Inhibitory cytokine circuits involving transforming growth factor-beta, interferon-gamma, and interleukin-2 in human monocyte activation.
We have previously reported that transforming growth factor-beta 1 (TGF-beta 1) inhibits interleukin-6 (IL-6) induction by IL-2 and IL-1 in fresh human monocytes. We investigated the effects of TGF-beta 1 on the expression of tumoricidal activity induced by IL-2 or interferon-gamma (IFN-gamma) in human monocytes. We showed that TGF-beta 1 specifically inhibited, in a dose-dependent manner, IL-2-induced but not IFN-gamma-induced monocyte tumoricidal activity. The inhibitory effects of TGF-beta 1 on IL-2-activated monocytes were not caused by down-modulation of the IL-2 receptor beta (IL-2R beta) because the treatment of monocytes with IL-2 and TGF-beta 1 increased IL-2R beta mRNA expression. However, we found that TGF-beta 1 down-modulated IL-2-induced IL-2R gamma mRNA, which may be responsible for the TGF-beta 1 inhibition of monocyte activation by IL-2. The resistance of the IFN-gamma-induced activation to the inhibitory effects of TGF-beta 1 could be caused by the ability of IFN-gamma to decrease TGF-beta 1 receptor expression, as shown by cross-linking experiments. Overall, these results showed that TGF-beta 1 is a powerful inhibitor of IL-2- but not of IFN-gamma-induced activation of monocytes to a cytotoxic stage. This differential effect may be attributed to modulation of cytokine receptor expression.
Espinoza-Delgado
I
I
Medicine Branch, National Cancer Institute, Bethesda, MD.
Bosco
M C
MC
Musso
T
T
Mood
K
K
Ruscetti
F W
FW
Longo
D L
DL
Varesio
L
L
D002478:Cells, Cultured; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D015375:Receptors, Interleukin-2 / Q000235:genetics; D018125:Receptors, Transforming Growth Factor beta / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D007376:Interleukin-2; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D007371:Interferon-gamma