Established from the pericardial fluid of a 15-year-old man with acute lymphoblastic leukemia (ALL) at relapse (with accompanying thymoma) in 1983; cells were described as: (i) showing NK activity and ADCC (antigen-dependent cell-mediated cytotoxicity), (ii) having their T cell receptor (TCR) genes in germline configuration, and (iii) expressing no TCR proteins (also CD3-, CD16-, CD56+, CD57-)