THE MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II-LINKED CIM LOCUS CONTROLS THE KINETICS OF INTRACELLULAR-TRANSPORT OF A CLASSICAL CLASS-I MOLECULE

The dominant trans-acting major histocompatibility complex (MHC)-linked class I modifier (cim) locus, previously recognized through its ability to determine altered alloantigenicity of a rat class I molecule, RT1.A(a), is shown here to influence class I intracellular transport. The MHC recombinant laboratory rat strains PVG.R1 and PVG.R8 display unusually long retention of RT1.A(a) within the endoplasmic reticulum or cis-Golgi. In appropriate F1 hybrid cells heterozygous for RT1.A(a) and another class I MHC allele, RT1.A(c), only the RT1.A(a) protein is subject to slow transport. The cim gene product therefore shows class I allele specificity in its action. cim appears to be a polymorphic locus whose product is directly involved in the processes of class I MHC assembly and/or intracellular transport.