Translation in Xenopus laevis oocytes of hybrid selected LEW rat RT1.B alpha- and beta-chain transcripts results in serologically discrete class II polypeptide chain complexes.

Using the non-crossreactive mAb MRC-OX3 and MRC-OX6, two serologically distinct RT1.B-specific (I-A equivalent) alpha, beta heterodimers have previously been described by us as residing at the cell surface of LEW rat spleen cells. The two-chain elements were suggested to represent stable conformation isomers, diverged by dissociation of the mature gamma-chain from a mAb MRC-OX6 reactive biosynthetic intermediate, composed of terminally glycosylated alpha-, beta- and gamma-chains. In this study we addressed the question of whether or not the presence of terminally glycosylated invariant gamma-chain was obligatory for the formation of the two MRC-OX3 and MRC-OX6 reactive two-chain complexes. The synthesis of RT1.B-specific alpha, beta heterodimers was therefore initiated, in the absence of accompanying invariant gamma-chains, by microinjecting hybrid-selected RT1.B alpha- and beta-specific mRNA into oocytes of Xenopus laevis for translation. Class II molecules produced were analyzed by affinity chromatography of radioactive-labeled oocyte detergent lysates using the appropriate monoclonal immunoadsorbents for identification. Although rat gamma-chain mRNA was excluded in this assay system, distinct MRC-OX3 and MRC-OX6 reactive two-chain complexes were detected by two-dimensional gel electrophoresis. These findings clearly indicate that the formation of the two RT1.B-specific alpha, beta heterodimers is independent of the presence of the rat invariant gamma-chain.