SPONTANEOUS PRODUCTION OF INTERLEUKIN-10 BY B-LYMPHOCYTES AND MONOCYTES IN SYSTEMIC LUPUS-ERYTHEMATOSUS

Interleukin-10 (IL-10) production by B lymphocytes has previously been demonstrated for malignant cells and for in vitro activated normal B cells. Spontaneous in vivo production of IL-10 by normal B lymphocytes has only been demonstrated in mice, in which autoreactive Ly1+ B cell s are involved. In the present study, spontaneous expression of the IL -10 gene by peripheral blood mononuclear cells was investigated in sys temic lupus erythematosus (SLE), a human disease involving autoreactiv e B cells. Of the 47 SLE patients tested by coupled reverse transcript ase-polymerase chain reaction, 34 scored positive, contrasting with on ly 1 positive out of 34 normal subjects (p < 0.001). Spontaneous in vi tro production of IL-10 by PBMC, determined using an ELISA assay, was 33 times higher in SLE than in controls (2623 +/- 728 pg/ml vs 79.3 +/ - 34.5 pg/ml, respectively) (p < 0.001). The level of production of IL -10 in SLE was unrelated to either clinical or biological markers of d isease activity. Among PBMC, monocytes and B lymphocytes both contribu ted to IL-10 production, whereas T cells did not. IL-10 overproduction in SLE suggests that this Th2-type interleukin plays a role in the pr oduction of autoantibodies through pathways involving both paracrine p roduction by monocytes and autocrine IL-10 production by autoreactive B cells.