported by the Agence de la Biomédecine grant 2012 to P.B. A.L. and J.P. D.V.H. are members of the Centaure group.

Part of this study was presented as an oral communication at the Thirty-first Annual Meeting and Scientific Sessions of the International Society for Heart and Lung Transplantation, San Diego, California, April 13–16, 2011,

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