Right on target: novel approaches for the direct visualization of CD1-specific T cell responses.

Abstract

T cells typically recognize peptide fragments derived from antigenic proteins when these fragments are bound to a groove in the major histocompatibility complex (MHC)-encoded class I and II molecules. This phenomenon is known as antigen presentation (1). CD1 proteins constitute a third family of antigen-presenting molecules with a specialized function: the presentation of (glyco)lipid antigens (2). Although several reports have described T lymphocytes that are reactive to such CD1-bound (glyco)lipids, overall there is only a limited knowledge of their biology. Two papers in this issue of PNAS now describe an elegant method that allows the efficient refolding of recombinant CD1 proteins (3, 4). Moreover, they show that this method is useful for the construction of tetramers, reagents that can be used to identify and purify CD1-reactive cells with particular specificities. Reagents of this type should enhance our understanding of the function of CD1-reactive T lymphocytes greatly.