MARK2 and systemic lupus erythematosus: The serine/threonine kinase MAP4K3 (also named GLK) directly interacts with and phosphorylates PKCθ in T cells, resulting in T-cell activation.13 GLK overexpression in murine T cells induces IL-17A production and T-cell hyperactivation, leading to autoimmune inflammatory diseases.14 Moreover, GLK is overexpressed in T cells in patients with autoimmune diseases including SLE13 15–18; GLK-overexpressing T-cell population is correlated with the disease severity of patients with SLE.13 17 To date, the mechanism of GLK overexpression in patients with SLE remains unclear.