An overview of our research
T cells can distinguish between diseased and non-diseased states. T cells are an essential component of the human immune system that can protect us from pathogens and cancer. The Courtney lab seeks to understand how T cells make decisions that affect their behavior. We take an interdisciplinary approach by applying immunology, chemical biology, and genetics to study and manipulate T cell signaling pathways. These signaling pathways convey information that allows a T cell to sense and response to changes in its environment. An understanding how signaling pathways in T cells coordinate cellular behaviors is needed to realize the full potential of T cells as therapeutic entities for the treatment of human disease.
Manipulating T cell signaling
When antigen is bound by the T cell antigen receptor (TCR), this recognition event is converted into an intracellular signal by the Src family kinase Lck. Because Lck phosphorylates the TCR complex, its activity is critical for T cell activation. The phosphatase CD45 activates Lck by opposing the negative regulatory kinase Csk. Inhibition of Csk causes the activation of Lck in resting T cells. We have found that inhibition of Csk can augment TCR signaling by increasing the amount of active Lck (Manz et al., eLife 2015; Courtney et al., Science Signaling 2019).
Regulating how T cells sense and respond to antigen
We can affect how T cells sense low affinity (weak) antigen using chemical tools to manipulate the pool of active Lck. Increasing the amount of active Lck shifts the threshold for activation and allows T cells to respond to weaker antigen. Treatment with a Csk inhibitor increases the amount of active Lck and potentiates the capacity of OT-1 T cells to respond to a weak peptide antigen (G4). In contrast, OT-1 T cells do not become activated when treated with an intermediate dose of PP2 (Courtney et al., 2019).
Functional readout of antigen recognition: Cell-mediated cytotoxicity
T cells can attack and destroy cancerous cells, but cancer can disable or evade this attack. Given the need to improve existing immunotherapies and develop new treatments, it is critical that we understand T cell behavior and to leverage these insights for the development of new immunotherapy strategies. To assess the relationship between T cell signaling and cancer cell recognition, we employ an expanding toolbox. Illustrated here is an example of cytotoxic T lymphocytes (CTLs) recognizing and killing MC38 adenocarcinoma cells bearing antigen. CTLs and MC38 cells are combined in individual wells of a 96-well plate. Imaging cytometry was used to quantify T cell activation (GFP reporter) in combination with cell death (PI staining). The scatter plot is generated by evaluating each individual cell in a well. The recognition of a presented tumor antigen can be observed to cause robust T cell activation and killing of MC38 cancer cells compared to a control lacking antigen.
