Cell-mediated immune responses between HLA-identical siblings: recognition of antigenic changes associated with acute myelogenous leukaemia.

Cell-mediated immune reactions between a patient suffering from acute myelogenous leukaemia (AML) and an HLA-identical sibling were studied in order to characterize the in vitro reactions in MLC and CML prior to bone marrow transplantation. Our results indicated that antigenic differences were detectable between the blasts and the remission lymphocytes. While the normal sibling did not respond in MLC to her HLA-identical sister's remission lymphocytes, there was an anti-blast response. This proliferative response, however, did not lead to the development of detectable cytotoxic cells capable of destroying blast cells. Unrelated individuals, on the other hand, responded strongly both in MLC and CML to the allogeneic tumour blasts and remission lymphocytes of the patient and the lymphocytes of the healthy sibling. The kinetics and magnitude of the MLC response to blast cells was different from that to remission lymphocytes. This response indicated that the blast cells expressed antigenic differences which were recognized in MLC by both the HLA-identical sibling and unrelated individuals. Furthermore, these tumour cells were capable of sensitizing allogeneic, but not syngeneic lymphocytes to become cytotoxic, though they seemed to be more resistant to destruction in CML than normal cells.