NKT are an <i>in vivo</i> source of IL-33.

<p>(A) IL-33 mRNA found in cell populations FACS sorted from the lung at 12 d.p.i.. (B) IL-33 protein in NKT as detected by intracellular staining (filled) compared to FMO control (shaded gray) at 12 d.p.i. (C) Total NKT cells identified in the influenza-infected lung as defined by CD3 and CD1d tetramer staining. (D) BAL IL-5 levels at 7 d.p.i. in indicated mouse strains. Data is representative of at least 2 independent experiments with 2–3 mice each. mRNA was collected from pooled, sorted cell populations from >5 mice. Bars = +/− SEM. *p<.05.