Autocrine Deactivation of Macrophages in Transgenic Mice Constitutively Overexpressing IL-10 Under Control of the Human CD68 Promoter

Abstract

IL-10 plays an essential role in blocking cytokine production by activated macrophages. To analyze the consequences of enforced expression of IL-10 by macrophages on innate and adaptive immune responses, we generated transgenic mice (macIL-10tg mice) expressing an epitope-tagged IL-10 (Flag-IL-10) under control of the human CD68 promoter. Expression of Flag-IL-10 was constitutive and restricted to macrophages, as shown by sorting splenocyte cell populations and intracellular staining for IL-10. Transgenic macrophages displayed suppressed production of TNF-α and IL-12 upon stimulation with LPS. When macIL-10tg mice were challenged with LPS, serum levels of proinflammatory cytokines were attenuated compared with controls. Infection with Mycobacterium bovis bacille Calmette-Guérin resulted in ∼10-fold-higher bacterial loads than in wild-type mice. Normal T and B cell responses were observed in macIL-10tg mice, suggesting that macrophage-specific overexpression of IL-10 predominantly acts in an autocrine/paracrine manner, resulting in chronically deactivated macrophages that manifest an impaired ability to control pathogens.

Adult behavioral and pharmacological dysfunctions following disruption of the fetal brain balance between pro-inflammatory and IL-10-mediated anti-inflammatory signaling

“…MacIL-10tg animals have previously been shown to display a markedly attenuated pro-inflammatory cytokine response to immunological stimulation by the bacterial endotoxin LPS. 23 Consistent with previous results, 23 macIL-10tg animals displayed higher IL-10 levels in basal conditions compared to wt controls, as indicated by the 50-fold elevation of serum IL-10 in macIL-10tg relative to wt mice following the administration of vehicle (saline) solution ( Figure 1a). The serum IL-10 response to the PolyI:C-induced immune challenge was also greatly increased in macIL-10tg mice compared to wt controls at both sampling times (that is, at 1.5 and 5 h post-treatment; Figures 1b and c).…”

“…Consistent with the inhibitory effects of IL-10 on pro-inflammatory cytokine production, 22,23,37 macIL10tg animals displayed impaired peripheral IL-1b, IL-6 and TNF-a responses to the viral mimic PolyI:C in comparison with wt mice (Figure 1). This antiinflammatory effect is likely to be accounted for by the capacity of IL-10 to selectively suppress pro-inflammatory gene transcription in activated macrophages.…”

“…23 Transgene-bearing hemizygous male mice were mated with wt FVB females obtained from Jackson Laboratory (Bar Harbor, ME, USA). The resulting F1 hemizygous transgene-positive (macIL-10tg) female and male offspring were kept as transgene breeding pairs; and the resulting F1 transgene-negative control littermates (wt) were kept as wt breeders.…”

“…This genetic manipulation leads to the autocrine deactivation of macrophages, which is accompanied by attenuated pro-inflammatory cytokine reactions to acute immunological stimulation by the bacterial endotoxin lipopolysaccharide (LPS). 23 The restriction of IL-10 overexpression to macrophages allows us to specifically assess the impact of peripheral maternal IL-10 on the susceptibility to prenatal inflammationmediated behavioral and pharmacological dysfunctions in the grown offspring. This specificity is also in keeping with the hypothesis that maternal immunological factors transmitted to the offspring in utero may represent the critical link between prenatal infections and the emergence of brain and behavioral dysfunction later in life.…”

Vanin‐1 controls granuloma formation and macrophage polarization in Coxiella burnetii infection

“…This is consistent with reports on experimental visceral leishmaniasis in which neutralization of IL-10 enhances granuloma assembly and MU activation [27]. In mice over-expressing IL-10, the infection with Mycobacterium avium stimulates the formation of abnormal granulomas enriched with MU [28], whereas the over-expression of MU IL-10 has no effect on granuloma formation [29].…”