| Popis: |
Invariant natural killer T cells (iNKT), a subclass of white blood cells, are responsible for the production of non-specific cytokines which induce a systemic uncontrolled immune response. They are distinctive in having a specific T-cell receptor that recognizes glycolipid antigens. The natural antigen was not identified until quite recently, when targets were isolated from S. pneumoniae. A bioactive fraction was identified from the extract: a disaccharide moiety attached to diacylglycerol (DAG). The glycolipid antigen reportedly activated iNKT cells. However, these tests were carried out using very small amounts of isolated glycolipids, and as a result it is impossible to determine whether the activity was due to this compound or to some minor impurity. There was also insufficient evidence to conclusively confirm the proposed structure of the glycolipid. Consequently, we recently synthesized the glycolipid to both confirm the structural assignment and to provide a useful chemical probe for immunologists. This presentation will discuss this S. pneumoniae glycolipid, its total synthesis, and our surprising re-evaluation of their immunological activity. |
