Localization of iNKT subsets determines lipid response (APP2P.101)

Abstract

Abstract iNKT cells can be rapidly activated by α-galactosylceramide (α-GalCer), and α-GalCer or analogues of it are being tested for clinical use against certain cancers and autoimmune diseases. Recent studies in our lab showed that iNKT cells are comprised of NKT1, NKT2 and NKT17 effector subsets. In the current study, we asked whether these different iNKT subsets respond equivalently to α-GalCer using Nur77GFP transgenic mice to quantify the antigen specific response. We observed a robust response by NKT1, but not NKT2, in the spleen, despite in vitro stimulation showing they could be equivalently activated. Using an in vivo antibody-labeling technique, we found that NKT1 possess significantly higher accessibility to blood than NKT2, suggesting that NKT1 cells are preferentially localized to red pulp. This was confirmed by tetramer-based immunofluorescence studies. As expected, i.v. labeled iNKT cells showed a greater response than unlabeled cells. Thus, iNKT cells with accessibility to blood are the predominant cells to respond to lipid. Consistent with this, we observed a robust response of liver iNKT cells, and no response by lymph node iNKT cells, regardless of the subset. Because iNKT subsets produce distinct cytokines, their differential response to i.v. lipids is a critical consideration in therapeutic applications.