Efficient cell surface expression of class II MHC molecules in the absence of associated invariant chain.

摘要: The intracytoplasmic forms of class II (or Ia) major histocompatibility complex heterodimers are associated with a third glycoprotein, termed the invariant chain (Ii). This specific interaction has led to view that Ii plays necessary role in assembly, intracellular transport, and/or membrane insertion Ia molecules. To test this hypothesis directly, we have transfected complementary DNA clones encode murine alpha and beta chains into cells do not express any endogenous messenger RNA (mRNA) (COS-7 BALB/c 3T3 cells). After DNA-mediated gene transfer, significant cell surface expression was observed transient assays using COS-7 stable system cells. Furthermore, total levels mRNA were similar Ii- (transfected 3T3) Ii+ (B hybridoma) expressed nearly identical amounts Ia, suggesting efficiency equivalent two types and, therefore, independent Ii. These results indicate physiologic for is simply mediate molecules, alternative hypotheses concerning true function molecule need be considered.