Methodology for in vitro Assessment of Human T Cell Activation and Blockade

Methods to test both the functionality and mechanism of action for human recombinant proteins and antibodies in vitro have been limited by multiple factors. To test the functionality of a recombinant protein or antibody, the receptor, the receptor-associated ligand, or both must be expressed by the cells present within the in vitro culture. While the use of transfected cell lines can circumvent this gap, the use of transfected cell lines does not allow for studying the native signaling pathway(s) modulated by the specific recombinant protein or antibody in primary cells. The present protocol utilizes sort purified CD14⁺ monocytes and T cells, both CD4⁺ T cells and CD8⁺ T cells, from healthy donors in a co-culture system. This methodology is particularly relevant for testing recombinant proteins or antibodies that are putative therapeutics for the treatment of autoimmune disease and cancer. While the current protocol focuses on co-cultures containing B7-H4 expressing monocytes plus either autologous CD4⁺ T cells or CD8⁺ T cells, the protocol can be modified for the user's specific needs.

Divergent SATB1 expression across human life span and tissue compartments

Special AT-rich binding protein-1 (SATB1) is a global chromatin organizer capable of activating or repressing gene transcription in mice and humans. The role of SATB1 is pivotal for T-cell development, with SATB1-knockout mice being neonatally lethal, although the exact mechanism is unknown. Moreover, SATB1 is dysregulated in T-cell lymphoma and proposed to suppress transcription of the Pdcd1 gene, encoding the immune checkpoint programmed cell death protein 1 (PD-1). Thus, SATB1 expression in T-cell subsets across different tissue compartments in humans is of potential importance for targeting PD-1. Here, we comprehensively analyzed SATB1 expression across different human tissues and immune compartments by flow cytometry and correlated this with PD-1 expression. We investigated SATB1 protein levels in pediatric and adult donors and assessed expression dynamics of this chromatin organizer across different immune cell subsets in human organs, as well as in antigen-specific T cells directed against acute and chronic viral infections. Our data demonstrate that SATB1 expression in humans is the highest in T-cell progenitors in the thymus, and then becomes downregulated in mature T cells in the periphery. Importantly, SATB1 expression in peripheral mature T cells is not static and follows fine-tuned expression dynamics, which appear to be tissue- and antigen-dependent. Furthermore, SATB1 expression negatively correlates with PD-1 expression in virus-specific CD8⁺ T cells. Our study has implications for understanding the role of SATB1 in human health and disease and suggests an approach for modulating PD-1 in T cells, highly relevant to human malignancies or chronic viral infections.

Dissecting alterations in human CD8+ T cells with aging by high-dimensional single cell mass cytometry

We investigated the effect of aging on the multi-dimensional characteristics and heterogeneity of human peripheral CD8⁺ T cells defined by the expression of a set of molecules at the single cell level using the recently developed mass cytometry or Cytometry by Time-Of-Flight (CyTOF) and computational algorithms. CD8⁺ T cells of young and older adults had differential expression of molecules, especially those related to cell activation and migration, permitting the clustering of young and older adults through an unbiased approach. The changes in the expression of individual molecules were collectively reflected in the altered high-dimensional profiles of CD8⁺ T cells in older adults as visualized by the dimensionality reduction analysis tools principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE). A combination of PhenoGraph clustering and t-SNE analysis revealed heterogeneous subsets of CD8⁺ T cells that altered with aging. Furthermore, intermolecular quantitative relationships in CD8⁺ T cells appeared to change with age as determined by the computational algorithm conditional-Density Resampled Estimate of Mutual Information (DREMI). The results of our study showed that heterogeneity, multidimensional characteristics, and intermolecular quantitative relationships in human CD8⁺ T cells altered with age, distinctively clustering young and older adults through an unbiased approach.