Suppression of IL-2 production by cryopreserved peripheral blood mononuclear cells from patients with active visceral leishmaniasis in Sicily.

The ability of PBMC from eight patients with confirmed visceral leishmaniasis (Leishmania donovani) to produce IL-2 in response to PHA in vitro was investigated. PBMC from the patients produced significantly lower levels of IL-2 and had reduced proliferative response to PHA at the time of disease diagnosis compared with healthy controls. Their ability to produce IL-1 in response to LPS was, however, unaltered. The patients also showed normal levels of OKT4+ and IL-2R+ cells in the peripheral blood, as judged by specific immunofluorescence staining. All patients were given antimony therapy, and five were cured. The recovered patients showed significant improvement in the IL-2 producing capacity of their PBMC. The PBMC preparations of patients and controls were cryopreserved before and after successful chemotherapy on the patients. The frozen cell preparations were thawed and viable autologous cells cocultured with equal numbers of PBMC from patients before and after chemotherapy. The frozen cells from five healthy controls showed little or no difference whether they were cultured together or separately. In contrast, coculturing of cells from the five recovered patients with autologous pretreatment cells produced significantly and consistently lower levels of IL-2 compared with those produced when the cells were cultured separately. These results therefore demonstrate that the PBMC from patients with visceral leishmaniasis contain a population of cells that are capable of suppressing the IL-2 production by autologous PBMC from recovered patients. The method of cryopreservation should be useful for studying the immune regulation in this and other clinical diseases in vitro.