Multiple defects in antigen presentation and T cell development by mice expressing cytoplasmic tail-truncated CDId

For members of the CD I family of beta(2)-microglobulin-associated lipid-presenting molecules, tyrosine-based motifs in the cytoplasmic tail and invariant chain (Ii) govern glycoprotein trafficking through endosomal compartments. Little is known about the intracellular pathways of CDI trafficking and antigen presentation. However, in vitro studies with cells transfected with mutant CDI that had a truncated cytoplasmic tail have suggested a role for these tyrosine motifs in some, but not all, antigenic systems. By introducing a deletion of the tyrosine motif into the germ line, and through homologous recombination in embryonic stem cells, we now describe knock-in mice with the CDId cytoplasmic tail deleted. Despite adequate surface CDId expression and the presence of Ii, these mutant mice showed multiple and selective abnormalities in intracellular trafficking, antigen presentation and T cell development, demonstrating the critical functions of the CDId cytoplasmic tail motif in vivo.