TAP-independent, β2-microglobulin-dependent surface expression of functional mouse CD1.1

Abstract

CD1 molecules consist of β2-microglobulin (β2m) noncovalently complexed to a non-major histocompatibility complex (MHC)-encoded monomorphic integral protein homologous to MHC class I α chains. Little is known about the requirements for cell surface expression and T cell recognition of CD1. We inserted the mouse CD1.1 gene into vaccinia virus to create a recombinant virus expressing CD1.1 under the control of a viral promoter. Using this recombinant virus to infect normal or mutant cell lines, we found that the expression of molecules reactive with the CD1.1-specific monoclonal antibody 3C11 requires the expression of β2m but was not affected by the absence of the MHC-encoded peptide transporter (TAP). Consistent with these results, IL- 2 production by the mCDL1-specific T cell hybridoma DN32.D3 was induced by thymocytes from normal mice or mice with a homozygous deletion of the TAP1 gene, but not by thymocytes from mice with a homozygous deletion of the β2m gene. These results indicate that expression of functional mCD1.1 occurs in a β2m-dependent, TAP-independent manner.