Origin and function of adherent lymphokine activated killer cells in patients with chronic myeloid leukaemia who relapse following bone marrow transplantation.

Adherent lymphokine activated killer (ALAK) cells are a subpopulation of activated natural killer (NK) cells with MHC unrestricted antitumour activity distinguished by their propensity to adhere to plastic in the presence of interleukin-2 (IL-2). We generated ALAK cells from seven patients with chronic myeloid leukaemia (CML) following Campath-1-depleted bone marrow transplantation (BMT). Five had relapsed and were in chronic phase, one had cytogenetic evidence of relapse and one had prior evidence of cytogenetic relapse but was in complete remission at time of study. Phenotypically the ALAK cells included both CD56+/CD3- NK cells and CD56-/CD3+ T cells. The CD3- subpopulation were studied cytogenetically and their functional activity tested in a 4 h 51Cr release cytotoxicity assay using the pretransplant leukaemia cells as targets. Cytogenetic studies showed that the ALAK cells from six patients were Ph negative, and where donor and recipient were sex mismatched, ALAK cells were exclusively of donor origin. In one patient ALAK cells were Ph positive and of recipient origin in eight of nine metaphases. In the 51Cr release assay the ALAK cells showed significant lysis of the pretransplant leukaemia in five of the seven patients tested. These data indicate that in CML patients who relapse post-BMT the NK cells are usually of donor origin but may be recipient-derived. In most patients these ALAK cells have antileukaemic activity in vitro.