FAS and systemic lupus erythematosus: T cells in these mice accumulate in large numbers in lymphoid organs through dysregulated homeostatic proliferation that is enhanced in the absence of the death receptor, Fas (CD95).17 The dysregulation of T cells includes the emergence with age of an increasingly large proportion of polyclonal CD4–CD8– TCR-αβ+ cells that derive from CD8+ precursors during homeostatic proliferation.17 A CD4–CD8– TCR-αβ+ subset also occurs in human SLE.3 4 Similar to human SLE T cells, the lpr CD4–CD8– TCR-αβ+ subset also manifested enlarged mitochondria and spontaneous MAVS oligomerisation.