Membrane expression of caveolin-1 in HTLV-1–infected T-cell lines and primary ATL cells and detection of caveolin-1 in plasma. (A) Flow cytometric analysis of T-cell lines and PBMCs derived from a healthy donor and patients with ATL. Cells were stained for caveolin-1 with phycoerythrin-conjugated monoclonal anti–caveolin-1 antibody. (B) Detection of intracellular Tax protein expression in HTLV-1–transformed T-cell lines. The Tax protein was detected with the Lt-4 monoclonal antibody. (C) Detection of caveolin-1 in plasma. Plasma samples from healthy donors (n = 2) and patients with acute-type ATL (n = 9) were screened by Western blot (left). Plasma was serially diluted (1:2, 1:40, 1:100, 1:200, 1:400, and 1:1000) and loaded (right). Phosphorylated caveolin-1 in plasma was also determined by Western blot with the use of a phosphospecific monoclonal antibody that selectively recognizes only Tyr-14 phosphorylated caveolin-1. Representative results of 3 separate experiments with similar findings.