BACKGROUND: Antibody mediated rejection has now been defined as a pathology definition. The new ISHLT pathology grading scale was recently published by Barry et al. JHLT 2012. Pathology AMR is now graded as 0 (no AMR), AMR 1 (suspicious), AMR 2 (positive), and AMR 3 (severe). pAMR 2 and pAMR 3 have been suggested to require therapy. It is unknown as to the natural history of pAMR 1. Therefore, we assessed the progression of pAMR 1 in subsequent biopsies.

METHODS: Between January 2010 and March 2012, we evaluated 58 heart transplant patients who were found by our single pathologist to have pAMR 1. Subsequent biopsies were recorded along with treatment if administered. Six month outcome of survival and concomitant or subsequent cellular rejection were also recorded.

RESULTS: In the 96 pAMR episodes, pAMR 1 resolved in 65% (pAMR resolved), persisted in 24% (pAMR persisted), and progressed to pAMR 2/3 (pAMR progressed) in 9%. Subsequent clinical events for the pAMR resolved, pAMR persisted, and pAMR progressed groups was significant for less freedom from subsequent 6 month cellular rejection in the pAMR persisted and pAMR progressed groups vs pAMR resolved group (see table).

CONCLUSION: pAMR 1 progresses to more severe AMR in 9% of cases. If pAMR 1 does not resolve, the risk for acute cellular rejection is increased. Therefore, pAMR 1 must be monitored carefully.

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