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Stimulation of leukaemic cells from adult T‐cell leukaemia patients with bacterial superantigens

Bacterial superantigens stimulate T cells in a manner that is restricted to the Vβ of the T‐cell receptor. We examined the ability of adult T‐cell leukaemia (ATL) cells to respond to these superantigens. Mononuclear cells from 10 patients were cultured with staphylococcal enterotoxin A (SEA), staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin‐1 (TSST‐1), and their response was determined by MTT assay and 3H‐thymidine incorporation assay. Cells from six patients showed a specific response to a single superantigen. In two cases the cells responded to TSST‐1 and bore Vβ2, the known target of TSST‐1. In three cases the cells responded to SEA with one bearing Vβ9, a target of SEA, and one bearing Vβ16. In one case the cells responded to SEB. Most of the cells which proliferated in response to superantigens were determined genetically to be leukaemic. The response to TSST‐1 was inhibited by anti‐Vβ2 antibody. The responding cells showed a strongly enhancement expression of interleukin‐2 receptor. These findings indicate that leukaemic cells from a proportion of ATL patients have an ability to respond to T‐cell receptor‐dependent superantigens. This suggests that bacterial infection in such patients may contribute to the expansion of ATL cells.