Intriguingly, several studies have suggested that GML suppresses inflammatory processes, indicating that
GML may also have an immunomodulatory role. GML treated T cells have decreased cellular proliferation when
stimulated with phorbol 12-myristate 12-acetate (PMA), concanavalin A (ConA), and Toxic Shock Syndrome
Toxin-1 (TSST-1)13. Additionally, GML treatment decreases inositol triphosphate (IP3) generation upon TSST-1
stimulation, indicating decreased phospholipase Cγ 1 (PLC-γ 1) enzymatic activity14. These studies suggest that
GML potentially alters T cell activation. However, how GML treatment affects the full T cell activation response
from signaling events to effector functions is not well understood. In addition, the mechanism behind how GML
mediates suppressed T cell activation is completely unknown.
To directly address these questions, we mechanistically characterized how GML affects human primary T
cell activation. We observed that GML treatment drastically altered the balance of ordered vs. disordered lipid
phases in the membrane. As a consequence, TCR-induced LAT, PLC-γ , and AKT microcluster formation from
aggregation of smaller nanocluster units, PI3K-AKT signaling axis, and calcium influx were potently inhibited
by GML treatment. Overall these defects resulted in decreased TCR induced cytokine production. This is the
first mechanistic evidence showing that GML suppresses the human immune system. These findings further
the current understanding of this compound but also open up the possibility that GML could serve as a potent
immunosuppressant.