Invariant natural killer T cells, originally characterized in mice and more recently defined in humans, are a unique, conserved T-cell sublineage possessing a rearrangement of the T-cell antigen receptor (Vα14Jα18 in mice and Vα24Jα18 in humans). Human natural killer T cells also have an invariant β chain (Vβ11). Vα24Vβ11 binds to glycolipids presented by CD1d, a major-histocompatibility complex class I–like molecule expressed on dendritic cells, monocytes, and subgroups of B cells.1 The glycolipid antigens are also highly conserved and include the synthetic glycolipid α-galactosylceramide, self glycolipids, and glycolipids from bacteria and plant pollens. The hallmark response of invariant natural killer . . .