Lipids are required for the development of B razil nut allergy: the role of mouse and human i NKT cells

Background Lipids are required for mice sensitization to B er e 1, B razil nut major allergen. Here, we characterized different lipid fractions extracted from B razil nuts and the lipid‐binding ability of B er e 1. Further, we determined their in vivo ability to induce B er‐specific anaphylactic antibodies and the role of invariant natural killer T (i NKT ) cells in this process. Methods Wild‐type ( WT ) and i NKT cell‐deficient mice were sensitized with B er e 1 and specific lipid fractions, and anaphylactic antibodies were measured by enzyme‐linked immunosorbent assay ( ELISA ) and passive cutaneous anaphylaxis ( PCA ). The lipid‐binding characteristic of B er e 1 ( B er) was established by using fluorescent probes and 15 N ‐labeled NMR . In vitro production of IL ‐4 was determined in B er/lipid C ‐stimulated mouse i NKT cells and human T ‐cell lines containing NKT s primed with CD 1d+ C 1 R transfectants by flow cytometry and ELISA , respectively. Results Only one specific lipid fraction (lipid C ), containing neutral and common phospholipids, induced B er anaphylactic antibodies in mice. B er e 1 has a lipid‐binding site, and our results indicated an interaction between B er e 1 and lipid C . i NKT ‐deficient mice produced lower levels of anaphylactic antibodies than WT mice. In vitro , B er/lipid C ‐stimulated murine i NKT cells produced IL ‐4 but not IFN ‐gamma. Human T ‐cell lines derived from nut‐allergic patients produced IL ‐4 to B er/lipid C in a CD 1d− and dose‐dependent manner. Conclusion Lipid fraction C from B razil nut presents an essential adjuvant activity to B er e 1 sensitization, and i NKT cells play a critical role in the development of B razil nut‐allergic response.