Effects of Cryopreservation on Immune Responses: VIII. Enhanced Secretion of Interferon-γ by Frozen Human Peripheral Blood Mononuclear Cells

Abstract

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.