FIG. 2.

Schematic diagram of CD1d-based aAPCs. aAPCs can be made by coupling CD1d-Ig and various costimulatory Abs to magnetic beads. These noncellular aAPCs can then be loaded with lipid antigen of choice. In this system, CD1d-Ig is used to provide the cognate antigen-specific signal through the TCR and anti-CD28, CD44, CD161 Abs will provide the costimulatory signal. The B7–CD28 interaction was one of the first costimulatory pairs defined at a molecular level. As such, this has served as a cornerstone for studies involving costimulation. However, these molecules may not be the major sources of costimulation for NKT cells. In fact, a variety of additional costimulatory complexes have been defined over the past few years, including CD161 and CD44, which will offer interesting alternatives to the B7–CD28 interaction. aAPCs, artificial antigen presenting cells; TCR, T cell receptors.