The synthesis and expression of HLA-A and -B antigens in Xenopus laevis oocytes

Purified mRNA's encoding the HLA-A and -B antigen heavy chains or beta 2-microglobulin were prepared from human B lymphoid cells by positive hybridization selection procedures. The role of chain association in the biosynthesis and intracellular transport of HLA-A and -B antigens was investigated by injecting these mRNA species into Xenopus laevis oocytes and following the fates of the translated products by immunoprecipitation. When mRNA encoding beta 2-microglobulin from the B lymphoblastoid cell line MST was coinjected with mRNA encoding the HLA-A and -B antigen heavy chains from the Burkitt lymphoma cell line Daudi, fully assembled class I antigens were detected using the monoclonal antibody W6/32. This result suggested that there may be no defect in the mRNA encoding Daudi HLA-A and -B antigen heavy chains. When the state of maturity of the N-linked glycan units on these class I antigen heavy chains was assessed, they were found to have undergone some processing. In contrast, when mRNA encoding immunoglobulin M (IgM) was injected into oocytes, the glycan units of the IgM heavy chains were found to be in the unprocessed (high mannose) form. This result shows that Xenopus oocytes can process some eukaryotic glycoproteins of exogenous origin.