Changes of H-2 antigen expression on thymocytes during leukemia development by radiation leukemia virus

The expression of antigens encoded by the K and D region genes of the major histocompatibility complex on thymocytes of BL/6 mice infected with Radiation Leukemia Virus (RadLV) variants, A-RadLV to which they are sensitive or D-RadLV to which they are resistant, was investigated. Reduced thymus cellularity due to the thymolytic effect of both RadLV variants (30-40% cell reduction within 24 h after intrathymic virus injection) was accompanied with elevated H-2 expression on thymocytes. A high density of H-2D and to a lesser degree increased expression of H-2K were observed following infection with both virus variants. This elevated H-2 expression was maintained transiently for 6-7 weeks in the resistant situation and persisted in the sensitive situation until overt leukemia developed. The occurrence of A-RadLV transformed cells in 75% of the tested thymuses within 10 days after infection (vs 16% in D-RadLV treated mice) and their further expansion until overt leukemia developed could explain the continued expression of elevated H-2 expression on thymocytes in the sensitive situation. The majority (85%) of the primary A-RadLV induced leukemias tested expressed more H-2D/H-2K gene products than normal thymocytes. We conclude that leukemia development due to RadLV infection is not associated with the reduction or disappearance of H-2D/H-2K gene products.