Table 1. Two-hit model of autoimmunity: lymphopenia and loss of homeostatic control.

		Lymphopenia (neonatal/genetic/experimental)	Loss of homeostatic control (unresponsiveness of T cells to TGF-β in Zhang and Bevan's study)	Onset of autoimmunity
Neonatal, TGF-βRII KO	CD4-Cre, early-staged	+	+	Yes
	dLck-Cre, late-staged	+	−	No
	grow into adult	−	+	No
Adult, Rag1−/−	+ control T cells	+	−	No
	+ TGF-βRII-deficient T cells (dLck-Cre)	+	+	Yes
Adult, irradiated	+ control T cells	+	−	No
	+ TGF-βRII-deficient T cells (dLck-Cre)	+	+	Yes

Abbreviations: dLck, distal Lck promoter; KO, knockout; TGF-β, transforming growth factor-β.