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The Role Of Nkt Organs In NKT Cells

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NKT TCRs are traditionally categorized into two distinct populations based on the TCR gene usage and antigen specificity, namely the invariant/type I NKT TCRs and diverse/type II NKT TCRs (Godfrey et al., 2004b). For the past two decades, much of the work in the field of NKT biology focused on the type I NKT cells largely due to their ability to recognize α-GalCer loaded CD1d tetramers (Benlagha et al., 2000). While CD1d-α-GalCer tetramers still remain as a major tool to characterize NKT cells, type II NKT cells do not recognize α-GalCer and as a result, their role in cellular immunity remain largely unknown. Interestingly, type I and type II NKT TCRs function as two discrete populations where not only do these cells recognize a different…show more content…
Notwithstanding the concern, Jα18−/−mice has practically still remained as a primary tool for understanding the functional relevance of type II NKT cells.
Recent work by Tatituri et al. (2013) have identified several type II NKT cell reactive phospholipids from the cell wall of Mycobacterium tuberculosis and Corynebacterium glutamicum, thereby provided a direct evidence for the role of type II NKT cells in microbial infections. These lipids were identified as phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylinositol and exhibited reactivity for a range of type II NKT cell hybridomas (Tatituri et al., 2013). Similarly, Wolf et al. (2015) have described the reactivity of type II NKT cell hybridomas for phosphatidylglycerol derived from the cell wall of Listeria monocytogenes (Wolf et al., 2015). While these studies clearly underlined the immunogenicity of type II NKT cells for microbial antigens, the selectivity and specificity of these lipids remained doubtful largely due to their abundance in mammalian counterpart (Cox et al., 2009; Gumperz et al., 2000).
NKT cells also exhibit reactivity for a range of α- and β-linked glycolipids when presented by CD1d (Godfrey et al., 2010; Venkataswamy and Porcelli, 2010). The α-glycosidic linkage that defines α-GalCer and several
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