Burkitt's lymphoma has proved to be a very useful model for the evaluation of both massive therapy regimens and purging techniques. Results from several centres now confirm a number of general principles in relation to the use of ABMT procedures in this tumour. Patients in whom conventional chemotherapy has failed can be cured by massive therapy but this should be limited to those who have responded to salvage regimens or have only achieved first PR. Chemoresistant relapse is unlikely to be cured and the high probability of a transient response does not justify the procedure in such cases. Important ongoing clinical studies include the use of ABMT in first CR for CNS disease or B-cell ALL. Results in allogeneic grafts suggest that current massive therapy regimens are curative in only 20–50% of patients (Appelbaum and Thomas, 1983) and new combinations are, therefore, still required. Phase I and II studies in patients with ‘resistant relapse’ are investigating the use of sequential high-dose alkylating agents and role of TBI.
The effect of freezing on phytohemagglutinin-induced interferon-γ (IFN-γ) production by human peripheral blood mononuclear cells (PBMCs) was studied. The possible mechanism responsible for the observed effects were also analyzed. Fronzen PBMCs produced significantly larger quantities (if IFN-γ than fresh cells. Like the frozen cells, the monocyte- and natural killer cell-eliminated populations of fresh PBMCs also secreted significantly larger quantities of IFN-γ. In contrast, the freezing process had no enhancing effect on IFN-γ production by monocyte-depleted PBMCs. Irradiated PBMCs also secreted larger quantities of IFN-γ. The results suggest that functional inactivation, of a subset of cryosensitive suppressor monocytes is associated with an increase in IFN-γ production by the T lymphocytes. The results provide further evidence that monocytes mediate their suppressive effect through the activation of a subset of radiosensitive, immuno-down-regulatory T cells. The ability of frozen cells to produce larger quantities of IFN-γ should be of clinical importance. For instance, cancer patients receiving frozen PBMCs as stem cell support (after myeloablative radio/chemotherapy) should benefit from the increased IFN-γ secretion because of its potent immunoregulatory, microbicidal, and antitumor activities.
