INCREASED BASAL PRODUCTION OF INTERLEUKIN-10 BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN HUMAN ALVEOLAR ECHINOCOCCOSIS

The secretion of IL-10 by peripheral blood mononuclear cells (PBMC) an d the expression of IL-10 mRNA in fractionated CD4(+) and CD8(+) lymph ocyte subsets and non-B-non-T cells, with and without stimulation by t he mitogen phytohemagglutinin-C (PHA-C) and specific Echinococcus mult ilocularis is (E. multilocularis) antigens, were assessed in 7 patient s with alveolar echinococcosis (AE) and 6 healthy subjects. Results of studies on IL-10 were compared to those on IFN-gamma, IL-4 and IL-5 i n the same patients and control subjects. IL-10 production was signifi cantly higher in patient PBMC-culture supernatants than in the control group supernatants, both at the basal level and after mitogen or spec ific E. multilocularis antigen stimulation, Both CD4(+) and CD8(+) lym phocyte populations and non-B-non-T cells of AE patients and controls expressed IL-10 mRNA. Semi-quantification of IL-10 mRNA revealed a sig nificantly higher transcript level in unstimulated-CD8(+) T cells from AE patients in comparison with CD8(+) T cells of healthy donors. PBMC from patients produced very low levels of IL-4 but the production of IFN-gamma was not significantly depressed compared to the controls. PB MC, isolated from 4 AE patients and 4 control subjects stimulated with specific E. multilocularis antigens, secreted IL-5; IL-5 mRNA was onl y detected in the CD4(+) lymphocyte subset, The secretion of IL-5 and the expression of IL-5 mRNA in healthy subjects could be due to the pr esence of nonspecific mitogenic parasitic factors. This non-specific m itogenic activity of the parasite, besides inducing a high secretion o f IL-10 in patients with evolutive AE, may contribute to the lack of h ost control of parasite growth and to the persistence of granulomatous lesions, due to the inhibition of an efficient Th1 immune response.