*Purpose: Rejection remains a serious problem in the pediatric transplant population. Early detection remains a challenge; furthermore, the changes in immune makeup which accompany rejection remain poorly understood. We developed a mass cytometry-based approach to construct detailed immune profiles from peripheral blood mononuclear cells (PBMCs) of pediatric transplant recipients with stable graft function or with biopsy-proven rejection. These data will further our understanding of the pathogenesis of rejection and facilitate novel approaches to identifying and treating rejection.

*Methods: We constructed a 37-marker mass cytometry panel that allows interrogation of T-cell, B-cell, monocyte/macrophage, and NK-cell phenotypes in PBMCs. We obtained patient samples from the Clinical Trials of Organ Transplantation in Children (CTOT-C)-06 bank. Blood samples were collected prior to, every 3 months post transplant for the first 24 months and every 6 months thereafter. Using our mass cytometry panel, we constructed immune profiles from PBMCs of children who had biopsy-proven rejection within the 30-day period following sample collection and compared them to immune profiles constructed from patients with stable graft function in the 12-month period surrounding sample collection. We then used a combination of dimensionality-reduction algorithms and unsupervised clustering methods to identify differences between those with biopsy-proven rejection and stable graft function.

*Results: 80 children were selected for profiling, 40 with biopsy-proven rejection and 40 with stable graft function. 36% were heart transplant recipients, 16% were kidney transplant recipients, 45% were liver transplant recipients, and 3% were intestinal transplant recipients. We demonstrated that each of the markers in our panel is both sensitive and specific for the populations of interest. We further demonstrated that this approach is sensitive enough to detect changes in immune composition elicited by transient exposure to various cytokines. Our findings suggest greater diversity in T- and NK-cell phenotype than has been previously appreciated using conventional approaches.

*Conclusions: Use of mass cytometry to construct detailed immune profiles from the peripheral blood of pediatric transplant recipients will elucidate populations critical for the development of rejection and may form the basis for new minimally-invasive approaches to its detection and treatment.

« Back to 2020 American Transplant Congress