Review: The transcripts associated with organ allograft rejection.

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.