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Updated: Feb 18, 2026
Investigating the Immunological Mechanisms Underlying Organ Transplant Rejection
Published on: August 20, 2007
Review: The transcripts associated with organ allograft rejection
Philip F Halloran1,2, Jeffery M Venner1, Katelynn S Madill-Thomsen1,2
1Alberta Transplant Applied Genomics Centre, Edmonton, AB, Canada.
Abstract:
The molecular mechanisms operating in human organ transplant rejection are best inferred from the mRNAs expressed in biopsies because the corresponding proteins often have low expression and short half-lives, while small non-coding RNAs lack specificity. Associations should be characterized in a population that rigorously identifies T cell-mediated (TCMR) and antibody-mediated rejection (ABMR). This is best achieved in kidney transplant biopsies, but the results are generalizable to heart, lung, or liver transplants. Associations can be universal (all rejection), TCMR-selective, or ABMR-selective, with universal being strongest and ABMR-selective weakest. Top universal transcripts are IFNG-inducible (eg, CXCL11 IDO1, WARS) or shared by effector T cells (ETCs) and NK cells (eg, KLRD1, CCL4). TCMR-selective transcripts are expressed in activated ETCs (eg, CTLA4, IFNG), activated (eg, ADAMDEC1), or IFNG-induced macrophages (eg, ANKRD22). ABMR-selective transcripts are expressed in NK cells (eg, FGFBP2, GNLY) and endothelial cells (eg, ROBO4, DARC). Transcript associations are highly reproducible between biopsy sets when the same rejection definitions, case mix, algorithm, and technology are applied, but exact ranks will vary. Previously published rejection-associated transcripts resemble universal and TCMR-selective transcripts due to incomplete representation of ABMR. Rejection-associated transcripts are never completely rejection-specific because they are shared with the stereotyped response-to-injury and innate immunity.
Insights
Messenger RNA (mRNA) profiles in organ transplant biopsies reveal key molecular mechanisms of rejection. Identifying specific mRNA signatures helps differentiate T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR) for improved diagnostics.
Area of Science:
- Molecular biology and immunology of organ transplantation.
- Biomarker discovery for transplant rejection.
Background:
- Organ transplant rejection mechanisms are complex, with proteins having low expression and short half-lives, and small non-coding RNAs lacking specificity.
- Accurate classification of T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR) is crucial for understanding rejection pathways.
Purpose of the Study:
- To characterize mRNA expression profiles associated with different types of organ transplant rejection.
- To identify universal, TCMR-selective, and ABMR-selective molecular signatures in kidney transplant biopsies, generalizable to other organs.
Main Methods:
- Analysis of mRNA expression in kidney transplant biopsies with rigorous identification of TCMR and ABMR.
- Classification of transcript associations into universal, TCMR-selective, and ABMR-selective categories based on expression patterns.
Main Results:
- Identified distinct mRNA signatures for universal rejection (e.g., IFNG-inducible, shared by T cells and NK cells), TCMR (e.g., activated T cells, macrophages), and ABMR (e.g., NK cells, endothelial cells).
- Demonstrated high reproducibility of transcript associations across biopsy sets when standardized methods are applied.
- Noted that previously identified rejection transcripts primarily reflected universal and TCMR patterns due to underrepresentation of ABMR.
Conclusions:
- mRNA profiling in biopsies provides robust insights into organ transplant rejection mechanisms.
- Specific transcriptomic signatures can differentiate between TCMR and ABMR, aiding in precise diagnosis and potentially guiding treatment strategies.
- Rejection-associated transcripts are influenced by broader responses like injury and innate immunity, highlighting the complexity of molecular signatures.
