An overview of our research
T cells are essential mediators of human immunity which can detect and eliminate pathogens and malignant cells. Despite the capacity of T cells to mount potent anti-tumor responses, in many cases they fail to do so. Given the need to improve existing immunotherapies and develop new treatments, it is critical that we understand T cell behavior.
The Courtney lab seeks to understand how T cells make decisions that affect their behavior and to leverage these insights for the development of new immunotherapy strategies. We take an interdisciplinary approach by applying immunology, chemical biology, and genetics to study and manipulate T cell signaling pathways. We believe that by understanding and manipulating how T cells make decisions we can improve their capacity to target and eliminate cancer.
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
By using chemical tools to manipulate the pool of active Lck, we can affect how T cells sense low affinity (weak) antigen. 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
To evaluate changes in how T cells sense and respond to antigen we employ an expanding toolbox of approaches to assess T cell function. 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 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.