Potential antiinflammatory effects of interleukin 4: suppression of human monocyte tumor necrosis factor alpha, interleukin 1, and prostaglandin E2.

TLDR

Human monocytes/macrophages produce TNF‑α, IL‑1, and PGE₂, mediators that drive inflammation, and controlling their release—potentially via glucocorticoids—has been proposed as a therapeutic strategy. In vitro, purified human monocytes stimulated with LPS alone or LPS plus IFN‑γ generate TNF‑α, IL‑1, and PGE₂. Co‑treatment with IL‑4 (0.1–0.5 U/ml; 12–60 pM) markedly suppressed these cytokines, with mRNA inhibition for TNF‑α and IL‑1, and IL‑4’s effects mirrored those of dexamethasone while opposing IFN‑γ.

Abstract

Stimulated human monocytes/macrophages are a source of mediators such as tumor necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1), and prostaglandin E2 (PGE2), which can modulate inflammatory and immune reactions. Therefore, the ability to control the production of such mediators by monocytes/macrophages may have therapeutic benefits, and it has been proposed that glucocorticoids may act in this way. Purified human monocytes, when stimulated in vitro with lipopolysaccharide (LPS) or with LPS and gamma interferon (IFN-gamma), produce TNF-alpha, IL-1, and PGE2. Cotreatment of stimulated cells with the purified human lymphokine, interleukin 4 (IL-4 greater than or equal to 0.1-0.5 unit/ml; 12-60 pM) dramatically blocked the increased levels of these three mediators; for TNF-alpha and IL-1, the inhibition was manifest at the level of mRNA. Thus, IL-4 can suppress some parameters of monocyte activation and, as for B cells, have opposite effects to IFN-gamma. The effects of IL-4 on human monocytes are similar to those obtained with the glucocorticoid dexamethasone (0.1 microM).