Leukaemia of novel gastrointestinal T-lymphocyte population infected with HTLV-I.

In a 72-year-old man with watery diarrhoea and leukocytosis the proliferation of abnormal cells was studied in specimens obtained by endoscopic biopsy of the gastrointestinal tract. Flow cytometry of leukaemia cells revealed a monoclonal expansion of "double-negative" (CD4-, CD8-) cells bearing T-cell receptor (TCR) alpha beta products. Southern blotting confirmed monoclonal integration of HTLV-I. A novel T-cell subset of double-negative TCR alpha beta cells in the gastrointestinal tract in adult man may be a target for HTLV-I infection.