Purpose To examine myocardial inflammatory (MI) burden and phenotype of intravascular (IV) cells in EMBs with pathologic (p)AMR (Berry JHLT2011;30:601); to correlate both with pAMR grade, capillary C4d deposition and DSA status. Methods and Materials HE grade 1: n=6) or no pAMR (n=31). EMBs also showing acute cellular rejection ≥ 2R were excluded. Sections were stained for CD68, CD3, CD20 and CD138. Positive IV and interstitial mononuclear cells (MI burden) were counted in 5 microscopic fields at X40 magnification (area: .225 mm 2 ) by 6 pathologists blinded to the diagnosis. Results were correlated with pAMR grade, C4d-positivity and DSA status. Results [Table 1] Conclusions Mean MI burden correlates with pAMR grade, C4d positivity, and DSA positivity. In pAMR equivalent numbers of IV T lymphocytes and macrophages were seen. CD68 antibody staining alone is not sufficient to characterize IV cells in pAMR. Total burden inflammatory cells Total IV inflammatory cells CD 68 IV cell CD3 IV cells CD20 IV cells CD 138 IV cell Mean (SD) Mean (SD) Mean (SD) Mean (SD) Mean (SD) Mean (SD) pAMR neg(n=31) 83.0 (61.3)* 8.1 (9.1)* 3.3 (3.8)* 4.0 (6.3)* 0.3 (1.0)** 0.4 (1.2)*** pAMR-positive/ suspicious (n=34) 329.1 (187.1)* 83.8 (64.3)* 37.4 (44.9)* 41.2 (36.9)* 2.4 (4.3)** 3.1 (8.2)*** C4d-negative (n=36) 96.4 (71.9)° 17.1 (27.1)° 4.9 (8.3)° 11.4 (23.6)° 0.3 (1.0)°° 0.3 (1.1)°°° C4d-positive (n=29) 354.8 (188.6)° 85.7 (68.3)° 41.3 (47.1)° 38.3 (36.6)° 2.8 (4.5)°° 3.7 (8.8)°°° DSA-negative (n=30) 104.1 (108.6)^ 14.3 (26.6)^ 6.9 (11.7)^ 6.4 (15.6)^ 0.7 (2.1)^^ 0.2 (0.6)^^^ DSA-positive (n=35) 304.0 (192.7)^ 76.3 (66.3)^ 33.3 (45.6)^ 38.0 (36.5)^ 2.0 (4.0)^^ 3.1 (8.1)^^^ pAMR(-) vs pAMR(+) *p
