Antibody mediated rejection in lung allograft biopsies is not well defined from a morphologic or immunohistochemical aspect. Many centers routinely run immunohistochemistry for C4d as it has shown to be significant in other organs transplants, however, there are no criteria for interpretation and there is a growing concern that C4d in the lung may not be significant. We investigated 85 patients who underwent lung allograft transbronchial biopsies who were tested for donor-specific antibodies (DSA) by Luminex and stained with C4d by immunohistochemistry. Interstitial capillary staining was scored as <1% negative, 1-10% minimal, 10-60% focal, and >50% diffuse. DSA values were counted as positive if greater than 1,000 mean fluorescence intensity (MFI). Our analysis showed that any staining in interstitial capillaries with C4d higher than 1% is associated with DSA in circulation, both Class I and Class II (DSA Class I and II OR 1.2, DSA Class I OR 1.39, DSA Class II OR 1.16). There was not a linear correlation between percentage of C4d in interstitial capillaries and DSA MFI. This study supports the concept that the detection of any positive staining in interstitial capillaries by C4d immunoperoxidase is potentially relevant for the presence of donor specific antibodies and antibody mediated rejected in the allograft. However, having a higher percentage of C4d does not necessarily correlate with a higher MFI of DSA.

CITATION INFORMATION: Butt Y, Gokaslan T, Kaza V, Torres F, Torrealba J. C4d Immunohistochemistry in Lung Allograft Interstitial Capillaries Lacks Linear Correlation with Donor Specific Antibodies, yet It Is Still Diagnostically Relevant. Am J Transplant. 2017;17 (suppl 3).

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