As Tbet and other factors implicated in immunopathology, such as GM-CFS, are not exclusively expressed by the Th17 cell lineage, we next assessed the susceptibility of Rag1ΔTbet mice in which Tbet was conditionally deleted via Rag1-Cre in all lymphocytes. The gene discussed is TBX21; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.