Localization of adult T-cell leukemia-associated antigens by the immunocolloidal gold method.

Adult T-cell leukemia-associated antigen (ATLA) and adult T-cell leukemia virus (ATLV) antigens were localized in the MT-2 cell system by the immunocolloidal gold method using 71 human sera having various anti-ATLA titers and rabbit anti-ATLV antisera. In the thin-section method with anti-ATLA-positive human sera and rabbit antisera, protein A-gold particles were preferentially observed on and around sectioned adult T-cell leukemia (ATL) virions located in pericellular aggregates and within the cytoplasmic vacuoles but nowhere else in a significant number. The number of gold particles per ATL virion was statistically well correlated with the anti-ATLA titers of human sera applied (p less than 0.005). The preembedding method showed that pericellular ATL virions were specifically tagged with protein A-gold, but the antigens in question were not expressed on the plasma membrane of MT-2 cells. The absence of ATLA and ATLV antigens on the plasma membrane constitutes a unique pathobiological feature of ATL and ATLV as compared with other retrovirus systems.