Transcriptomic profiling of transplant glomerulopathy to reveal a novel T-cell dominant subclass

Kidney transplant biopsies showing transplant glomerulopathy (cg > 0) and microvascular inflammation (MVI) in the absence of C4d staining and DSAs do not fulfill the criteria for chronic active antibody-mediated rejection (CA-AMR) diagnosis or any other Banff category. In this multicenter intercontinental study including 36 cases, we compared, among other types of data, the transcriptomic profiles of 14 KTx biopsies classified as cg+MVI DSA-/C4d- with 22 classified as CA-AMR DSA+/C4d+ through novel transcriptomic analysis using the NanoString B-HOT panel. Due to lack of tissue, one sample was excluded from the transcriptomic analysis. In our analysis, nineteen genes were differentially expressed between the two study groups. Samples diagnosed with CA-AMR DSA+/C4d+ showed a higher transcriptomic cell type scores for macrophages in an environment characterized by increased expression of complement-related genes (i.e., C5AR1) and higher activity of angiogenesis, IFTA, CA-AMR, and DSA-related pathways when compared to samples diagnosed with cg+MVI DSA-/C4d-. Samples diagnosed with cg+MVI DSA-/C4d- displayed a higher activity of the T-cell receptor and B-cell associated transcripts. These results were coherent with those from our 5-plex immunofluorescence orthogonal analyses showing higher abundance of innate immune cells in the interstitium of CA-AMR DSA+/C4d+ samples when compared to cg+MVI DSA-/C4d- samples and a higher glomerular abundance of pan-T-cells in cg+MVI DSA-/C4d- samples when compared to CA-AMR DSA+/C4d+ samples. Here we show that using novel multiomic techniques, KTx biopsies with cg+MVI DSA-/C4d- have a prominent T-cell presence and activity, putting forward the possibility that these represent a more T-cell-dominant phenotype. This retrospective multicenter intercontinental study included a highly selected population of KTx recipients. KTx biopsy samples were retrieved from the archives of the Department of Pathology, ErasmusMC, Rotterdam, the Netherlands (ErasmusMC-cases, n = 19) and the Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, United States of America (MGH-cases, n = 17). Thirty-six transplant recipients who fulfilled the first two diagnostic criteria for CA-AMR were retrospectively included in this study (n = 36). Twenty-two patients were classified as CA-AMR DSA+/C4d+, as they had positive C4d staining of ptcs (Banff C4d lesion score ≥ 1) and showed circulating DSAs. The remaining 14 patients were classified as cg+MVI DSA-/C4d- as they did not have C4d positive staining of ptcs (Banff C4d lesion score = 0) and had no circulating DSAs. Due to lack of tissue, one sample was excluded from the transcriptomic analysis.