Alternative activation of macrophage by IL-10

Macrophage activation by proinflammatory stimuli is suppressed by IL-10. We tested the hypothesis that IL-10 induces an alternative state of macrophag e activation rather than solely mediating suppression. We therefore searche d for genes the expression of which might be up-rather than downregulated i n response to IL-10. Total RNA was obtained from mouse macrophages J774 A.1 before or after stimulation with IL-10 (20 ng/ml). Poly(A)+RNA was isolate d in both cases in order to obtain driver and tester mRNA. Subtraction supp ression hybridization was performed using the PCR-select cDNA subtraction p rocedure. After evaluation of the subtraction efficiency the subtracted cDN A library was cloned into pCRII.1. A total of 1,300 clones were obtained. S outhern blot hybridization analysis was performed as the fi rst screening s tep of th is total number of clones. 140 (10.7%) were identified as upregul ated in response to IL 10. Sequence ana lyses so far showed perfect or near per feet matches with already known genes for the majority of clones. Our results clearly indicate that IL-10 stimulates the expression of a large nu mber of genes in macrophages. We conclude that IL-10 induces in macrophages a noninflammatory state of reactivity which may serve to contain proinflam matory conditions. Copyright (C) 2000 S. Karger AG, Basel.