CD4 and autoimmune disease: Halofuginone, an analog of the quinazolinone alkaloid febrifugine extracted from the plant Dichroa febrifuga, has been demonstrated to inhibit in vitro human T helper 17 cells (Th17), a distinct subset of CD4+ T cells involved in the pathogenesis of inflammatory and autoimmune diseases, by activating the amino acid starvation response (AAR) [73].