While organ transplants can enhance and extend the duration of recipients’ life, improved understanding of the interaction between transplanted tissue and the immune system can improve outcomes and reduce the rate of rejections. With up to 40% of kidney transplants failing within 10 years of transplantation, researchers are searching for ways to interrogate mechanisms of rejection and improve post-transplantation care for kidney transplant recipients.
Given the variety of immune cells and their functions, characterization of immune response is complex. Analytical techniques that average signals, such as cytokine secretion or protein expression, across many cells will miss key functional differences. Single-cell analysis gives researchers a better idea of how each cell contributes to the immune response, allowing for a more in-depth insight into immune function. By measuring up to 32 functional proteins from each cell, IsoPlexis’ Single-Cell Secretome platform provides the ability to functionally phenotype immune cells and interrogate molecular mechanisms of immune response.
Single-Cell Polyfunctionality is Associated with Transplant Rejection
In a paper recently published in the Journal of American Society of Nephrology, researchers sought to identify the immune factors that can lead to humoral rejection of kidney grafts. Subsets of CD8+ memory T cells called terminally differentiated effector memory cells, or TEMRA cells, have previously been shown to be pathogenic in other types of immune-related disorders, including lupus, scleroderma, and kidney transplant failure. The researchers used a number of techniques to investigate how CD8+ memory T cells can contribute to humoral rejection.
To characterize CD8+ T cell function, the researchers used IsoPlexis’ Single-Cell Secretome platform to measure secreted functional proteins of cells isolated from blood of kidney transplant recipients with and without humoral rejection. Compared to recipients with normal biopsies, CD8+ T cells from recipients with humoral rejection had significantly more polyfunctional cells, or cells secreting 2 or more cytokines, after CD3/CD28 stimulation. Polyfunctional cells have previously been identified as drivers of immune response, indicating a possible mechanism for rejection.
The authors further analyzed the cytokine secretions of the stimulated CD8+ T cells and discovered an increase in pro-inflammatory (IFN-γ, TNF-α, MIP-1α, and MIP-1β) and cytotoxic (granzyme B and perforin) cytokines from recipients with humoral rejection. The combined increase of these cytokine subsets led researchers to believe that TEMRA CD8+ T cells were contributing to the immune response, potentially indicating TEMRA CD8+ T cell dysregulation could lead to humoral rejection.
Additional experiments revealed that TEMRA CD8+ T cells from humoral rejection samples had increased cytotoxic and migratory activity compared to other T cell subsets, leading researchers to conclude that TEMRA CD8+ T cells play an active role in humoral rejection. These findings have therapeutic implications and can help to reduce rejection rates in kidney transplant recipients.
Using Single-Cell Analysis to Identify Drivers of Immune Response
Characterizing the function of individual immune cells in transplantations can help to improve clinical outcomes, reduce the rate of rejection, and improve post-transplantation treatment. By using single-cell functional analysis to identify key functional metrics, including polyfunctionality and PSI, researchers can gain a better understanding of how individual immune cells work to orchestrate an immune response. This study demonstrated how polyfunctionality can be used as a potential noninvasive assessment of peripheral T cell function, significantly segregating kidney transplant recipients who did and did not experience rejection. IsoPlexis’ single-cell functional phenotyping gives researchers a powerful tool to investigate individual immune cell function and reveal key functional drivers, providing unique, actionable insights to drive novel discoveries and the development of improved therapies.