Kinya Nagata

Nature of Adult T-Cell Leukemia-Associated Membrane Antigen on the Surface of Adult T-Cell Leukemia Virus-Carrying Cells as Revealed by Membrane Immunofluorescence

Adult T‐cell leukemia‐associated membrane antigen (ATLMA) expressed on the surface of living ATL virus (ATLV)‐carrying cells was investigated by an indirect membrane immunofluorescence method using natural antibodies to ATLV in human sera. All the ATLV‐positive cell lines tested that had cytoplasmic ATL‐associated antigen (ATLA) detectable in acetone‐fixed cell smears were also positive for ATLMA, but ATLMA was not detected in any ATLV‐negative cell lines. The frequencies of ATLA‐ and ATLMA‐bearing cells in seven cell lines tested were roughly parallel. The frequency of expression of both ATLMA and ATLA in cultures of MT‐1 cells increased in the presence of 5‐iodo‐2′‐deoxyuridine. All human sera having ATLA antibody had ATLMA antibody and the titers of the two were similar in most of the sera. The anti‐ATLMA titers of human sera determined by using an ATLV‐bound non‐ATL T‐cell line as antigen were also similar to the anti‐ATLA titers. Absorption of anti‐ATLMA‐positive sera with living MT‐2 cells, in which almost 100% of the cells express ATLA and ATLMA, caused parallel decreases in the anti‐ATLA and anti‐ATLMA titers. Analysis of the 125I‐labeled surface of MT‐2 cells by immunoprecipitation with anti‐ATLMA‐positive human serum followed by gel electrophoresis revealed that p19, p24, p28, and p46 polypeptides were specifically precipitated. These data suggest that ATLMA on the cell surface is not distinguishable from ATLA in the cytoplasm.