Molecular diagnosis of ABMR with or without donor-specific antibody in kidney transplant biopsies: Differences in timing and intensity but similar mechanisms and outcomes

Abstract

We studied the clinical, histologic, and molecular features distinguishing DSA-negative from DSA-positive molecularly defined antibody-mediated rejection (mABMR). We analyzed mABMR biopsies with available DSA assessments from the INTERCOMEX study: 148 DSA-negative versus 248 DSA-positive, compared with 864 no rejection (excluding TCMR and Mixed). DSA-positivity varied with mABMR stage: early-stage (EABMR) 56%; fully developed (FABMR) 70%; and late-stage (LABMR) 58%. DSA-negative patients with mABMR were usually sensitized, 60% being HLA antibody-positive. Compared with DSA-positive mABMR, DSA-negative mABMR was more often C4d-negative; earlier by 1.5 years (average 2.4 vs. 3.9 years); and had lower ABMR activity and earlier stage in molecular and histology features. However, the top ABMR-associated transcripts were identical in DSA-negative versus DSA-positive mABMR, for example, NK-associated (e.g., KLRD1 and GZMB) and IFNG-inducible (e.g., PLA1A). Genome-wide class comparison between DSA-negative and DSA-positive mABMR showed no significant differences in transcript expression except those related to lower intensity and earlier time of DSA-negative ABMR. Three-year graft loss in DSA-negative mABMR was the same as DSA-positive mABMR, even after adjusting for ABMR stage. Thus, compared with DSA-positive mABMR, DSA-negative mABMR is on average earlier, less active, and more often C4d-negative but has similar graft loss, and genome-wide analysis suggests that it involves the same mechanisms. SUMMARY SENTENCE: In 398 kidney transplant biopsies with molecular antibody-mediated rejection, the 150 DSA-negative cases are earlier, less intense, and mostly C4d-negative, but use identical molecular mechanisms and have the same risk of graft loss as the 248 DSA-positive cases.

Keywords: basic (laboratory) research/science; biopsy; kidney transplantation/nephrology; microarray/gene array; rejection; rejection: antibody-mediated (ABMR).

FIGURE 1

Study design flowchart

FIGURE 2

Moving averages showing relationships between ABMR‐associated molecular and histologic features and time posttransplant in 464 archetype‐assigned mABMR biopsies. (A) Molecular classifier scores over time, (B) ABMR‐associated archetypes over time, and (C) ABMR‐associated histology features, DSA, and C4d over time. Moving averages (window size 150) were plotted by first sorting the biopsies by their time posttransplant, then plotting the mean of biopsies 1–150 y‐variable values against the mean of the biopsies 1–150 days posttransplant. The window is then slid to biopsies 2–151, 3–152, etc. with the process repeated. Consecutive window “bins” are created, and the moving averages calculated for each bin

FIGURE 3

Scatterplots showing probe set (A) fold change in DSA‐negative mABMR biopsies versus No rejection biopsies (y‐axis) and DSA‐positive mABMR biopsies versus No rejection biopsies (x‐axis); (B) p values for the same class comparisons; (C) fold change in DSA‐negative histologic ABMR biopsies versus histologic Normal/AKI biopsies (y‐axis) and DSA‐positive histologic ABMR biopsies versus histologic Normal/AKI biopsies (x‐axis); and (D) p values for the same class comparisons. Blue dashes show the 1:1 line in each plot

FIGURE 4

Kaplan–Meier curves comparing survival probabilities among biopsy groups in mABMR or in No rejection biopsies. One random biopsy per patient was selected for the analysis, and biopsies were not used if they did not have a valid follow‐up time or status. Survival probabilities are compared among (A) mABMR biopsy groups: EABMR, FABMR, and LABMR (N = 305); (B) DSA‐positive and DSA‐negative EABMR biopsies (N = 122); (C) DSA‐positive and DSA‐negative FABMR biopsies (N = 111); (D) DSA‐positive and DSA‐negative LABMR biopsies (N = 54); (E) DSA‐positive and DSA‐negative all‐ABMR biopsies (N = 268); and (F) DSA‐positive and DSA‐negative No rejection biopsies (N = 639)