Biochemical analysis of a novel H-2 class I-like glycoprotein expressed in five AKR-(Gross virus) derived spontaneous T cell leukemias.

The H-2 class I Ag profiles of five spontaneous AKR (H-2K) Gross virus leukemic cell lines were analyzed. A novel H-2 class I, "alloantigen"-like glycoprotein was immunoprecipitated and isolated from all the tumor cell lines using an H-2Dd-specific mAb 35-5-8. The novel Ag was also recognized in vitro by anti-H-2Dd-specific CTL. In addition, DNA from all the thymomas, but not the DNA from normal adult AKR thymic cells showed a transcribed gene detectable with an H-2Dd-specific oligonucleotide probe. The molecular profile of the novel antigen was further studied by two-dimensional gel electrophoresis and analyzed by a computer based image analyzer system and reverse-phase HPLC tryptic peptide mapping. Its molecular pattern was different from the syngeneic H-2Kk, H-2Dk, and the allogeneic H-2Dd gene products. The two-dimensional gel pattern of the novel H-2 class I molecule had a different overall structure reflected in isoelectric point, number, and distribution of polypeptide spots. The tryptic peptide map analysis showed six peaks exclusively identified with the novel Ag. The calculated degree of homology with the corresponding H-2Dd, H-Dk, and H-Kk peptides was 41, 56, and 51%, respectively. In addition, an unusual cell surface distribution of the novel Ag was observed in most of the leukemic lines. The removal of sialic acid residues by neuraminidase treatment facilitated the detection of the allodeterminants by anti-H-2Dd-specific mAb and CTL. Furthermore, we showed that in one AKR tumor line, 424, there is a close association of the novel Ag with the syngeneic class I molecules. Prior preclearance of the syngeneic class I molecules revealed the presence of the H-2Dd-like allospecificity. The genetic and molecular relationship between the expression of this novel class I-like glycoprotein and the recently sequenced Q5 gene is under current investigation.